Biology for You - New Updated Edition 0198375816, 9780198375814

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This interactive book is supported by over 1000 resources designed to assist in teaching and learning in preparation for your exams, with resources [aunched directly from the book page Each chapter includes:

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Student Map and Summary Learning Objectives and a Ptenary Checktist and a Revision Quiz Editabte Help and Extension Worksheets*

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PowerPoints to help with common misconceptions and fu[[ colour images of all key diagrams

Animations and Simulations to i[[ustrate dynamic situations Drag-and-drop activities, with Quizzes

And also:

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Teacher Maps and Technician Cards Answers to Further Questions, with Model Answers to examination questions Further support for 'How Science Works' Hetp with Key Skitts

Specification 'Mapping Grids' which show you details of coverage for your particular exam. You can also find these at www.biologyforyou.co.uk

You can personalise your Kerboodle Books by:

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Adding links to retevant websites Drawing, hightighting and adding your own notes

*These worksheets inctude HeIp Sheets, lnvestigation Sheets, Practice Sheets, Diagram Sheets and Research Sheets and also cover some additionaI CCSE and ICCSE topics.

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Nelson fhornes

Text O Gareth Williams 2006, 2011 Original illustrations @ Gareth Williams and Nelson Thornes Ltd 2011

The right of Gareth Williams to be identified as author of this work has been asserted by him in accordance with the Copyright, Designs and Patents Act 1988. All rights reserved. No part of this publication may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopy, recording or any information storage and retrieval system, without permission in writing from the publisher or under licence from the Copyright Licensing Agency Limited, of Saffron House, 6-10 Kirby Street, London, EC1 N 8TS. Any person who commits any unauthorised act in relation to this publication may be liable to criminal prosecution and civil claims for damages. Published in 201 1 by: Nelson Thornes Ltd Delta Place

27 Bath Road CHELTENHAM GL53 7TH

United Kingdom

131415/10987654 A catalogue record for this book is available from the British Library

tsBN 978 1 4085 0920 3 lllustrations by Barking Dog, Mike Gordon, Susan Harrison, Jane Cope, IFA Design Ltd, Jordan Publishing Design, Oxford Designers & lllustrators, Harry Venning, Peters & Zabransky Ltd and Tony Wilkins Cover illustration by Piers Baker Page make-up by Tech-Set

Printed in China by 1010 Printing lnternational Ltd

For Diana, Jill and Gail

Website: The website at www.biologyforyou.co.uk gives you details of exactly which pages in this book you need to study for your particular GCSE examination course. Make sure you visit this website and save or print out the correct sections. They will show you: o which topics you need to learn for your particular examination, and o which page numbers to read in this book.

Introduction Biology For You

is designed to introduce you to

the bosic ideos of Biology. These ideos willshow you how living things ore oble to exist, from the smollest microbe to the lorgest whole, from the tiniest spore to the tollest tree.

These ideos willolso show you how plonts ond onimols interoct with eoch other ond with their environment ond how differences between living things ore possed on to the next generotion ond how they con chonge with time.

Biology for You oims to be interesting ond to help you poss your exoms. It covers the work needed for the Biology content of the new Science GCSE specificotions.

The book is corefully loid out so thot eoch new ideo is introduced ond developed on o single poge or on two focing poges. Words hove been kept os simple ond os stroightforword os possible.

Throughout the book there ore mony simple experiments ond investigotions for you to do. A sofety sign I meons your teocher should give you further odvice (for exomple to weor sofety glosses). Plenty of guidonce is given on the results of these experiments, in cose you don't octuolly do the procticol in school or you ore studying ot home.

Eoch new biologicolword is printed in heovy type ond importont points hove o box drown

oround them. There is o summory of importont focts of the end of eoch chopter. AIso neor the end of mony of the chopters ore 'Biology of work' poges. These show you how Biology con be usefulto us in everydoy life. There ore questions of the end of eoch chopter. They olwoys stort with o simple fill-in-themissing-words question which is usefulfor writing notes or for revision. Other questions check your understonding of the work covered ond need more thought. At the end of eoch of the six moin sections you will find plenty of further questions tqken from recent GCSE popers. Extro sections ot the bock of the book give you odvice on 'How Science Works', on how to do your coursework, revision ond exominotion techniques, key skills ond coreers. I would like to thonk my fomily, Diono, Jill ond

Gqil, for olltheir help ond encourogement during the writing of this book. I hope thot reoding the book will moke Biology interesting ond eosier to understond. Above oll I hope thot using Biology For You willbe fun!

Goreth Willioms

Contents Cells ond life processes 1 Cells 6 2 Diffusion L6 3 Enzymes 26 Biology at work: Enzymes in industry 34 Biology at work Aher uses of enzymes 35 Further guesfions on Cells and life

processes 38

Biologists work with living things from the very smoll to the very lorge...

Humons os orgonisms 4

lnfluenza viruses

Food ond digestion 42 Biology at work: Pictures ot' the gut 59 5 Breothing ond respirotion 62 Biology at work: Tiaining at altitude 75 6 Blood ond circulotion 78 Biology at work: Artit'icial pacemaker and blood pressure 92 Biology at work: Blood trons/usions 93 7 Homeostosis 96 Biology at work: Diabetes 99 Biology at work: The kidney machine and kidney transplants 105 8 Controlond co-ordinotion 108 Biology ot work: ln-uitro fertilisation 725 Biology at work: Controllingfertility 726 9 Support ond movement 129 Biology at work: Sports injuries 135 Biology at work: Arthritis and joint replacement 736 1O Diseose 139 Biology at work: Antibodies ond pregnoncy testing 155 Biology at work: Preseruing food 156 11 Drugs 160 Biology at u)ork: The misuse ot' drugs in sport 168 Further questions on Humans os

Humpback whale

orgonisms

171

Plonts trs orgonisms

20

12 Feeding in plonts 181 Biology at work: Hydroponic.s 195 Biology at work: G/osshouseproduction 796 Biology at work: Plant hormones 799 13 Plont tronsport 202 Biology at work: Monocultures and crop rotations 209 Further questions on Plants as orgonisms 217

Biotechnology ond behoviour 21 Biotechnology 346

Biology at work: The DNA detectiues 243 Biology at work: The human genome project and embryo screening 259 Biology at work: Genetic t'ingerprinting 260 Biology at work: Genetically modified

foods 261 17 Evolution 264 Biology at work: Reclaiming mining tips 274 Further questions on Variation, inheritance and euolution 276

Biology at work: The Chelsea Physic 356 Biology at work: Biofuels 357 Biology at work: Mycoprotein-a food for the future? 358 Behoviour 361 Further questions on Biotechnology and

Garden

Voriotion, inheritonce ond evolution 14 Reproduction 275 15 Voriotion 222 16 Inheritonce 240

Humqns ond the environment 320 Biology at work: Fertilisers 336 Biologg at work: Biodegration of oil and plastics 337 Further questions on Liuing things and their enuironment 340

22

Behauiour 371

Extro sections How Sclence Works 373 Doing your coursework 383 Suggestions for o revision

progromme 387 Revisiontechniques 388 Exominotion technique 390 Key

Living things ond their environment

skills

392 Coreers 394 Index 396

Acknowledgements 400

18 Adoptotion ond competition 282

19

Biology at work: The Eden project 299 Energy ond nutrient tronsfer 302 Biology at work: lntensiue t'ood

production 316

Lookotww*,ot&je-iq_--ifv!..1!::u.

The cellmembrone is the portiolly permeoble membrone in onimol cells The red blood cells in the picture hove been ploced in distilled woter. Their cytoplosm is o strong solution. Woter posses into the cells by osmosis. But onimolcells hove no cellwollto stop them swelling too much - so they burst ! We coll this hoemolysis.

red blood cell

when placed in water the cell

. . and bursts! (haemolysis)

swellsup...

2l :" tf

> A constont blood concentrotion Whot would hoppen if the liquid port of your blood wos too wotery ond dilute ? Whot would hoppen if the liquid port of your blood wos too strong ond concentroted ?

q

t

The red blood cells in this picture hove been ploced in o concentroted solution: Woter hos moved out of their cytoplosm

by osmosis. The cells hove shrunk. Do you think these red blood cells would be oble to do their job properly ? Con you see why it is so importont to keep the concentrotion of our blood constont ? (We will find out more obout keeping our woter content constont in Chopter 7.) The red blood cells in this picture ore in o solution thot is the some concentrotion os their cytoplosm:

Why hove they kept their shope

?

The solutions on eqch side of their cell membrones ore the some concentrotion. So the cells neither goin nor lose woter.

Why doesn't Amoebo burst? Woter enters the Amoebo by osmosis. The woter goes into o controctile vocuole. Eventuolly the controctile vocuole becomes so full of woter thot it moves to the cell membrone ond bursts. The woter hos been removed from the cell.

water enters Amoeba by osmosis

fu,*"q+, 22

water taken into contractile vacuole

contractile vacuole bursts removing water from the cell

)

Active tronsport

vacuole of root hair cell

.,Qn,

Cells con toke up some substonces from dilute solutions ond keep them in high concentrotions

Look of the concentrotion of mognesium ions in the root hoir cell: solution

Look of the concentrotion of mognesium ions in the soil solution:

ffi

Which woy would you expect mognesium ions to move by diffusion ? Sometimes cells con keep hold of porticles ond not let them diffuse out. Whot's more they con even toke in more porticles ogoinst o concentrotion grodient.

Look ot the histogrom: It shows the concentrotions of some solts inside the cells of o woter plont ond outside in the woter.

4000

These solts connot hove been token in by diffusion They ore token in ogoinst o concentrotion grodient They ore token in by octive tronsport. Active tronsport needs energy from respirotion

3000

B f_l

inside cell in water outside

o

=o

2000

E

'1000

to moke it hoppen.

Active tronoport is the uptoke of porticles by cells ogoinst o concentrotion grodient. Active tronsport needs energy.

NaKMgCaCl

sodium potassium magnesium calcium chloride The concentrations of salts found inside and outside the cells of a freshwater plant

Sugors con be obsorbed from the smoll intestine ond

from the kidney tubules by octive tronsport. particles

4.'

outside cell

outside cell

o o o O1

carrier protein inside cell

Cariler protein takes up particles on outside of membrane

The corrier protein uses energy to tronsport molecules or ions ocross the membrone. This energy comes from respirotion inside the cell. Poisons like cyonide con stop respirotion. Do you think thot this would stop octive tronsport too

Carrier protein releases particles on inside of membrane

?

inside cell

Summory o

Molecules move from o high concentrotion to o lower concentrotion by diffusion.

o

The greoter the difference in concentrotion, the foster the rote of diffusion.

o

Food ond oxygen diffuse into cells. Corbon dioxide ond wqste substqnces diffi.rse

o

Woter posses into plont cells by osmosis. A plont cell thot is full of woter is turgid. If plont cells ore ploced in o shong solution, woter posses out by osmosis. As the vocuole shrinks the cellmembrqne eventuolly peels owoy from the cell woll - the cell is plosmolysed.

o

If onimql cells ore put into q weok solution they toke in water ond burst.

molecules from o dilute solution into o more concenkoted solution through o portiolly permeoble membrone.

o

Porticles con be token into o cell ogoinst o concentrotion grodient. This process needs energy so is colled octive tronsport.

Questions

4.

o) Is o cell membrone permeoble, impermeoble or portiolly permeoble ? b) Is o cellwollpermeoble, impermeoble or portiolly permeoble ? c) These two chips were cut from o pototo. Eoch toos 50 mm long. One wos put into woter ond the other wos put into strong sugor solution. Use your ruler to meosure eoch chip.

out.

o

)

Osmosis is the movement of woter

1. Copy ond complete

:

Molecules move from

o..

..

concentrotion to

o .... concentrotionby....

.

Osmosis is the movement of . . . . molecules

from

o....

solution into o more

....

solution

ocross o . . .. permeoble membrone. When plont cells toke up woter by osmosis they become . .. . . Turgid cells help support ports of o plont like the . . . . . If plont cells lose woter the stem locks support ond . . . . . If plont cells lose o lot of woter the cell . . . . peels owoy from the cell . . . . ond the cell is

chip A

soidtobe..... 2.

o) Which diffuses foster, o liquid or o gos Why is this ?

b)Whot would heoting do to the rote of diffusion of o solt crystol in woter c) Whot things diffuse: i) into cells ii) out of cells ?

3.

The test-tube contoining ogor jelly ond blue dye wos set up os shown in photo A A

chip B

?

i) Which chip wos put in woter?

?

Exploin your onswer. ii) Which chip wos put into strong sugor solution ? Exploin your onswer.

5.

T

Photo B shows its oppeoronce ofter o week. o) Exploin os fully os you con whot hos hoppened to the blue dye. b) WhV did it toke o week for this to hoppen

o) Exploin why red blood cells burst if they ore put into woter.

b) Exploin why Amoebo does not burst when

?

put into woter. c) Some plont cells ore put into o solution. They neither toke up woter nor lose woter. Whot con you soy obout the strength of the cell sop ond the externol solution ?

6.

7. Two freshly cut pototo

The experiment wos set up os shown

chips were set up os

shown.

AB glass tube with scale marked in mm

150

weight

uid chip pin

100

starting level of

50

sugar solution

ne

Eoch wos covered with o colourless liquid. o) Whot liquid wos used in A ?

water

b) Exploin why the chip in A wos oble to support the weight. c) Whot sort of liquid wos used in B ? d) Exploin why the chip in B bent under the weight.

Visking tubing concentrated sugar solution

8. The level of the liquid in the tube wos meosured every minute. The results ore shown in the groph

Botches of 10 pototo discs were weighed ond then ploced into one of 10 different concentrotions of sugor solution. After 30 minutes the pototo discs were removed ond re-weighed. Their percentoge chonge in moss wos worked out. The results ore shown in the

groph:

200 cu

B6

tso

gain

Oc

oB

5

roo

-o ca

.9) 0)

percentage

rlll ],]l

50

change in

,,1

lrll

weight

c

-1 loss

12345678 time (minutes)

o) Exploin why the liquid rose in the tube. b) Whot wos the level of the liquid ofter 4 minutes ? c) How much longer did it toke for the liquid to reoch the top ? d)Would the liquid toke longer to reoch the top if the sugor solution wos weoker ?

Exploin your onswer.

0.1 0.2 o)

whot process

;:","J1[

0.3

.4

:'^::;:[,,

of the pototo discs ? b)Whot would the pototo discs be like ot X? c) Whot other differences oport from weight would you be oble to observe between the discs ot X ond Y ? d) Use the groph to find the concentrotion of sugor solution thot would couse no chonge in the weight of the pototo discs.

Further questions on poge 38.

25

il''ir.

'

ttIrIY

chapter 3

$

Thousonds of chemicol reoctions toke ploce in our cells. We need these reoctions to hoppen quickly to keep us olive. Luckily for us there ore chemicols colled enzymes. Enzymes moke reoctions hoppen of o much foster rote. Chemicols thot speed up reoctions ore colled cotolysts. Since enzymes speed up chemicol reoctions in our cells, they ore often colled biologicol cotolysts.

Breokers ond builders Enzymes come in two moin types

Computer model of an enzyme

Breakers Sometimes we need to breok down lorge molecules into smqller ones. Breoker-enzymes speed up these reoctions. This is importont in digestion when lorge food molecules ore broken down into smoll ones so thot we con use them.

Builders

A

L\

D tl

A

))

arFD

o

In other reoctions smoll molecules ore joined together to moke lorge ones. Builder-enzymes speed up these reoctions These enzymes build importont molecules inside our cells. ),

t(

Enzymes ore protein molecules mode up of long choins of omino ocids. These long choins ore folded to produce o

speciol shope colled the octive site. Other molecules colled substrotes fit into the octive site ond o reoction tokes ploce. This is how o breoker-enzyme works:

enzyme

substrate

T:,.Jrleitl

enzyme

Use the diogrom below to exploin how o builder-enzyme works

.i,.,r1;,26

products released

l)

)

Enzymes ore porticulor ..

.

All enzymes hove five importont properties

l.They ore oll proteins. 2. Eoch enzyme controls one porticulor reoction. 3.They cgn be used ogoin ond ogoin. 4. They ore offected by temperoture. 5.They ore offected by pH.

substrate A

Look ot the diogrom:

substrate B

Use it to exploin why eoch enzyme willonly work on one porticulor substrote. Does the shope of the octive site decide this ?

enzyme

Which substrate f its the active site ?

Why is only o small omount of enzyme needed to control o reoction ?

,C

,e

Enzymes con be used over ond over ogoin.

Once the products leove the octive site, more substrote con enter. So the enzyme willkeep on working untiloll the substrote is used up. Just o little enzyme goes o long, long woy

enzyme

substrate enters active site

products released

!

An enzyme can act on lots of substrate

Enzymes in digestion Enzymes breok down lorge food molecules into smoller ones inside your gut. This is colled digestion. Why do these food molecules hove to be broken down into smoller ones?

{

Look ot the diogrom: The woll of the gut works o bit like o net. Whqt sort of molecules con get through ? Two lorge food molecules ore shown below. Copy cnd complete these sketches to show whot they would look like after enzymes hqve digested them.

Only small molecules can get through the gut wall into the blood

starch molecule (a carbohydrate) glucose molecule

digestion by carbohydrase

bond holding two glucose molecules together

protein molecule

digestion by protease amino acid molecule

-

',.,:8.{J=':.

The fostest enzyme in the west

!

Pototo cells contoin on enzyme colled cotqlose. It speeds up the breokdown of hydrogen peroxide into woter ond oxygen. Do you remember how to test for oxygen? A Add o smoll piece of pototo to 5 cm3 of eye protection hydrogen peroxide in o test-tube. CARE: hydrogen peroxide is corrosive ond on irritont. Test the gos which is given off with o glowing splint.

Experiment

3.7

Fost t'roth pieces pototo Cut two of to the some

size.

A

Put one piece into o boiling-tube contoining eye protection 5 cm3 of hydrogen peroxide.

CARE: hydrogen peroxide is corrosive qnd qn irritont. Use o ruler to meosure the highest point thot the froth gets to in the tube.

Now do the some with the second piece, but this time chop the pototo up into smoll pieces first.

o

Which tube mode the most froth? Why do you think this is?

o Where is the enzyme found in this reoction ? o Wos the enzyme o breqker or o builder?

Cotolose is found in mony living cells. It breoks down hydrogen peroxide to woter ond oxygen, thot's where the bubbles come from.

Hydrogen peroxide

cotolose

woter

t

oxygen

Chopping up the pototo releoses more cotolose from the cells Cotolose is the fostest enzyme known. Hydrogen peroxide is often formed os o product of reoctions in cells. It con be poisonous if it builds up. Why do you think cotolose hos to work so quickly ?

28

The right enzyrrne for the job There is o corbohydrose enzyme in our solivo. Whot type of food does it oct upon ? The corbohydrose in our solivo is colled omylose It breoks down storch to sugor: Storcn

omvlose -----+

Sugor

Experiment 3.2 The effect of amylase on starch Storch turns iodine solution blue-block. When storch is broken down it will not turn

iodine blue-block.

add one drop of starch alone to this well

Put one drop of iodine into eoch well on o spotting tile.

add one drop o, starch/1% amylase to this well

0 min

Add 1 cm3 of 1 % omylose solution to 5 cm3 of 1% stqrch solution in o test-tube.

Start the stop-clock immediately. At the times shown in the diogrom toke o drop out of the testtube ond qdd it to the iodine on the spotting tile. Wash out your dropping pipette between each sample.

1 m 30

secs

2 min

3 m 30

secs

4

min

starch alone

mixture straight after mixing

6lack

0lack

add one drop of starch/1 % amylase to this well after 30 secorids

30 secs

2 m 30

1 min

o o

secs

3 min

4 m 30 secs

5 min

mixture after 30 secs

mixture after 1 minute

(starch presont) @qcn_Weaem) after 11/, mins

atter 2 mins

after 21l2 mins

atter 3 mins

after 31/, mins

after 4 mins

after 41l, mins

after 5 mins

Record your results in o toble like this:

o o o

o

How did you know when ollthe storch hod gone ?

How long did it toke before ollthe storch wos broken down? Whqt did the stqrch form when it wqs broken down? How could you prove this?

Could o proteose hove broken down the storch

?

protease

protein

Remember, on enzyme is specific. It con only control one kind of reoction carbohydrate

Corbohydroses c(m only breok down corbohydrotes. Proteoses con only breok down proteins. Liposes con only breok down fqts.

fat

)

Hotting up

Enzymes ore offected o greot deol by temperoture.

q)

This groph shows the effect of increosed temperoture on on enzyme-controlled reoction:

.C

Look ot the groph. o How fost is the reoction going of 10 "C ? o How fost is the reoction going ot 20"C? o How much foster is the reoction of 20 "C thon ot 10 "C ?

9

E 0)

o-

o f

oO)

E i

E

.o o (!

2.O

0)

o o

At whot temperoture is the reoction going fostest? Why do you think the reoction goes foster os the temperoture increoses ? (Hint: whot hoppens to molecules when they worm up

o o (u

0

10 20 30 40

?)

50

temperature ("C)

o How fost is the reoction going of 50'C ? o Whot do you think is hoppening to the enzyme ol high temperoture

? enzyme

substrate

As you know, oll enzymes ore proteins.

At high temperotures the speciol shope of the protein choin breoks down. The octive site is chonged, so the substrote no longer fits. We soy thot the enzyme hos been denotured ond it no longer works.

Enzyme denatured fits the active site

lnuestigation 3.3 Effect of temperoture on enzyme oction Plon qn investigotion into the effect of temperoture on the qction of on enzyme. You could use omylose.

o Whqt temperotures will you use ? o How willyou tell how fost the reqction is going? o How willyou know when the enzyme hos finished working? o How will you show your results? o Check your plon with your teocher before you begin. Enzymes ore useful in industry. They con mqke chemicolreoctions toke ploce of lower temperotures. Why do you think this soves money ? (For more obout enzymes in industry see Biology ot Work, poge 34.)

ffigf,rfii. ao

- substrate

no longer

)

Enzymes ond pH

6.0

An enzyme is offected by how much ocid or how much

olkoli

o 5.0

is present.

f C

Mony enzymes work best in neutrolconditions, but some prefe'r ocid ond some olkoli.

oE *9 oX

Look ot the groph showing the oction of enzymes X ond Y:

o At whot pH does enzyme X work best? o At whot pH does enzyme Y work best? o Whot hoppens to the oction of enzyme X obove pH 5.5 ? o Whot hoppens to the oction of enzyme Y below pH 5 ? The octive site of on enzyme con be chonged by very ocid or very olkoline conditions. How do you think thot this could reduce the rote of o reoction

4.0

en 2

o) E

1.0

enzyme

0 1 2 3 4 5 6 7 8 9pH +acid neutral *alkaline ?

3.4 The effect of pH on the action of a protease Exposed photogrophic film contqins block groins of silver. These ore stuck on by o loyer of gelotin. Gelotin is o protein. Experiment

You con investigote the effect of o proteose on gelotin ot different pHs. Set up the experiment os shown in the diogrom: water

After 30 minutes, toke out eoch strip with tweezers. Gently rub the film, between your finger ond thumb, under o cold top. If the gelotin hos been digested, the film will turn colourless

tubeA

tube

B

enzyme enzyme

37'C tube C

enzyme solution solution solution and water and acid and alkali

tube D boiled enzyme solution and waler

Record your results in o tqble.

o In which test-tubes did the proteose breok down gelotin ? o Whot effect does boiling hqve on the oction of the proteose? o In which conditions of pH does the proteose work best? o Why do you think thot the test-tubes were kept ot 37'C? This proteose breoks down proteins to omino ocids in the

smollintestine. It works best ot o pH of obout 8.5 ond ot 37 "C. Like other enzymes, it is denotured of high temperotures.

Computer model of a protease

: ,Sl

,ittilili

Proteoses breok down the proteins into omino ocids. The omino ocids ore smoll enough to get through the

gut woll ond into our blood. These omino ocids join our body's omino ocid pool. When we grow we toke omino ocids out of this pool. Enzymes join these omino ocids to moke new proteins.

#sryr Y%sF

*"i*+

amino acid Pool

oarticular amino acibs are selected

. . . and used to make new proteins

Experiment 3.5 Building stqrch t'rom glucose Green plonts moke glucose during photosynthesis. Mony plonts store this glucose os stqrch. Pototo hos qn erwme thot chonges glucose into stqrch

a

aooo oo aOOO

glucose

enzyme

+

molecules

starch molecule

First you hove to moke on extroct of pototo enzyme

Grind o smqll piece of pototo with 5 cm3 of woter. Centrifuge the extroct for 2 minutes. Now test o drop of the extrqct with some iodine to moke sure thot the solution is storch-free. You will use 1cm3 syringes to deliver drops of liquids.

Now get your iodine reody. Moke up row A ond immediotely odd one drop of iodine to the first well on the spotting tile. Repeot ot the times shown. Copy the toble ond record your results in words or with croyons. Storch forms when the iodine turns blue-block. o How long did it toke for storch to form in row A?

B

c

Row

o Willrow B moke storch without ony enzyme? o Wi[ row C moke storch without ony glucose? o Would there be ony storch in pototoes without this builder-eruyme? Why not?

,,l ,li

32

2 drops glucose monophosphate, 2 drops potato

extract

Now set up rows B qnd C using cleon syringes. Repeot the procedure.

2 drops glucose monophosphate, 2 drops water

c

Time (minutes)

To each

well add: A

,),),)' , )r, )r, ,,

2 drops water, 2 drops potato

extract

0

5

10

15

complex chemicals

Breoker-enzymes breok down complex chemicols into simple ones. At the end of the reoction, the enzyme ond these simple chemicols ore mixed together. In industry, it con be very expensive to seporote the enzyme from these simple chemicols.

t

glass tube enzyme immobilised on resin bead

!a La \

O

complex chemicals added

@

immobilised enzymes breakdown complex chemicals

@

simple chemicals Ilow out

We solve this problem by fixing the enzyme to smoll resin beods. In this form, we soy thot the enzyme is immobilised becouse

it con not move. The resin beods ore pocked into o gloss tube. The complex chemicol is poured in ot the top. As it trickles through the beods, the reoction tokes ploce. Simple chemicols run out of the bottom of the tube.

tta'

t

simple chemicals

Lumpy ice creom Sucrose forms crystols more eosily thon simple sugors like glucose This con couse sweet foods, like ice creom, to go hord ond lumpy. Monufocturers use yeost enzyme to breok the sucrose down into simple sugor molecules.

"E*! sucrose molecules

+

enzyme

aoo O aa oo oo ao simple sugar molecules

Experiment3.6 Changing sucrose into simple

sugors

1. First moke your resin beods. Mix some yeost poste with some sodium olginote poste in o beoker.

2

H

Add drops of the mixture into colcium chloride solution. 2. Wosh the beods (cooted with yeost erwsme) in q sieve.

3

3. Fill o gloss tube with the beods, leoving q spqce ot the top. Mqke sure thot the top on the gloss tube is closed. 4. Test the sucrose solution with o glucose-detecting strip. No glucose should be present. Pour the sucrose solution into the glass tube ond leove for 5 minutes.

4

5

5. Open the top ond run out the solution into o cleon beoker. Test the solution with onother glucose-detecting strip.

o

r o o

Does the second glucose-detecting ship furn purple Why does this hqppen ?

?

How do you think the sucrose hos been chonged to glucose Where wqs the enz.)me in this experiment? Why cqn this enzyme be used ogoin?

?

33.,: ,....,ii:.-

.:. .: ",i',ri' ,:1

}

Biologiy qt work: Enzymeo in industry Enzymes hove become very importont in industry. They ore versotile ond for more efficient thon other cotolysts. They work ot relotively low temperotures. So this reduces fuelcosts, moking them cheoper to use. Also enzymes con be reused ond therefore they ore only needed in foirly smoll omounts.

Biologicol woshing powders Biologicol woshing powders contoin proteoses ond liposes. These breok down the protein ond fot stoins such os grime ond sweot. These woshing powders work of quite low temperotures. Whot would hoppen to these enzymes if they were boiled ? Enzymes ore unstoble ot high temperotures ond of extremes of pH. But there ore some bocterio thot con thrive ot high temperotures, like those found in hot springs ond thermolvents on the oceon floor. These bocterio contoin thermostoble enzymes.

This meons they ore unoffected by high temperotures. Scientists hove been oble to isolote the genes thot code for these enzymes ond tronsfer them into the bocterium Bacillus subtilis. The bocterium then multiplies, in o fermenter, producing lots of the enzyme subtilisin for commerciol use. Subtilisin is o proteose thot works best in olkoline conditions. It con tolerote the olkoline phosphotes in woshing powders. It is octive ot 60 "C so con be used in o wide voriety of wosh progrommes. lnuestigation

3.7

The effects ol different factors on enzyme action

How con you moke enzyme reoctions foster or slower

?

Investigote the effect of one foctor on the oction of o biologicol woshing powder.

Which foctor will you look ot ? How will you judge how well o powder contoining enzymes works ? You could compore how well the stqins hove been removed. Plon o foir qnd sofe test. Show it to your teocher before you stort.

Alternotively you could compore the oction of biologicol ond non-biologicol woshing powders.

o o

o

)

Biology of work: Other uses of enzymes Sweeteners There is o worldwide demond for sweeteners moinly in confectionory ond fizzy drinks. Troditionolly sucrose (the sugor you put in your teo) hos been used. It is extrocted from sugor beet or sugor cone. In recent yeors o sucrose substitute, high fructose syrup, hos been introduced since it is cheoper to produce. Fructose is sweeter thon sucrose ond con be mode from storch, o relotively obundont ond cheop food stuff. Amylose is first used to convert the storch to glucose. Then isomerose converts the glucose syrup into fructose syrup (isomerose is used os on immobilised enzyme, see poge 33) Fructose, being much sweeter thon sucrose, con be used in smoller quontities in slimming foods.

amylase GLUCOSE rsomerase

Do you like those chocolotes with the soft, gooey centres ? Hove you ever wondered how they ore mode ? The chocolote is poured over o solid mixture contoining sucrose ond o corbohydrose enzyme. The chocolqte sets ond the enzyme breoks the sucrose down into glucose ond fructose. These smoller sugors ore much more soluble thon sucrose, ond dissolve in the smoll omount of woter in the originol mixture.

Extrocting fruit juice

3.8

Getting the juice Cut on opple in holf.

Experiment

Chop eoch holf into smollpieces ond put them into seporote beqkers. Pour 10 cm3 of pectinose over the opple in beoker A ond 10cm3 of wqter over the opple in beoker B. Ploce both beokers in o woter both ot 40'C for 20 mins. Filter the juice from eoch of the beokers of opple pieces.

o Which of the opple pieces will moke most juice ? o How does the pectinose releose this juice from the opple o Why were 10 cm3 of woter odded to beoker B ?

cells ?

Some other uses of enzymes: Proteoses ore used to tenderise meot ond remove hoir from skins. Proteoses ore olso used to 'pre-digest' the protein in boby food. You con find out obout the enzymes used to moke cheese ond yoghurt ond those used in brewing ond boking in Chopter 21.

A

B

Summory o

Enzymes speed up chemicol reoctions

o An enzyme is unchonged

inside cells.

o

Breoker-enzymes split up lorge molecules ihto smoller ones.

o

Builder-enzymes join smoll molecules together to moke lorge ones.

o

)

Enzymes work foster os the temperoture increoses up to 40'C, but eventuolly

they ore denotured ot obout 60'C.

o

r

Questions

4.

Eoch enzyme works best of o porticulor pH. Enzymes ore extensively used in industry becouse they ore cheop ond more effective thon other cotolysts.

Lipose is on enzyme thot breoks down fots. We con use on indicotor to follow this

:

o) Enzymes .... up the rote of chemicol .... b) Enzymes ore . . . . becouse they only work on one substrote. c) The substrote fits into the . . . . site on the

surfoceof the..... d)With on increose in .. . . , the rote of reqction .. .. . But eventuolly o temperoture is reoched which .... the

enzyme. e) Enzymes con be re-used, so only .... omounts ore needed.

2. o) To which group of chemicol

compounds do

enzymes belong?

b)Which enzymes work on i) corbohydrotes ii) proteins iii) fots? c) Nome the products which ore formed in eoch cose.

3. An enzyme hqs on 'octive

site' on its surfoce on which the reoction tokes ploce. Use the ideo of on octive site to exploin : o) Why on enzyme is specific for o porticulor

substrote. b)WhV enzymes ore denotured ot high

temperotures. c) Why on enzyme con be used ogoin ond ogoin.

36

o

Enzymes ore specific. They will only oct on one porticulor substuote. This is becouse the substrote hos to fit the ena1me's octive site.

1. Copy ond complete

ofter the reoction,

so con be used mony times. This is why only o smoll omount of enzyme is needed.

reoction. The indicotor is red to stort with but turns yellow when ollthe fot hos been broken down. Test-tube 1

2 3 4 5

Temp. "C 0 10

40 60 100

Original

Final

colour

colour

red red red red red

orange yellow orange

red

red

Look ot the results: o) At whot temperoture does lipose work best ? b)Why do you think the colour did not chonge in test-tube 1? c) Why do you think the colour did not chonge in test-tube 5 ? d) Predict whot you think would hoppen if you wormed test-tubes 1 ond 5 up to 40 "C. Try to exploin your prediction.

5. A number of foctors con olter the rote of on enzyme-controlled reoction. Soy whot eoch of the following would do to the rote of reoction, ond give your reosons: o) An increose in enzyme concentrotion. b)A decreose in temperoture. c) A lowering of pH.

6.

The following experiment wos set up to investigote the oction of proteose on egg-white When enzymes breok down the protein in egg-white, it chonges from cloudy to cleqr. A

enzyme A

B

t

E

.9

enzyme B

o

(d

o 2 cm3 water 5 cm3 egg-white

1 cm3 water '1

This groph shows how pH offects the rotes of two enzyme-controlled reoctions.

cm3 pepsin

o 6

5 cm" egg-white

o) Exploin why the contents of test-tube A went cleor ofter 15 minutes. b) Exploin why the contents of test-tube B stoyed cloudy ofter 15 minutes. c) How could you increose the speed of the reoction in test-tube A ? d)Whot do you think the egg-white protein wos broken down to form ?

7. The groph

shows how temperoture offects on enzyme- controlled reoction.

0123456789pH d)Which enzyme works best in ocid conditions

?

e) Which enzyme works best in

olkoli conditions

?

f) Whot does the groph tellyou obout the range of pH over which eoch enzyme is octive

?

8. In 1989 o new fot-digesting

enzyme wos

found in o fungus. This enzyme works best ot o pH of 7.5. The enzyme con oct of low temperotures ond, ofter o few doys, breoks down into corbon dioxide, nitrogen ond woter.

c

o o 0)

=

o

z

(!

'environmentolly friendly'

X

10

20 30

40

50

temperature ("C)

o) Exploin whot is hoppening: i) between X ond Y

ii)

o) Give two reosons why this enzyme is now used in woshing powders. b)Why do you think thot this enzyme is

between

Y ondZ.

b) Suggest how increosing the temperoture offects the rote of reoction of the enzyme. c) Whot is hoppening to the octive site of the enzyme of the higher temperotures ?

?

c) Why would o woshing powder of high pH or low pH be difficult to hqndle ?

Further questions on poge 38.

Further questions on Cells ond

)

Cells

I

chloroplasts

The toble which follows shows o function of eoch of these orgons. Copy the toble qnd motch the correct function to eoch orgon by writing the correct letter in eoch box. The first one hqs been done for you.

PLANT CELL

cytoplasm

Letter

Function cell wall

Stores waste fluid called urine

H

Breaks food down into smaller chemicals Can contain a developing fetus

Controls other organs Filters the blood to help remove waste Helps oxygen to enter the blood and carbon dioxide to leave

nucleus ANIMAL CELL

vacuole

Helps to move air in and out of body

cell membrane

Pumps blood through the body

o) Use only the drowings obove to copy ond complete the toble below to show three differences between plont ond onimol cells.

Takes water from food into the blood stream

tgl

t3l Plant cells

Animalcells

1

3.

The diogroms below show five cells, some from qnimqls ond some from plonts. Note thqt the diogroms ore not oll drown to the some

2

scole.

b) Whot is the job of eoch of the following ports of o cell:

o

i) nucleus ii) cellulose cellwoll iii) cytoplosm iv) cell membrone? [a]

2.

i) ii)

Whot substonce is contqined in the chloroplosts? Why is this substonce importont to oll living things? [2] (WJEC) Letter

Organ

A

Brain Heart Lung Diaphragm Stomach Large intestine

B D E

F G

.

38

D

c

The key below lists orgons of the humon body.

c

'"1 fii''

B

A

3

c)

(EDEX)

H

Kidney Bladder

I

Uterus

Note: although a question may be marked (EDEX) etc,

E

The cells ore speciolised to corry out certoin functions. The list below gives the functions of these five cells.

1. obsorbs solts ond woter from the soil 2. kills bocterio 3. mokes food by photosynthesis 4. cqrries elechicql impulses 5. shortens to bring obout movement it will olten be relevant to other examinations as well

Further questions on Cells ond life processes o)

i) ii)

Copy ond complete the toble below by motching the cells with the letters from the diogroms. Complete the column ii) of your toble by motching the cells with the correct number from the list of functions. t4l

Name ol

the cell Muscle cell

i)

ii)

Letter of diagram

Number ol

E

5

5.

Lengths of Visking tubing were set up os follows: A contoined 1% storch ond omylose; B contoined 1% storch ond boiled omylose. Both were left in woter of 30 "C for one hour. They were then ploced in beokers of dilute iodine solution ond left for five minutes os shown below. Iodine solution con poss through Visking tubing.

function

1% starch solution +

Palisade cell

Visking

tubing

1olo starch solution + boiled amylase

Root hair cell

Sensory neurone White blood cell

b) Choose two of the cells shown in the diogrom ond for eoch one describe how its structure ollows it to perform its function

efficiently.

t2l

A

iodine

B

(EDEX)

o) Whot colour would you expect to see

F Diffusion

inside

4.

ii) B?

i)

The diogrom shows two pototo cubes, X ond Y thot were ploced in distilled woter for one hour.

A

b) Exploin whot hos hoppened inside Describe o test to prove your c)

i) explonotion ii) Stote the expected results.

XY

A.

t2l t2l t2l t1l

d)Whot oppeors to be the effect of boiling the omylose

o) Exploin why both cubes goined in moss

ofter one hour. t3l b) Copy the toble ond put o tick in the row thot correctly describes the chonge in moss for cube X compored to cube Y. Mass of water absorbed in g

Percentage increase in mass

more

lower

less

lower

less

hiqher

more

higher

Tick

6.

?

t1l

(WJEC)

A teenoge boy wos pulled out of the seo ofter he got into difficulty. The boy coughed up some seo woter ond the lifeguord insisted he wos token to hospitolfor observotion. The boy soid he felt fine so the lifeguord exploined thot there is o donger of secondory drowning if you inhole seo woter ond it stoys in your lungs. After o short time the oir socs could fill with woter ond goseous exchonge would be impossible.

t1l

Exploin os fully os you con, using scientific terms, why the boy's oir socs could fillwith woter ofter he is token to hospitol. (AOA)

tsl

(AOA)

39

questiona on Cells ond 7. A student corried out on investigotion on the effects of vorious sugor solutions on rods of pototo tuber. The student used o cork borer to remove the rods which were genfly blotted ond weighed.

8. A pupil set up the opporotus shown in the dioqrom. glass concentrated thistle funnel

Eoch rod wos then ploced in distilled woter or in one of severql sugor solutions of different concenbations. After 2 hours the rods were removed, gently blotted ond reweighed. The resulh, expressed crs o percentoge chonge in mctss, ore shown in the toble.

sugar solution

partially permeable mernbrane

dilute sugar solution

o) Whot hoppens to the height of the sugor

solution in the

funnel?

t1l

b)F;ploin why this hoppens. Conccntretion of sugar solutlon ln arbitrary unlts

You moy use the diogrom below to help ln mass

-7

Plot o line groph of the dotq on o sheet of groph pqper. Put concenfuotion of sugor solution in orbitrory units on the horizontql oxis ond percentoge chonge in moss on the

trl

c) Whqt else might the student hove meosured to investigote the effect of the sugor solutions on the d)Some people sook solqd vegetobles, especiolly lettuce, in solt woter to remove onimols such os slugs ond greenfly. However, if the lettuce is left too long in the solt wqter the leqves become limp. Exploin why the lettuce leoves become

tll

i) limp. nl ii) Suggest how the lettuce leoves could (EDEX) be rnsde crisp ogoin. ttl

:l;

W&+-+=.,,,,,,..,,,

concentrated

morecures

*"

!l,n?[. ," thistle tunnel

@@J\

verticol oxis. t3l i0 From the groph, work out the concenhotion of sugcr solution which would result in no chonge in mqss of the pototo tuber. t1l b) Nome the process which cquses the moss of the pototo to chonge in this experiment.

40 ,:..1,. r: rl:rrl. l

mol€cules

P ),/ "@"b'' : :@.'.@'.' ....' .. .:.@...:@ l' pailialy permeable 9" 3: 3 .;-.;2 :x '. .l membrane '..:. @

-10

rods?

sugar

t

-1

1.00 1.50

i)

@

. : : warer

+8 +4

0 (distilled water) 0.25 0.50

o)

with your onswer.

Percentage change

dilute sugar solution in beaker

t4l

)

(AoA)

En4rmes

9. o)

i) I Whut nome is given to on en4y'me which cotolyses the breokdown of protein? t1l Whot product is formed when protein

ii)

is broken down by the

ervyme? tll

The toble shows the effect of pH on the octivity of on enzyme which cotolyses the breokdown of protein. pH Rate of formatlon of product

ln mmol per mlnute

1.0

2.0 3.0

10.5 23.0 10.5 2.5 0.0

b) Drow o groph of the dqto in the toble. c) The enzyme is produced bythe humon digestive system. At whot pH does this enzyme work

i) best? ttl ii) Suggest which port of the digestive system produces this enzyme. ttl d) \A/hy is it necessory to breok down proteins (AOA) in the digestive system? t3l

Further questions on Cells qnd life processes 10. Sucrose con be digested to give glucose ond fructose. This reoction is speeded up by the enzyme sucrose. Sucrm

^ Sucrose----lGlucose

* Fructose

o) 'Disocchoride' is the term used to describe sucrose. Whot term is used to describe glucose?

t1l b)A student corried out on investigotion into the effect of increosing the concentrotion of the enzyme sucrose on the rote of this reoction. He kept the concentrotion of sucrose constont. He used six different concentrotions of the enzvme (sucrose) ond for eoch of these he meosured the time token for the sucrose to be completely digested. He corried out oll the reoctions of 40 "C. The student's results ore shown in the toble below. Enzyme sucrase concentration (%)

Time taken to digest

0.10

950

0.2s

600

11. Some cots become ill if they drink cow's milk. Scientists hove found out thot the milk sugor, loctose, is responsible for the illness. In the pet food industry, loctose is odded to milk to chonge the loctose into simple sugor os glucose, but loctose is on expensive substonce.

The loctose is mixed with o type of jelly ond smollbeods ore produced which ore put into o long tube. The milk is poured into the tube ond collected ot the bottom. The diogrom shows o loborotory model of the industriol process. Cold milk

lactose Beads containing lactase

sucrose in seconds

0.50

470

1.00

290

1.50

225

2.00

160

Gauze Tap

Milk containing glucose

i)

Plot o groph of these results. Join the points with stroight lines. tsl ii) Describe how increosing the concentrotion of the enzyme (sucrose) offected the time token for the sucrose to be digested. t2l c) i) Suggest why he corried out oll of the reoctions ot 40 "C. t1l ii) Describe one woy thot he could keep the temperoture constont (ot 40'C).fi1 d)The student then repeoted this experiment, first of 20 "C ond then ot

o) Whot sort of substonce is loctose? t1l b) Stqte two odvontoges of putting the loctose into beods. t2l c) Suggest one modificotion which would speed up the chonge of loctose to simple

sugqr.

tll

d)After using the beods for severol doys the monufocturers find thot there is still loctose in the milk product ond they hove to reploce the beods. Exploin why the loctose does not work ofter severol

doys.

tll

(AOA)

90"c. Suggest whot would hoppen to the time token for the sucrose to be digested ot 20'C ond 80 "C. In eoch cose give o

reoson for your

onswer. t4l

(EDEX)

47

ail

chopter 4

Your body is mode up of chemicols. You get these chemicqls from the food thot you eot. Whot do you think your body uses your food for?

o

For energy

You need food to work your muscles ond other orgons. Your food is the fuel thot keeps you going. Just like o cor won't stort without petrol, your body won't work without food.

ls

o

For growth ond repoir As you groq you moke new cells. You olso need to reploce old or domoged cells. You moke new cells from chemicols in your food.

o

To stoy heolthy

Lots of reoctions toke ploce in the cells of your body. Chemicols in your food ore needed for these reoctions. So nutrition meons getting food to provide energy qnd substonces needed for growth ond repoir.

Whot's in the food we eot? These ore some of the nutrients thot ore in our food

proteins carbohydrates fats vitamins minerals fibre

water

Some foods moy hove o lot of protein in them. Other foods moy not hqve much protein ot qll. Some foods moy hqve q lot of corbohydrote or fot. Different foods hove different vitomins ond minerols. If we qre to stoy heolthy our bodies must hove

o o

enough food o vqriety of foods - so thqt our body gets oll the different things it needs.

We need o heolthy,

bolonced diet.

Remember qlso thot q bolonced diet will chonge depending upon o person's oge, gender ond how octive they ore. til!.

,

42

Which is the better balanced meal ?

)

Proteins

Your body is mode up of billions of cells. These cells ore mode moinly from protein Proteins ore mode up of the elements corbon, hydrogen ond oxygen, but they olso contoin nitrogen (N) ond mony hove sulphur (S). When you grow your body needs protein to moke new cells. Some protein-1ch foods Your body moy need to reploce old or domoged cells. You need enough protein in your food for this os well. Proteins ore mode up of lots of omino ocids. There ore obout 20 different types of omino ocids Here ore two different proteins: Con you see whot mokes them different?

Hoemoglobin, enzymes, ontibodies ond some hormones (e.g. insulin) ore soluble proteins Kerotin is o fibrous protein found in the skin ond hoir.

(-J digestion

Og r+> C

->

a AO

(\ ovc

amino acid pool

when the proteins are digested they are split up into single amino acids amino acids from the pool are now used to make new proteins

two proteins in food that is eaten

Experiment 4.7 Testing for protein eye protection Add o few drops of copper sulphote solution to some protein solution in o test-fube. Now corelully odd o few drops of sodium hydroxide solution. Toke greot cofe os sodium hydroxide solution is corrosive.

A

Did the protein go purple

?

43

)

Corbohydrotes

Corbohydrotes ore mode up of the elements corbon (C), hydrogen (H) ond oxygen (O). Sugors ore corbohydrotes.

Did you know thot there ore different kinds of sugors ? The kind of sugor you put in your teo is colled sucrose. The kind of sugor thot is in milk is colled loctose. The sugor thot our bodies use most is glucose. Some foods rich in carbohydrates

We need corbohydrotes to give us energy. Sugors ore the fuelthot our bodies need.

Experiment

4.2

Tbsting

t'or glucose

Pour some glucose solution into o test-tube

A

eye protection

ffiA

Add q few drops of Benedict's solution. (Be coreful, this is hormful.) Corefully heot the test-tube in o woter both

Did the glucose turn oronge

?

Stqrch is olso o corbohydrote. You olreody know thot storch is o lorge molecule. It is mode up of lots of smoller glucose molecules

digestion

+>

joined together.

Experiment

4.3

small glucose molecules

large starch molecule

Whot do you moke when you digest storch Tbsting

for

starch

Holf fill o test-tube with storch solution.

?

A

eye protection

Add two drops of iodine solution.

\

Does the storch turn blue-block?

t Plonts often turn their glucose into storch to store it.

Glycogen is o lorge corbohydrote molecule like storch. Glycogen is olso mode up of glucose molecules joined together We store glycogen in our liver ond muscles. Our bodies chonge glycogen to glucose when we need it. Mony cheoper foods contoin q lot of corbohydrotes. Do you think foods contoining o lot of protein would be more or less expensive ?

4

ta o o3 o o

)

Fots

fatty acid molecule

Fots ore mode up of the elements corbon, hydrogen ond oxygen There ore mony different kinds of fots. Fots ore mode up of three fotty ocids joined together. There ore different kinds of fotty ocids. Do you think thot different fots hove different kinds of fotty ocids in them ?

glycerol molecule

A molecule of fat

Fots olso give us energy. Fots octuolly contoin more energy thon corbohydrotes. Our bodies use fots os on energy store. We store fots under the skin ond oround the heort ond kidneys.

When we ore short of energy our body uses the fot. Whot do you think hoppens if we eot too much fqt?

Experiment4.4

Tbsting for

fat

Put four drops of cooking oil into o test.tube.

A

ethanol is highly flammable

\

oil\

4,,

Add2 cm3 of ethonolto the oilond shoke the test-tube

pour into water

Add 2 cm3 of woter to the test-tube ond shoke ogoin.

shake again

shake

Does the oil turn cloudy white ? Fots ore good insulotors. They cut down heot loss Which onimols hove o lot of fot under the skin ? Fqts olso give buoyoncy. Why do wholes hove o thick loyer of blubber?

We

need: protelns for growth and reparr of cells carbohydrates lor enerry fats as a store of energy and lor warmth

Why con fot be bod for us? There ore two moin types of fot:

soturoted fot thot comes from onimols ond unsoturoted fot thot comes from plonts. Soturoted fots increose the level of cholesterol in our blood

Some foods rich in fat

Cholesterol is o chemicolmode in the liver ond found in the blood. The omount of cholesterol thot we produce depends upon our diet, but olso inherited foctors. High levels of cholesterol ore linked to on increosed risk of heort diseose ond on increose in blood pressure due to o norrowing of the blood vessels (see poge 85). Mono-unsoturoted fots hove little effect on blood cholesterol. Poly-unsoturoted fots moy help to reduce cholesterol levels.

Whot would your odvice be to reduce heort diseose

?

clean shiny inner surface

thick layer of fatty deposit

How a fatty deposit can narrow an artery

45

Our food gives us our energy. We need energy for oll the octivities thot we do. Corbohydrotes ond fots ore high-energy foods.

kilojoules (kJ), 1000ioules.

Energy in food is meosured in

where

I kilojoule =

cup of tea with milk sausage 150 kJ

500 kJ

bread and butter

600 kJ

fried egg

650 kJ

Look of these two meols: chips 1000 kJ

Which meol hos the highest energy content ? By how much? Which meol is the most heolthy ? How could you reduce the energy content in the first meol?

Meosuring the energy in food We con meosure the omount of energy in some food by burning it. As the food burns, it gives out energy. We con use this energy to heot up some wqter. The hotter the woter gets the more energy is in the food.

200 kJ

fresh fruit

juice 150 kJ

20 kJ

Weight of peanut (g)

Energy (joules)

:

2O

x 4.2

x

content

Temp. of water at

A

Temp. of water at end ('C)

Temp.

rise of water ('C)

eye protection peanut allergy

stand

temperoture rise of woter

Work out the energy content per grom (g) of peonut using this equotion: 0oules/g)

300 kJ

yoghurt 45 kJ

start ('C)

Work out how mony joules of energy were given out by your peonut using this equotion:

Energy

curried chicken

salad

4.5

Measuring the energy in a peanut Copy the results toble. Use o meosuring cylinder to pour out exoctly 20cm3 of woter into q boiling-tube. Tqke the temperoture of the wqter ond write it down in your toble. Weigh o peonut ond write down the weight in your toble. Put the peonut on the end of o mounted needle. Set the peonut olight ond hold it under the boiling-tube of wqter. When the peonut hqs burnt out, toke the temperofure of the woter ogoin. Write your result in your toble. Experiment

brown rice

boiling-tube

thermometer

energy given out by your peqnut (J) weight of your peonut (g)

mounted

Rother thon use such lorge numbers, you c olcohol

-|

corbon dioxide

Con you think of ony uses for fermentotion

+

energy

?

Yeost is used in wine-moking ond brewing (see poge 351). Yeast cells

Experiment 5.72 Fermentation Moke o mixture of yeost ond 10 7" glucose solution. Set the opporotus up os shown: Add o few drops of diqzine green indicotor. This turns pink in the obsence of oxygen. liquid

o Why did the hydrogencorbonote indicotor turn yellow ? o How long did this toke ? o Whot gos did the poroffin prevent from entering? o How did the diozine green prove thot no oxygen hqd entered

glucose ?

solution and yeast

hydrogencarbonate indicator

Plon on investigotion to find out whot offects the rote of fermentotion. Fermentotion not only puts the fizz into our drinks, it olso mokes our breod rise. Yeost contoins enzymes thot ferment the sugor in flour

Experiment 5.1.3 Moking dough rise Mix 209 flour ond 1. g sugor in o beoker. Add 20 cm3 of yeost mixture ond stir it to o poste. Pour the mixture into o meosuring cylinder. Record the volume of the dough every 3 minutes for 30 minutes. Drqw o line groph to show your results.

o Whot do you think mode your dough rise ? o Describe how your dough rose over the 30 minutes. Plon on investigotion to find out how you could moke your dough rise foster.

73

)

Muscles without oxygen

Your muscles need oxygen ond glucose to respire oerobicolly. These ore brought to your muscles by your blood system.

During long periods of vigorous octivity your muscles become fotigued ond they stop controcting efficiently. When this hoppens, your heort ond lungs con not get enough oxygen to your muscles quickly enough. This couses your muscles to stort to corry out onoerobic respirotion. Glucose is broken down to lqctic ocid. when there is no oxygen glucose ---------i> loctic

ocid

+

energy

Loctic ocid con slowly poison your muscles. This couses cromp. We must get rid of the loctic ocid. Hove you noticed thot we corry on breothing foster ond deeper ofter vigorous exercise ? The extro oxygen breoks down the loctic ocid. This extro oxygen is colled the oxygen debt. Our oxygen debt builds up ofter we exercise hord. It hos to be 'poid bock' stroight owoy. Sprinters build up loctic ocid in their muscles. They often hold their breoth during o 100 metre roce. Afterwords they need obout 7 litres of oxygen to get rid of the loctic ocid. They breothe deeply ofter the roce in order to repoy their oxygen debt. Long-distonce runners could not stond such o build up of loctic ocid. They run of o much slower speed. They build up some loctic ocid in the eorly stoges of the roce, but get rid of this while they ore running.

Anoerobic respirotion produces less energy thon oerobic respirotion. Without oxygen, glucose is only portly broken down into olcohol or loctic ocid. A lot of energy remoins in the molecules of olcohol ond loctic ocid. Energy released (kJ/g glucose) aerobic respiration fermentation by yeast anaerobic respiration in muscle

74

16.1

1.2

0.8

'l wanna repay my oxygen debt'

)

Biology ot work : Tioining ot oltitude In the 1968 Olympics, othletes who usuolly troined ond competed of seo level did not perform os well os expected. This wos becouse the gomes were held in Mexico City ot

on oltitude of.2242m. The othletes who normolly lived ot o high oltitude did well, porticulorly in the enduronce roces such os the 10 000 m.

At high oltitudes there is less oxygen in the oir. This meons thot less oxygen con be corried to the muscles by the blood. The body responds by : o releosing red blood cells stored in the spleen o increqsing the rote of which red blood cells ore mode o moking it eosier for hoemoglobin to give up its oxygen when it reoches the muscle tissue (see poge 88). The omount of hoemoglobin circuloting in the blood increoses by 50-90 %. This meons thot the blood is oble to corry more oxygen At oltitudes of 2OOO-2500 m, it tokes obout 2 weeks for the body to bring obout these chonges. Recent developments hove ottempted to reproduce the benefits of oltitude troining ot seo level. These include the use of hypoxic troining rooms, which hove the following benefits:

o reduction in trovelcosts o no chonge in oir pressure o no exposure to higher levels of ozone ond UV light o better oxygen supply to the tissues o drop in heort-beot rote.

A hypoxic training room high

Look of the groph,it shows how the number of red blood cells increosed in Himoloyon mountoin climbers during on expedition losting 110 doys. Why is it on odvontoge to the climbers to increose the number of their red blood cells? How long did it toke for the red blood cells to reoch their highest concentrotion ? Why do you think thot there wos no increose in the concentrotion of red blood cells between 4000 m ond 6000 m?

low 100 110 120 time (days)

75

Summory r Respirotion involves the breokdown of

o Exchonge of goses tokes ploce in the olveoli. o Your intercostolmuscles ond diophrqgm ore

glucose to releose energg.

used in breothing.

o Aerobic respirotion uses oxygen to do this. o Corbon dioxide is mode os o woste product

o Your breothing

rote is controlled by your broin ond increoses with exercise.

ond must be removed.

o

o Yeqst ond muscles ore qble to respire

The rote of respirotion con be meosured with q respirometer.

o Air entering your lungs is wormed,

without oxygen.

o Anqerobic respirotion

in muscle results in on oxygen debt thot hos to be repoid to oxidise loctic ocid to cqrbon dioxide qnd woter.

cleoned

ond moistened.

)

3.

Questions

1. Copy ond complete: Respirotion tokes ploce in ollour .... . The fuel . . . . . It is broken down to releose . . . . . Also produced ore woter ond the woste gos . . . When it tokes ploce in the presence of .... we coll it .... respirotion. These reoctions toke ploce in every living cell, inside tiny strucfures colled ... . .

for respirotion is

2. Look

ot the opporofus used in this experiment

:

Give on explonotion for eoch of the following o) When you breothe on o cold window, woter droplets form. b) Breothed-out oir turns lime woter cloudy quicker thon breothed-in oir. c) Alveoli (oir socs) ore very thin ond hove o lorge surfoce oreo. d) Plonts give out corbon dioxide in the dork, but toke it up in the light.

4. Look ot the diogrom of the respirometer drop of coloured liquid

spring clip

woodlice blowfly maggots

soda lime absorbs lime water

A

B

o) Suggest o title for the experiment. b)After 12 hours the tubes were exomined Whot results would you expect ? c) Whot wos tube B for? d)Whot would hove hoppened if the lime

woter hod been reploced by hydrocorbonote indicotor ?

76

carbon dioxide

wrre gauze

o) In which direction will the drop of coloured liquid move ? b) Whot mokes this hoppen ? c) Why must the spring clip be closed ot the stort of the experiment ? d) You ore given identicql sets of this opporotus. How could you investigote the effects of temperoture on the rote of respirotion of the moggots ?

5.

7.

The diogrom shows the humon breothing A

C

Write down o function for eoch of the

following: o) the C-shoped rings of cortiloge in the trocheo b)the epiglottis c) the pleurolmembrone d)the mucus in the trocheo e) the diophrogm.

system:

E

F

8.

The opporotus wos set up os shown thermometer

G

o) Write out letters A to G with the correct lobels. b) Motch ports A to G with these descriptions i) sheet of muscle forming the floor of the chest ii) one of these enters eoch lung iii) contoins the vocol cords

paraffin oil lime glucose and yeast solution

iv)

The flosk wos kept ot 35'C. After 15 minutes the lime woter hod turned cloudy. o) Whot gos wos given off ? b) Whot process produced the gos ? c) Why wos the flosk kept ot o constqnt 35 "C? d) Whot wqs the poroffin oil for ? e) Suggest o controlfor this experiment.

flexible tube kept open by rings of cortiloge v) where exchonge of goses tokes ploce vi) o slippery membrone vii) mode of spongy tissue ond found in the chest.

6.

The diogrom shows some olveoli (oir socs) ond o blood copillory in the lung. A alveoli

9.

The toble shows the units of loctic ocid produced in the leg muscles of on othlete. Time (minutes)

01020304050607080

Lactic acid units

0 1 712 I 6 3 1

B

blood capillary

C

D

o) Which orrow shows:

i) ii)

blood high in oxygen blood low in oxygen iii) the diffusion of oxygen iv) the diffusion of corbon dioxide ? b) Give two feotures of the olveoli thot help

water

1

o) Drow o line-groph using the doto. b)When did the loctic ocid reoch q moximum? Try to exploin this. c) Whot hoppened to the loctic ocid ofter this time

?

Try to exploin this.

Further questions on poge 171.

gos exchonge.

77

B[.O,OD qnd CI RCULATI ON

chapter 6

Your blood is corried oround your body in tubes colled

blood vessels. Your heort ond blood vessels moke up your blood system. Your blood circulotes round ond round your body in your

blood vessels. So the blood system is often colled the circulotory system Whot sort of things need to be corried round your body ? Your blood system tronsports some useful things like: o oxygen from your lungs to your cells o food from your gut to your cells.

It olso hos to remove woste chemicols like: o corbon dioxide from your cells to your lungs o woste chemicols from your liver to your kidneys. Your blood system olso tronsports chemicols like hormones, ontibodies ond blood proteins to oll the cells of your body.

A problem of size Mony smoll onimols do not need o blood system. Microscopic orgonisms like Amoebo con get things such os oxygen just by diffusion. They hove o lorge surfoce oreo compored to their volume. It is eosy for things to diffuse in ond out.

Amoeba

Even lorger invertebrotes like flotworms do not hove blood vessels. Their bodies ore so flot thot it is not for for goses ond liquids to diffuse in ond out. So why do we need o tronsport system

?

Lorger onimols con not just rely upon diffusion. Our bodies ore too lorge for moteriols to simply diffuse in ond out. It would toke o molecule of oxygen doys to diffuse from the outside to the centre of your broin We hove o system of tubes ond o pump to corry substonces oround our bodies quickly. !

78

A flatworm

qq

q q q

q qq

tq o.

q o,

)

Your circulotion

At the centre of your blood system is your heort. Its job is to pump the blood oround your body. The rest of the blood system is mode up of tubes colled blood vessels. There ore two moin types. Con you remember whot they ore colled ?

veins carry blood from the capillaries back to the heart

Arteries corry blood owoy from the heort. Veins corry blood bock to the heort.

arteries carry blood from the heart to the capillaries

veins have valves to keep blood flowing in the right direction

capillaries go to every cell in the body

When they get to on orgon in your body, orteries

bronch mony times. The smollest bronches ore colled copillories. The copillories then join up to form veins. It is in the copillories thot chemicols like oxygen, food ond corbon dioxide poss into ond out of the blood capillaries join up to make veins

The circulotory system is like o one-woy street. Blood con only go in one direction.

Whot hoppens of copillories

ar.teries split up to make capillaries

?

The orteries brqnch mony times untilthe smollest bronches form copillories. These crre very norrow ond toper os they reoch the body cells. Here o red blood cell con only just squeeze through.

Red blood cells inside a capillary

Blood flows through copillories very slowly, so this gives time for exchonge of moteriols to toke ploce. Copillory wolls ore only one cellthick. Oxygen ond food con eosily poss out of the copillory to the cells. Corbon dioxide ond other woste chemicols con eosily poss from the cells into the copillory. It is estimoted thot there ore over 80 000 km of these tiny tubes in your body. Thot's o huge surfoce oreo for things to poss ocross

!

Scanning electron micrograph of red blood cells entering a capillary

79

>

A double circulotion

Your heort is divided into two hqlves : the right ond the lelt. The blood in the right side does not mix with the blood in the left side.

So your circulotion is reolly in two ports:

o

The right side of your heort pumps blood to your lungs ond then bock to the heort ogoin. How does the blood chonge when it gets to your lungs ? Whot does it pick up ? Whot does it drop off ? In your lungs the blood picks up oxygen. We soy thot it becomes oxygenoted. The blood olso gets rid of corbon dioxide.

o

The left side of your heort pumps blood to the rest of your body ond then bock to the heort ogoin. How does the blood chonge when it gets to your body cells Whot does it drop off ? Whot does it pick up ?

? the heart

The blood gives up its oxygen to your body cells. We soy thot it becomes deoxygenoted. Corbon dioxide posses into the blood from the body cells.

Look ot the diogrom How mony times does the blood poss through the heort on one circuit of the body ? Thot's why it's colled o double circulotion.

W

Williom Horvey

wos on English physicion. He used his knowledge of onotomy to moke o unique discovery obout the circulotion of blood oround the body. As o result of coreful observotion ond corrying out experiments, he wos oble to exploin how blood moves oround the body in o circle - trovelling from the left side of the heort in orteries ond then bock to the right side of the heort in veins.

ln \623, he published his book On the Motions of the Heart and Blood.ln it he showed how the evidence from his experiments disproved mony of the long-held ideos of

I

iei*ai l4-isu idffiir

\ t

t

t't

il ;

s

iE:;,)

)'-'-'-

,

../

t4

the time.

Horvey olso predicted thot there were thousonds of tiny copillories connecting orteries to veins, despite being unoble to see them. Why wos Horvey unoble to observe blood copillories?

80

Harvey demonstrating the action of valves to a group of physicians in London

)

Arteries

An artery

When your heort muscles controct they force the blood into your orteries. Whot do you think the pressure of blood is like in the orteries ? Eoch beot of the heort pumps the blood olong under high pressure.

thick outer wall

The ortery wolls ore elostic ond stretch to toke the blood. Then they controct ond bounce bock to force the blood olong. This bouncing bock con be felt os o'pulse' os the blood flows through.

thick layer ol muscle and elastic fibres

Experiment 6.7 Taking your pulse Con you feel your pulse ? Try to feel on ortery ot your wrist or of the side of your neck. The number of pulses per minute shows how fost your heort is beoting.

How does your pulse rote compore with other people's Whot hoppens to your pulse rote when you exercise Plon on investigotion into the effect of vorious types of exercise on pulse rote.

?

?

A vein

)

two outer layers are thinner than arteries

Veins

Copillories join up to eventuolly form veins. Veins ore wider thon orteries ond hove thinner wolls. The pressure inside veins is much lower. So the blood flows much more slowly in them. The blood is often squeezed olong by your muscles.

The flow of blood in veins is helped by volves. Volves ore like double doors thot will only open in one direction. If you try to go bock in the other direction the doors won't open. Volves stop your blood from flowing bockwords.

outer wall

large space through which blood flows muscle and elastic fibres

( Valves open to let the

blood flow towards the heart

ffi

Valves close to stop

blood flowing backwards

81

)

Your heort

Your heort is neorly ollmuscle. It hos o big job to do. It is the pump thot circulotes blood oround your body. Your heort beots obout 70 times per minute - for o lifetime So it is just os well thot your heort muscle never tires.

The double pump Your heort is reolly two pumps side by side. The right side of your heort is one pump. The left side of your heort is onother pump. Eoch side is kept completely seporote. This woy the deoxygenoted blood on the right side does not mix with the oxygenoted blood on the left side.

On eoch side of the heort there ore two chombers

to body

The upper chombers ore colled qtrio (singulor otrium). Blood empties into them from veins. When the otrio controct they pump blood in to the lower chombers.

from body

to lungs

The lower chombers ore colled ventricles. These hove much more musculor wolls. When the ventricles controct they pump the blood out into orteries.

from lungs

left atrium

Between eoch otrium ond ventricle is o volve. Whot do you think thot it is for? The volve prevents the blood flowing bock into the otrium when the ventricle controcts.

Why do you think thot the ventricles hove more musculor wolls thon the otrio? Do they hove to pump the blood the some distonce Why not? The left ventricle hos o more musculor woll thon the right ventricle. Does it hove to pump the blood much further?

82

right atrium

valve

valve

?

right ventricle

left ventricle

The arrows show how the blood moves through the heart

)

Heort oction

The heort pumps blood when its muscle controcts When the muscle controcts the chomber gets smoller ond squeezes the blood out.

After eoch chomber controcts it reloxes. So it fills up with blood ogoin.

In perfect hormony The two sides of the heort work together. The otrio controct ond relox of the some time. The ventricles controct ond relox of the some time

from body

from lungs

heart

diastole

Diqstole

is when the heort muscles ore reloxed. Blood flows into the otrio from the veins.

Systole

o

o

is when the heort muscles controct

First the otrio controct ond force the blood into the ventricles. The volves between the otrio ond ventricles open due to the pressure of blood ogoinst them

Then the ventricles controct. They force the blood out into the orteries The volves close to prevent blood from flowing bock into the otrio.

filling right

atrium

right ventricle

to lungs

left atrium

to body

left ventricle

heart full

heart

systole

of blood

pumping

The right ventricle pumps blood to the lungs in the pulmonory ortery. pulmonary vein

left ventricle pumps blood to the rest of the body in the oorto (moin ortery). The

Deoxygenoted blood returns to the in the veno covo (moin vein). Oxygenoted blood returns to the in the pulmonory vein.

cava

right otrium

left otrium

pulmonary artery

aorta

83

)

{hrob, throb, throb.

Control of heortbeot

If the heort wos removed from the body it would continue to beot ! Whot does this tell you obout whot mokes the heort beot

?

The beoting of the heort is controlled by the pocemoker. This is o group of cells in the right otrium. The pocemoker sends electricol messoges to the

heort muscle.

'0{

These messoges stimulote the heort muscle to controct.

The pocemoker olso receives informotion from the broin. Some nerves slow down the heort rote, others speed it up. So the broin is oble to odjust the heort rote to the needs of the body.

Whot might couse your heort to beot foster

?

During exercise your muscles need more energy from respirotion in order to controct. So your heort beots foster ond the orteries supplying the muscles dilote (widen). These chonges increose the blood flow to the muscles

ond so:

o o

increose the supply of glucose ond oxygen increose the removol of corbon dioxide

The heort's blood supply

Regular exercise makes for a healthy heart

Despite being full of blood, the heort needs o blood supply of its own.

Coronory orteries corry oxygenoted blood to the heort muscle.

Why does the heort muscle need o good oxygen supply

?

Whqt else does it need from the blood to give energg? The heort muscle needs energy from respirotion in order to controct. Respirotion requires glucose ond oxygen. The coronory orteries supplies the heort muscle with both glucose ond oxygen.

Angiogram of the coronary arteries

u

Whot might hoppen if o coronory ortery become blocked

injuries, road accidents, poisonings

?

The oxygen supply to the heort muscle would be cut off. This could couse o coronory heort ottock. If the heort muscle is storved of oxygen then it will die. If the domoge to the heort muscle is extensive, then the person

diseases of

44Yo

the lungs and respiratory system

77o 11o/o

moy die. all other causes

However, mony people survive heort ottocks, with treotment followed by odjustment to their lifestyles.

Heort diseose

couses o quorter of oll deoths in Britoin. It is the biggest single killer of middle-oged men in the developed world.

diseases of the heart and blood vessels

33/"

Causes of death in people under 75 in the UK (total deaths: 267 500)

Slowing the flow Heolthy orteries hove o smooth lining. They let the blood flow through eosily. A chemicol colled cholesterol, mode in the liver ond found in the diet, con stick to the wolls. This con norrow the ortery ond slow down the flow of blood. 1 Fatty deposits break away from artery wall

2 Fatty deposit blocks the artery

blood flow

3 Blood flow along the artery stops

The ortery wolls con become rough. This con couse the blood to clot ond block the vessel. The blockoge is colled o thrombosis.

Norrowing of the coronory ortery couses serious problems : o If the coronory ortery gets portly blocked it con couse chest poins, especiolly if octivity or emotion mokes the heort work horder. This is colled ongino. It is coused by not enough oxygen getting to the heort muscle. Angino should oct os o worning to the sufferer.

o

A totolblockoge or thrombosis cqn couse o heort ottock. The supply of oxygen is cut off. It couses o severe poin in the chest. The offected port of the heort is domoged.

The heort moy stop beoting oltogether - this is colled cordioc orrest. Deoth willfollow unless the heort storts beqting ogoin within minutes.

A blocked artery in sectton

85

Risk foctors Risk foctors ore things thot ore thought to increose the chonces of getting heort diseose.

Some of them you con't ovoid like: o Inherited genes - heort diseose tends to run in fomilies. o Age - the chonces of getting heort diseose increose with oge o Sex - men ore more likely to get heort diseose thon women. Some of the other risk foctors you con do something obout ore o Eating Jatty foods - these con increose cholesterol in the blood.

o Being ooer-weight. o Smoking. o Taking little or no exercise. Avoiding heort diseose o Take care of your diet:

-

Eot more poultry ond fish - they ore less fotty Cut down on fried foods. Eot less red meot. Eot more fresh fruit ond vegetobles.

o Take some regular exercise. o Do not smoke. Stotins ore heort drugs thot were invented20 yeors ogo. They hove been proved to cut deoth rotes from heort diseose by 28 per cent ond further non-fotol heort ottocks by 31 per cent. Their development hos been hindered by two serious side effects irritotion of the liver ond domoge to muscle cells. Both ore rore. Experiment 6.2 Dissecting a sheep's heart Look of o dissected sheep's heqrt. (The heort is cut open by two verticol cuts, one through the left otrium qnd ventricle, the other through the right otrium ond ventricle.) Notice the differences in the thickness of the wolls.

aorta

pulmonary artery

vena cava pulmonary vein

If the blood vessels ore still intoct, try to find out which is which.

Look for the coronory vessels on the surfoce. Look inside for: o the volves between the otrio ond the ventricles, o the volves of the bose of the pulmonory ortery qnd oorto. Try running o streom of woter ogoinst the vqlves. Do they open ? How does this help the heort ? Wosh your honds with soop ond woter when you hove finished.

86

right atrium

right ventricle

atrium

ventricle

)

Your blood

If someone hos on occident or o mojor operotion, they often lose o lot of blood. The blood is vitolfor life. It hos to be reploced quickly. The person hos to hove o blood trqnsfusion. (For more obout blood tronsfusions see Biology ot Work, poge 93.) So why is your blood so importont to you

?

Your blood does two importont things:

o o

it tronsports things from one port of your body to onother.

it helps to protect your body from diseose.

Whot's blood mode of ? You hove obout 5 litres of blood in your body. Thot's o bucket full. Blood looks like o red liquid, but there's more to it thon thot

Whot hoppens if you leove o somple of blood to stond

?

Con you see it hos seporoted into two ports

o

?_:

l__o

a

**l-q

r'9,

Look ot the test-tubes: ?

The yellow liquid is colled plosmo. It is moinly woter with chemicols dissolved in it. Some of these ore :

-

Food, such os sugors, omino ocids, vitomins ond minerols.

rt'

Chemicolwoste like ureo. Blood proteins like ontibodies. Hormones

-

I d

L.

chemicols thot controlthings like our growth.

o At the bottom

of the test-tube the cells hove settled out.

There ore three moin types of blood cells

-

:

blood is made up of

Red cells hove no nucleus. They look red becouse they hove o red pigment

,

colled hoemoglobin.

-

-

White cells do hove o nucleus. There ore two moin types: lymphocytes ond phogocytes. White cells do not hove hoemoglobin so they don't look red.

Plotelets ore tiny bits of cells.

+

(|l t$

red cells

rrvhite

cells

platelets

floating in a yellow watery liquid called plasma

87

)

Red cells

There ore obout o million red cells in eoch drop of blood. They ore mode in the bone morrow. Red cells corry oxygen. How does their shope help them to do this

?

Red cells ore disc-shoped with the middle pushed in. They hove o lorge surfoce oreo to volume rotio. This helps them to obsorb o lot of oxygen. red blood cell

Red cells hove no nucleus.

Insteod the cell is filled with hoemoglobin. This is o speciolprotein thot contoins iron. You must hove enough iron in your diet to moke enough hoemoglobin for your red cells.

Hoemoglobin combines eosily with oxygen. It forms oxyhoemoglobin.

Hoemoglobin

*

cellmembrane haemoglobin

oxygen--------> oxyhoemoglobin

Look ot the diogrom: Where does oxyhoemoglobin form ? Where does oxyhoemoglobin breok down to give oxygen ond hoemoglobin ?

molecules of oxygen

6.3

Demonstration Tiansporting goses in the blood Your teocher will give you some blood thot is sofe to use. Pour equol omounts into two boiling-fubes A ond B. Bubble oxygen through tube A ond corbon dioxide through tube B.

o Why does the blood in A go bright red ? o Does the blood in tube B hove less oxygen

?

Now try bubbling oxygen through the blood in tube B ond corbon dioxide through the blood in tube A. Try to exploin your observotions. Wosh your honds with soop qnd woter when you hove finished.

an alveolus in the lung

1 Oxygen diffuses from the alveoli

into the blood. The oxygen 'sticks'to the haemoglobin in the red cells making

4 The empty red blood cells return to the lungs to pick up more oxygen.

2 The red blood

cells carry the oxygen to the cells which need it. -

/ 3 The oxygen becomes'unstuck'

CO2 too

from the oxyhaemoglobin and diffuses out of the blood to the cells. The oxyhaemoglobin is now lust haemoglobin again.

!

The red cells olso corry some corbon dioxide. But most of it is corried dissolved in the plosmo. Where do you think corbon dioxide enters the blood Where do you think corbon dioxide leaues the blood

88

? ?

red blood cells

>

White cells

v&

The white cells fight diseose. There ore for fewer of them thon red cells. They olso look different. Con you see how they ore different ?

White cells ore not disc-shoped. They do not hove hoemoglobin. They do hove o nucleus. Like red cells, the white cells ore mode in the bone morrow. Their job is to protect the body from ony pothogens thot get into the blood. The two types of white cells do this in different woys.

Oo'o

l

a a

a a

Lymphocytes When o bocterium or virus enters the body the white cells recognise thot it is 'foreign' ond should not be there. The lymphocytes moke chemicols colled ontibodies. These ottock the pothogens in o number of woys : o They moke them stick together. o They dissolve them. o They destroy the toxins (poisons) thot the pothogens moke.

o

a

f

t a

aa

aa O

a

.tr t'

t

a

a a

]

beingD destroyed byE antibodies 3

r tjrl'o

r

*.*f

After you hove hod o diseose the ontibodies stoy in your blood. They moke you immune to the diseose. There is o different ontibody for eoch type of pothogen. You con leorn more obout immunity in Chopter 10.

Phogocytes These ore the 'cell-eoters'. They engulf or swollow up pothogens ond toke them into the cell. They then digest them ond kill them.

When pothogens invode the body white cells move towords them They con squeeze through copillory wolls.

)

bacteria being engulfed

Experiment 6.4 Making a blood smear Your teocher willgive you some blood thqt is sofe to use Put o few drops on one end of o microscope slide. Use onother slide to drow the blood over the surfqce. This gives q blood smeor.

When it is dry put o few drops of Leishmqn's stoin on the smeor. After 5 minutes wqsh the stqin off. When it is dry, look qt your slide under the microscope. Identify qnd drow ony white blood cells. When you hove finished, dispose of your slide into o beoker of disinfectqnt.

89

)

Blood clotting

When you cut yourself you bleed. Before long the blood thickens ond the bleeding stops. The thickened blood hos formed o clot. This is onother woy thot the blood fights diseose. Without clotting, blood would be lost ond pothogens would get in.

threads of fibrin

1 The skin is cut and blood starts

leaking out of the body.

-> scab

2 There is a protein in the blood called fibrinogen. When platelets come in

contact with air they turn the fibrinogen into threads of fibrin. The threads make a net over the cut.

AIDS (Acquired immune deficiency syndrome)

Most people hove heord of AIDS. But how mony know exoctly whot it is ? AIDS is octuolly o collection of diseoses which result from o weqkening of the

immune system. AIDS is coused by o virus colled HIV. HIV (humon immunodeficiency virus) ottocks ond destroys the white blood cells thot help us to fight infection. This reduces the body's obility to fight diseose

A white blood cell infected by the HIV virus (shown in red)

The eorly symptoms of AIDS ore very much like flu, with swollen glonds ond o high temperoture. Loter symptoms might include weight loss, vorious types of concer ond o decreose in broin function. Cotching HIV does not necessorily result in AIDS. Some people simply remoin os corriers, with no symptoms of

How is HIV tronsmitted

i

,.

,

,''/

ol1.

?

HIV is trqnsmitted in the blood or semen. The virus con pqss from one person to onother during sexuol intercourse. Either portner moy infect the other. The virus con olso be possed vio hypodermic needles contominoted with infected blood. In this woy, HIV hos spreod very quickly omongst drug oddicts

The HIV virus can be passed via

dirty needles

Unborn bobies qre olso ot risk from HIV. This is becouse the virus con poss ocross the plocento to the fetus.

How con AIDS be prevented? Although there is no cure for AIDS ond os yet no voccine for HIV there ore precoutions thot con reduce its spreod. These include o the use of condoms during sexuol intercourse o setting up free needle exchonges to reduce the use of shored needles omongst drug users o corefulscreening of donoted blood used for tronsfusions. :

A government leaflet warning about the dangers of AlDs

754

)

Biology ot work

:

Antibodies ond pregn(mcy testing

As we hqve seen eorlier in this chopter, ontibodies ploy on importont role in our immune system.

They olso hove o wide ronge of other uses, e.g. in pregnoncy testing ond the inoctivotion of poisons. To use ontibodies in this woy, scientists hove found q wqy of creoting pure somples

colled

monoclonol ontibodies.

How ore these monoclonolontibodies produced? Firstly, scientists toke lymphocyte B cells thot produce o specific ontibody. Then they combine them with o type of ropidly dividing tumour (concer) cell. These cells with fused nuclei ore colled

A commercial pregnancy testing kit

hybridomo cells. They undergo repeoted cell division to produce identicol hybridomos. Eoch hybridomo produces the specific ontibody originolly coded for by the B lymphocyte cell. In pregnoncy testing kits, these ontibodies con be used to detect the presence of o hormone colled humon chorionic gonodotrophin (hCG) This is found in the urine of women in the eorly stoges of pregnoncy. The test kit hos o dipstick, which hos o bond of the ontibodies on its surfoce. When this stick is dipped in o urine somple these ontibodies willbind with ony molecules of hCG

thqt ore present. This combinotion of hormone ond ontibody then moves up the stick. Eventuolly it reoches onother bond of ontibodies which olso bind to hCG, ond ot this point the combinotion of ontibodies ond hCG willshow up os o coloured line.

Test stick showing a positive result

If this line is seen on the dipstick then the test is positive, the womon is pregnont.

155

)

Biology of work: Preserving food Do you know whot mokes food go off

?

Bocteriq ond fungi get into the food from the oir. They ottock the food ond moke it toste bod. Some of these microbes con moke us ill. To stop food going bod we con preserve it. To do this we must:

o killthe microbes in the food, ond o stop them from growing ogoin.

Whot conditions do you think stops food from going bod ?

Fancy these grapes?

o Heoting

food to o high temperoture sterilises it. It con then be seoled in cleon cons or bottles.

o Pqsteurisotion

kills the bocterio in milk. It wos invented by Louis Posteur. The milk is heoted to 72"C for 15 seconds, then cooled quickly. This kills most of the bocterio ond does not offect the flovour.

o Cooling

food stops microbes from growing ond reproducing but it does not killthem.

A refrigerotor keeps food ot obout 5 "C. This willkeep food fresh for o few doys. A freezer preserves food of below - 18 'C. This stops oll microbe octivity ond food con be preserved for mony months. But once the food thows the microbes stort to grow ogoin. Frozen food should be fully defrosted before

it is thoroughly cooked, otherwise the microbes willjust be wormed by the cooking ond will multiply quickly. o6?j FReeze

156

)

Biology of work: Preserving food o Drying

is o woy of preserving foods like fruit, vegetobles ond some meots. The microbes con not live without woter. Some foods like coffee ond soups ore freeze-dried. The food is frozen ond the ice is drown off in o vocuum before seoling in pockets.

o Chemicols

con killmicrobes in food. Mony food odditives oct os preservotives, including sulfur dioxide, nitrotes ond nitrites. Eoch one is given on 'E number'.

Other chemicols thot hove been used

Freeze-dried foods

for mony yeors ore:

Pickling foods in vinegor mokes it too ocid for microbes to live.

Adding solt tokes woter out of the food by osmosis so the microbes die. The sugor in preserved joms olso mokes microbes lose woter by osmosis. Fish like kippers ond solmon ore preserved by smoking. The smoke kills the microbes in the foods.

o Irrodiotion

kills the bocterio ond fungi thot couse food spoiloge.

The food is exposed to gommo rodiotion. How are each of these foods preserved This kills the microbes but does not denoture enzymes in the food. So the ripening ond texture of fruit ond vegetobles is not offected. Food connot be sold for o period of 24 hours ofter irrqdiotion. In the post there hos been resistonce to this technique.

?

Think obout orguments for ond ogoinst food preservotion by

- irrodiotion - chemicol preservotives.

L57

Summory o

Pothogens ore microbes thot couse diseose. They include bocterio, fungi ond viruses.

o

o

The symptoms of q diseqse ore coused by the toxins mode by the pothogens.

o A voccine

o

Pothogens con be spreod in the oir, by

Good hygiene is the best woy of preventing the spreod of diseose.

o

Disinfectonts ond ontiseptics help to prevent the spreod of infection.

o

The body's own defences include skin, blood qnd mucus lining the oir possoges of the lungs.

) l.

Questions Copy ond complete: Pothogens ore . . . . thot couse diseose. Humon diseoses ore coused by . . . ., bocterio ond . . . . . The eorly stoge of odiseose is colled its . . . . period. The symptoms of o diseose ore coused by the . . . . mode by the pothogens. If something is microbe-free we soy thot it is . . . . . Pothogens ore killed on work surfoces by . . . . . Pothogens ore killed on living tissues by using . . . . . Your oir possoges hove cells thot moke . . . . . This trops dust ond . . . . ond tiny hoirs colled . . . . corry the mucus up to the throot.

2. Exploin why you should: o)Alwoys wosh your honds before hondling food. b) Never shore o towelwith someone. c) Alwoys wosh your honds ofter going to the toilet. d) Never let o dog lick your foce.

3.

o) Whot does it meon when you ore immune

to o diseose ? b) How is immunity brought obout? c) Whot is o voccine ? d) How does o voccine work?

158

is o deod or hormless somple of o

diseqse microbe.

o

Antibiotic drugs hqve been very successful in the treotment of diseose.

o

Clinicoltriols ore used to determine whether new drugs qnd treotments ore both sofe ond effective.

o

Tuberculosis, molorio qnd AIDS ore very different diseoses coused by very different pothogens ond spreod in different woys.

touch, in food ond woter, ond by qnimols.

o

When you cotch o diseqse your body mokes qntibodies thot give you immunity.

4.

The opporotus below wos used in on experiment to find out the conditions which couse milk to decoy.

x

z

Y

glass tu

glass

cotton wool

sterile milk

did go

milk heated to 66oC and then cooled

sterile milk

off

did not go

off

dld not go off

The milk in test-tubes X ond Y wos sterilised

by boiling. o) Whot kind of orgonisms moke food go bod ? b) Exploin why the milk in test-tube X went off but the milk in test-tube Y did not. c) Milk is often preserved by the treotment in test-tube Z. Why is it better to use this method rother thon boiling the milk?

5. Look

ot the groph. It shows o potient's temperoture when suffering from o bocteriol

8.

Some ontibiotics kill bocterio whereos others prevent the bocterio from dividing. Bocterio were grown in three tubes. Equivolent doses of different ontibiotics were odded to eqch tube. The number of living bocterio wos counted every hour for 10 hours. The following groph shows the results.

diseose. 41

I

o40

e-

I \,\

3ss 8_ E

s8

l i YV

I

(U

V

(!

I

q)

o (o

9^a 3l

c

c

=

3so (6

streptomycin

o.

o)

E I

I

0

I

5

I

I

0

l c

I

't5 days

20

25

o) Which ontibiotic killed the bocterio fostest ? b) Exploin your onswer to o). c) Which ontibiotic hod little, if ony, effect on the number of bocterio ? d) Exploin your onswer to c). e) Why ore ontibiotics useful even if they only stop bocterio dividing ?

o) Whot symptom of the diseose is shown on

the groph ? b) How long wos the incubotion period ? Whot wos hoppening during this time ? c) Whot coused the fever ond how long did it lost ?

9. o) Whot is on ontibiotic

The following groph shows the number of people in the UK who hove hod tuberculosis (TB) ond the number of sufferers who hove died from the diseose.

?

b) How wos the first ontibiotic discovered ? c) In the 1960s Americon soldiers in Metnom were treoted for syphilis with the ontibiotic penicillin. But some of the syphilis pothogens become resistont to the penicillin. How do you think this could hoppen ? Copy ond complete the following toble to show how the diseoses ore spreod.

50 o E c(! o f

40

-c

30

tetanus

how spread

TB sufie ers

.c 0)

20

deatt

E f

disease

036912 time in hours

tnt".tion

7.

penicillin

_o

35

6.

chloramphenicol

o)

c

lrom

10 0

1940

1950

cold/flu cholera tuberculosis plague

syphilis malaria athlete's foot

-

B

1960

1970

1980

1990

year

o) Suggest which yeor voccinotions ogoinst

TB begon.

b)From the groph determine: i) the number of sufferers in 1960 ii) the number of deoths in 1960 iii) colculote the percentoge of sufferers thot died in 1960.

Further questions on poge 171. 159

i+-

I s*)

a;

chapter 77

I

o

Aspirin, connobis, olcohol, porocetomol ond heroin These ore oll drugs. So whot exoctly is o drug?

A drug is o chemicol thot offects the woy in which your nervous system works. Drugs con be beneficiol or hormful. Mony medicines contoin useful drugs such os ontibiotics ond poinkillers.

Piriton Tablcb (drlorphcniraminc mehah 4mg)

Fagt r€lief,fro.n n€ttle rash, hirrec, heat nsh. prickly het or dematitis; reaclions to food, medicine or inseci bics; hayfu*r eympoms of the eyes and nose INGn:OISNIS Actiw: chlorphmiamire maleae. Alp contains: lacloee, maize iton oxide (El72) starch, magnesiuo stearate, olouc oosrcf AAfir rake one tablet qrcry 6ur to six hours (maximum 6 in ore dav). Oril&cn acd 6f 2: Half a ablei aary fouI to six hours (maximum 6 hals in one iiry). Not recotnm€rded fo drildran under 6 lf mDtoms oeEist consult rour douor rol DRUG$ vou rntrlxtNc Please ud the mloced information haflet carefrrlly befiorc use MEDICINES OUr OCrHE IE CII O[ CHlLDlIliI

pllo

[l

xi norrek nrnorrinrrs r IPAll

Medicines contoin of leost one drug. Thot's why you not eus€ madrinery. Awid alcoholic dtihk. should be very corefulwhen you use them. Some medicines ore only ovoiloble on prescription but p PLIO!,49/0106 PiriurisaGliloEdema*O1994 Glanopharmaca(elsUKu4U811 lBt,England con be dongerous if you exceed the prescribed dose. But there ore other drugs thot ore not useful. Some like tobocco ore legol, but others like connobis ond ecstosy ore not. Alcoholond tobocco ore the two commonest drugs. They ore eosily ovoiloble but con couse serious heolth problems. There ore mony different drugs ond solvents. Different drugs hove different effects on people. The strength of the drug olso offects whot it does to you

t

*16

o r!

Britoin hos strict lows ogoinst people who possess, sell or poss on certoin drugs. Breoking these lows con meon o fine, coution or moybe o prison sentence.

Closs A drugs include: cocoine, heroin, LSD, methodone, morphine, opium, ecstosy ond connobinol, except where it is contoined in connobis or connobis resin

I

TUT'S

160

DNUGS

lrGUls[!

Closs B drugs include omphetomine, codeine (in concentrotions obove 2.5"/"), Ritolin ond borbiturotes. Closs B drugs become closs A drugs if they ore prepored for injection. In Moy 2008, connobis wos reclossified from o closs C to o closs B drug Closs C drugs include mild omphetomines (like slimming pills), tronquillisers (e.g. Volium) ond onobolic steroids.

Sercbelo!.alole

I

Some people toke o drug without knowing whot's in it or how powerful it is. This mokes toking the drug even more dongerous.

In the UK drugs ore legolly clossified, closs A being the most dongerous with the heoviest penolties ond closs C being the leost dongerous with the lightest penolties.

m

"

)

How do drugs work

?

Drugs con be put into different cotegories occording to their generol effects :

o Stimulonts

ore drugs thot speed up the nervous system ond shorten o person's reoction time. They increose the speed of tronsmission of impulses ocross the synopse. Coffeine is o mild stimulont found in coffee, teo ond colo.

'' rf'\*"

t+1$

t

1

Amphetomines ond cocoine ore for more powerful stimulonts. Ecstosy toblets ore stimulonts thot some people toke to moke them feel os if they hqve more energy. Some young people hove died through toking ecstosy.

o

ffi

#

Wffi

Depressonts ore drugs thot slow down the nervous system ond lengthen reoction time. They oct by reducing the rote of which nerve impulses poss ocross the synopses. Depressonts (or sedotives) include borbiturotes ond

heroin. Benzodiozepines, Iike Temozepom, hove now reploced borbiturotes for most medicol purposes - they ore known os tronquillisers.

r

Pqinkillers

such os ospirin ond porocetomol con help to relieve poinful conditions such os heodoche, migroine,

I ;

neurolgio, influenzo ond rheumotic poin. Poinkillers oct by blocking nerve impulses of the Many medical drugs can be dangerous if taken synopse, os does morphine. in an uncontrolled way and are available only on prescription from a doctor. As with ony medicinol drug, it is very importont not to exceed the stoted dose of porocetomol. Immediote medicol help must be sort in the cose of on overdose, even lf o person feels well, becouse of the risk of deloyed, serious liver domoge.

o Performonce-enhoncing drugs such os onobolic steroids hove been used by othletes to build up muscle bulk. (See Biology ot work: The misuse of drugs in sport, poge 168.)

o Hollucinogens

ore o group of drugs thot con produce sensotions of folse identity ond distort whot is seen ond heord. As the nome suggests they induce hollucinotions. They include connobis ond the more powerful hollucinogen LSD (lysergic ocid diethylomide). LSD fuelled the psychedelic rock ond ort movements of the lote sixties. (See poge 356 for the importonce ond medicinolvolue of drugs produced by plonts.)

'

Disraeli Gears' by Cream

151

Drug obuse Some hord drugs con be extremely hormful ond con leod to severe heolth problems porticulorly to the body's nervous system, liver ond kidneys. Offences involving hord drugs, like heroin ond cocoine, ore obout

10% of olldrug offences. This con be compored with connobis (76%) ond omphetomines (72% of oll drug offences). Injecting o drug is the most dongerous woy of toking it. It is eosy to bverdose' ond shoring needles spreods hepotitis ond HIV the virus thot couses AIDS. The body gets used to some kinds of drugs. To get the some effect o person hos to toke on increosing omount of the drug. The body hos developed o tolerqnce to it. A person con become dependent on the drug if they stort to hove to toke it regulorly. Addiction meons thot the person hos become so dependent on the drug thqt it is doing them serious horm. If o person stops toking o drug they hove become oddicted to, they develop is not token these effects con fode

withdrowol symptoms. But if the drug ofter 2 or 3 weeks rehobilitotion.

Connobis ond opiotes Connobis is less oddictive thon tobocco ond olcohol, but smoking it moy couse psychologicol problems to develop. Heovy users cqn disploy oggressive behoviour if their supply suddenly stops A government report found thqt use of connobis is not ossocioted with mojor heolth or sociologicolproblems, but it moy be o'gotewoy' drug to more hormfulsubstonces, like heroin ond cocoine. Connobis hos o higher tqr content thon tobocco so smoking it presents the some risks of bronchitis, emphysemo ond lung concer. Confusion over the lows on connobis could increose if plons to reintroduce tougher lqws on stronger vorieties of the drug go oheod. 'Skunk weed' is o super-shength form of the drug ond is soid to be up to ten times shonger thon conventionol cqnnobis. Medicolreseorch hqs shown thot skunk connobis con trigger serious psychotic behoviour, such os hollucinotions qnd poronoid delusions.

Cannabis plants

: ':7;W

Connobis hos been widely known for its medicinol use in poin relief from o number of serious conditions : o concer: connobis con suppress nouseo brought on by chemotheropy o AIDS: it con increose oppetite ond reduce weight loss o gloucomo (on eye condition): it con relieve eye pressure o multiple sclerosis: it con qlleviote sposms, poin ond tremors.

Opiotes ore o group of drugs derived from opium in poppies. They include morphine which is often used os o poin-reducing drug for terminolly ill potients. 162

Queen Victoria was given cannabis to ease her period pains

)

Solvents

Solvents ore everydoy products like glues, dry-cleoning fluid, oerosols ond lighter fuel. They give off fumes thot sniffers breothe in. Solvents contqin dongerous chemicqls thot con killyou Solvent obuse is o growing problem omong youngsters aged12 to 16. It is ogoinst the low for shopkeepers to sell solvents to people under 18 yeors of oge. But mony of the solvents ore eosily ovoiloble oround the home. Solvent fumes ore obsorbed by the lungs ond soon get to the broin. They slow down breothing ond heortbeot rote. Repeoted or deep breothing con couse loss of

control ond unconsciousness. Solvents con couse domoge to the liveE lungs ond broin. Solvent obuse cloims more deoths thon heroin ond cocoine put together. Some people die immediotely ofter inholing some chemicqls like oerosols, cleoning fluids ond butone gos. These 'sudden sniff ' deoths ore often due to heort foilure.

Suffocotion con occur if sniffers inhole from lorge plostic bogs.

Aerosol sproys squirted into the mouth con fueeze the oir pqssoges cousing suffocotion. Sniffers con qppeor to be drunk. They run the risks linked with being drunk, like

o o

folling from o building or being involved in o rood occident, possing out ond choking on their own vomit

There is olso o risk of fire becouse mony solvents ore flommoble. The best odvice is neuer inhale solvents. Describe the hormful effects of solvents ond tobocco on the body ond the dongers of controcting HIV ond hepotitis when injecting drugs.

153

Y

)

Alcohol

Alcohol is o sociolly occeptoble drug. It is o port of mony people's sociol lives. Alcohol is mode when yeost is odded to o sugory solution such os grope juice. The yeost breoks down the sugor to moke qlcohol ond corbon dioxide gos. This is colled fermentotion.

Alcoholis o depressqnt-it slows down your body's reoctions. As with mony other drugs it con be obused. Alcohol does not often kill- o person usuolly loses consciousness before they con toke o fotol omount. Some people become dependent upon olcohol. Their bodies develop o toleronce ond they need to toke greoter omounts to get the some effect. People thot become oddicted to olcohol con not foce life without o drink They ore colled olcoholics.

Alcohol is obsorbed through the gut ond corried to the broin in the blood. From there it offects the nervous system. Mony people find o little olcoholreloxing. Increosing omounts moke them dizzy. Their judgement ond reoctions become offected. For this reoson o person should not drink ond drive. With greoter omounts of olcoholpeople lose control of their muscles ond their speech becomes slurred. A person in this stote is more likely to get into o fight or hove on occident. Their coordinotion becomes so poor thot they con not wolk ond end up possing out.

1 glass wine

Look ot the diogrom: How mony units of olcoholore there in - o double whisky - opint of beer? Different bronds of olcoholic drinks hove different strengths of olcohol. Why ore spirits served in smoller glosses thon beer? Some logers ore much stronger thon others. The strength of qlcohol is shown on the lobel os percentoge volume of olcohol.

l&

1/2 pint beer

1/2 pint cider (0.3 litre)

(0.3 litre) 1 glass sherry

1 single

whisky

All these drinks contain 1 unit of alcohol

Long-term effects of olcohol Drinking lorge omounts of olcohol over o number of yeors con hove serious effects on heolth. It con leod to stomoch ulcers, heort diseose ond broin domoge. The liver is the port of the body thot breoks down olcohol. Alcohol obuse over o number of yeors con leod to cirrhosis of the liver. The liver tissue becomes scorred ond its heolthy cells become reploced with fot, or fibrous tissue. The liver becomes less oble to corry out its job of removing the toxins from the blood. Even o heolthy liver tokes time to breok down olcoholond moke it hormless. It tokes obout one hour to remove one unit of olcoholfrom the blood. So depending upon the strength ond quontity of the drink, it moy toke severol hours before the body is free from olcohol.

10

=

-co oh :N

(E^

o-

_6 Oa E;

o-

96 Different drinks contoin different omounts of olcohol. Also o 'sofe' omount of olcohol will depend upon oge, sex, body size ond metobolic rote. The sofe omount for o womon is obout two-thirds of thot for o mon of the some weight.

Why do you think there ore legol limits for the level of olcohol in the blood ond breoth for drivers ond pilots ?

8

4

a7

=-

O.= E

2

2

46

I

10

units of alcohol

Like mony other drugs olcohol is hobit-forming. A sociol drinker con turn into o problem drinker.

Mony people who become dependent on olcohol do not think thot they ore. They try to convince themselves thot they do not hove o problem. They feel tense ond irritoble ond find it hord to cope with everydoy problems without o drink. Alcoholics con couse their fomilies poin ond misery. They con become oggressive ofter drinking ond spend o lot of money on drink. Orgonisotions like Alcoholics Anonymous con help olcoholics.

165

)

Smoking ond heolth

Smoking con domoge your heolth. It con couse diseoses of the lungs ond heort. It is estimoted thot every cigorette shortens o smoker's life by 14 minutes. Most heovy smokers die from diseoses coused by smoking.

Toxic chemicols Tobocco smoke contoins lots of chemicols. Mony of these qre hormful

{. {

t

:

Nicotine

is o drug. It octs upon the brqin ond nervous system. Smokers become oddicted to it. Thot's why they find it so hord to give up. Nicotine mokes the heort beot foster ond norrows the blood vessels. This con ccluse heort diseose ond high blood pressure.

Tor collects in the lungs when the smoke cools. It contoins over o thousond chemicols. Some of these con couse concer (ore corcinogenic). Tor olso irritotes your oir possoges ond mokes them norrower. It gives you'smoker's cough'.

Corbon monoxide is o poisonous

gos.

It is token up by the blood insteod of oxygen. So corbon monoxide stops the blood corrying os much oxygen os it should. If o womon smokes during pregnoncy there moy not be enough oxygen in the blood for the boby to develop properly. Due to this the boby moy hove o smoller birth weight ond is sometimes premoture. Porticulotes ore smoll burnt frogments of tobocco. They con occumulote in the lung tissue.

Diseoses coused by smoking Bronchitis is when the oir possoges become

inflomed. your possoges The cilio on the cells lining oir stop beoting. So the mucus, dirt ond bocterio stoy in your lungs. The bocterio stort to breed resulting in chronic bronchitis ond 'smoker's cough'. Lorge omounts of phlegm (o mixture of mucus, bqcterio ond white blood cells) ore produced, which the sufferer ottempts to cough up.

Emphysemo is when chemicqls in tobocco smoke weoken the wolls of the olveoli. Coughing con burst them domoging the lung tissue. Your lungs con not toke in enough oxygen ond you get breothless.

76

The tararxl dlscharge thatcolects h the lungs ol an averaBe srno*et

bronchiole alveolus (air sac)

rface area greatly

person suffering healthy person reduced lrom emphysema

Someone with emphysema can get very short of breath. Their alveoli have less surface area. So there is /ess gas exchange,

Heort diseose Nicotine ond corbon monoxide moke the blood clot more eosily. This con block the orteries to the heort especiolly if they olreody hove fot deposits lining them. Blocked orteries reduce the supply of oxygen to the heort ond this domoges the heort muscle. Lung concer Ninety percent of lung concer occurs in smokers. Tor is thought to be the moin couse. Tumours form in the lung ond if they ore not discovered quickly they con spreod round the body. Concers con olso originote in the mouth, throot ond oesophogus. Look ot the groph: It shows the number of deoths from lung diseose in Englond ond Woles from 1916-1960. Whot hos hoppened to the number of deoths from bronchitis ond tuberculosis over this time ? Con you exploin this ? Whot hos hoppened to the numbers of deoths from lung concer over this time ? Con you exploin this ? Demonstration

71.7 A smoking

lung cancer

o1

-c

ir

c)

8Er

b8_

88,

bronchitis

=o Eo Eb

Eo. c(6 tuberculosis ot the lung

1920

1

940

1950

1960

year

machine

thermometer

First set up the oppqrotus without the cigorette.

Turn on the suction pump for 5 minutes.

1930

rubber tubing

to suction

Look of the temperofure, the colour of the gloss wool ond the colour of the lime woter. Repeot the experiment with the cigorette.

cigarette

lime

glass wool

Other people's smoke Mony non-smokers ore offected by other people smoking. It con irritote their eyes ond give them heodoches ond sore throots, porticulorly if they suffer from osthmo or hoy fever. People who live ond work with smokers con be offected by smoking diseoses including lung concer. People ore becoming increosingly intoleront of possive smoking. Becouse of this smoking is being bonned from more ond more public ploces. In the UK, smoking is now bonned inside ollpublic ploces.

It is olwoys worth giving up if you do smoke. The risk of getting lung concer ond other diseoses folls ofter smokers give up.

t67

Some sports people toke drugs to improve their performonce. They do this becouse: o Medio pressure is put on them to be successful. r They think thot their sporting successes will moke them rich. o They think everyone else is doing it. o They do not think thot they will get cought.

$t

:i

rF# :

a

{.-L

:.l

1

-

Performonce-enhoncing drugs hove been bonned by the

InternotionolOlympic Committee (lOC) to ensure thot competition in sport is foir ond to protect the heolth of sports people.

Types of drug Anqbolic steroids ore substonces similor to the mole

7

\

Ben Johnson won the 100 m title at the 1988 Olympics but was disqualified for taking drugs

sex hormone testosterone.

They work by mimicking the protein-building effects of this hormone. The result is muscle growth, which gives the othlete increosed strength qnd enduronce. There ore o number of hormful side-effects resulting from the excessive use of onobolic steroids. In men, use of these drugs con bring obout increosed oggression, impotence, boldness, kidney ond liver domoge ond even the development of breosts. In women, there is o development of mole feofures, fociol ond body hoir ond irregulor periods.

t

{i

;f

Beto-blockers ore drugs used to treot people with heort problems. When token, they lower the heort rote ond reduce blood pressure. They ore oble to reduce the effects of stress on the body. The IOC hos bonned them in such sports os orchery, shooting, ski-jumping, bobsleigh, biothlon ond modern pentothlon.

t

Canadian snooker player Bill We rbe n i u k took b eta-blockers to steady his aim

such os omphetomines ond cocoine, con give the othlete o lift, keeping them owoke ond competitive. They speed up the reflexes ond reduce the feeling of fotigue.

Stimulonts,

They con be hormful to the body since they increose heort rote ond blood pressure ond reduce the feelings of poin. They con olso be oddictive ond give rise to ponic ottocks ond increosed oggression.

Norcotic onolgesics include methodone, codeine ond heroin. These drugs oct os poin killers thot ore oble to mosk on injury.

The problem is thot if the othlete continues to compete, the injury moy become much worse or even permonent. Some norcotic onolgesics con be highly oddictive.

168 ,:-

Di an e Aloh d ah I s uccessf u I ly proved that she was innocent of drug\aking

Summory o

A drug is

I

total

women

o) Drow o bor chort to show the totol number of deoths for eoch diseose. b) Divide eoch bor into the relevont proportions to show the number of deoths in men ond women. c) Exploin how smoking couses: i) emphysemo iii) lung concer ii) heort diseose iv) bronchitis.

100

680

Number of deaths

6

men

4

-- - - women

0

yeat

o) i) When did men stort smoking ? ii) When did women stort smoking? b) Describe the pottern of cigorette smoking shown by the whole populotion. c) i) Describe the effect of the 19121--18 wor on smoking hobits. ii) Suggest on explonotion for your onswer. iii) Describe the effect of the 1939-45 wor on smoking hobits. iv) Suggest on explonotion for your onswer. d)Whot effect did the RoyolCollege's reports hove on the smoking pottern in: i) men ii) women?

e) Suggest ond exploin reosons for o downword trend in deoths due to lung concer.

Further questions on poge 171

Further queetions on Humons os orgonisms

)

2.

Food ond digestion

1. Neilgoes to o'well mon' clinic for o check up.

The diogrom shows the moin regions of the digestive system in o humon. A

His doctor weighs Neil qnd mecsures his height. He then cqlculqtes Neil's Body Moss Index. He tells Neil he is overweight ond must go on

B

F

o diet. o) Neil weighs 86kg.

His height is 1.68 metres. i) Use the toble to colculote Neil's Body Moss

Index weight in

tll

ks

54 59 64 68 73 77 82 86 91 95

c

100104t09113

137

E

't42 147

152 E 158 o 163 ,= -c

68

o

73

.9)

I

78

D

83

o)Nome the ports lqbelled A, B, C, D, E ond F on the diogrom. t3l b) In which of these structures

188 193 198

i) ore fotty ocids ond glycerol obsorbed [7J ii) is most wqter obsorbed tll iii) does egestion toke ploce ? tll (OCR)

2003

ffi weight

underwelght healthy weight over

ii)

I

obese

Which weight cotegory does Neil belong to? tll iii) Determine how much weight Neil would hove to lose in order to hove o heolthy weight. tll b) Exploin why Neil's doctor colculotes his Body Moss Index, rother thon just weighing Neil, to find out if he is over weight. t2l c) In some oreqs of the world people ore storving. It is importont thot people eot enough protein. The recommended doily ollowonce of protein cqn be determined by using the following formulo. Recommended Doily Allowonce of protein in groms:0.75 X Body Moss in kg i) Colculote how much protein Neil should eot eoch doy. tll ii) Neil hos o teenoge son. Suggest why Neil's son should eot more protein thon Neil. t1l (OCR)

3.

The toble below gives some informotion obout the nuhitionol content of o hoditionql beefburger qnd of o similor non-meot vegetoble burger. Vegetoble burgers ore mode from o mycoprotein, coloured qnd flovoured to toste like beef. Contents per 1009

Beefburger

Vegetable burger

energy

1192kJ

970 kJ

protein

15.0 g 3.7 g 23.8 g 0.5 g

18.59

o.4g

4.59

carbohydrate fat sodium**

fibre

11.7 g 12.7 g 1.3 g

**mostly os sodium chloride

o) i) Which 'burger' hos the higher protein ii) iii)

Note: although a question may be marked (AQA) etc,

1009? beefburger?

content per t1l How much protein is present in 120g of t1l In which orgon of the body ore corbohydrotes stored

?

it will often be relevant to other examinations as

tll

well. 177

Further questions on Humons os orgonisms

iv)

Nome the corbohydrqte which is stored in this orgqn. ttl b)Stqte two reosons why o person who is qnxious to eot o heolthy diet might choose the vegetoble burger rother thon the beefburger. Give on explonotion for the choice in eoch cose. t4l (OCR)

4.

Food substonces need to be digested before they con poss into the blood. Mony foods contoin fot. o) Whot ore the products of fot digestion? [1] b) The liver produces o chemicol substonce colled bile which is odded to food during digestion. Exploin how bile helps in the digestion of fqt. tsl c) Describe one effect of eoting too much food rich in onimql (soturoted) fot qnd exploin the problems this moy evenfuolly produce in the body. t2l (EDEX)

)

Breothing ond respirotion

5.

o) Exploin, os fully os you con, why respirotion hos to toke ploce more ropidly

(cm3 per kg per min)

A

78.6

48.9

B

67.5

55.1

c

63.0 57.4

58.7 64.6

i) ii)

lung

lung

diaphragm

X.

o)Nome the tube t1l b) Exploin how tube X is kept t1l c) Why is it necessory to keep tube X open? [1] d) Exploin whotwould hoppen lotheoolume ond pressure of oir inside the lungs when the chest wqll ond diophrogm ore moved in the

t3l

open.

direction shown by the t2l e) Whot mokes the diophrogm move in the direction shown [t]

f)

?

The volume of oir breothed during three different octivities is shown on the groph.

A

BC

F

.=! tEg 2 O:o oQ I =6 6E >o

0

0 5 10 150 5 10 15 0

5 1015

time in seconds

i) ii) iii)

Whot wos the number of breoths per minute during the octivity between C ond D Whot wos the volume of oir exchonged per breoth during the octivity between E ond Copy ond complete the toble by selecting from the list below the most oppropriote octivity.

?

tll

F?

tll

hord, resting,

Activity between

(AOA)

DE

E

running

Whqt is the relotionship between moximum rqte of oxygen consumption ond time for o 10 mile roce ? [1] Suggest on explonotion for this

relotionship.

chest wall

Best time in 10 mile race (minutes)

D

772

Maximum rate of oxygen consumption

The diogrom shows the breothing system of humon.

qrrows.

during exercise. t2l b) During exercise the process of respirotion produces excess heot. Exploin how the body prevents this heot from cousing o rise in the core (deep) body temperolure. [4] c) In on investigotion four groups of othletes were studied. The moximum rote of oxygen consumption for eqch othlete wos meosured ond the meon for eoch group wos cqlculoted. The othletes then rqn 10 mile roces ond the meon of the best times wos colculoted for eoch group. The results ore shown in the toble below. Group of athletes

6.

iogging

Activity

AandB CandD EandF

t3l

(ocR)

Further questions on Humons os orgonisms

7. The informotion

below wos found on o

ii)

cigorette pocket.

How mqny white blood cells cqn be seen on the slide

?

[2]

Warning: SIVIOKING CAN CAUSE FATAL DISEASES

two respirotory diseoses which could be coused by cigorette smoking. t2l b)The diogrom below shows on olveolus o) Nome

(oir-soc). wall of alveolus B

SG

capillary wall

A

b) i) Whot is the function

ii)

direction of blood flow red blood cells

i)

Through how mony cellloyers must oxygen poss to leove the oir in the olveolus ond reoch o red blood cell? fil The toble below shows the relotive concentrqtions of goses dissolved in the blood qt the ends of the copillory shown in the diogrom. Gas

End A

End B

Carbon dioxide Oxygen

low

ii) Copy ond complete the toble using the words high ond low. t2l c) i) Nome o type of blood cell not shown in the diogrom. tll ii) Exploin how the cell nomed in c) i) is involved in the body's defence ogoinst diseose. t1l (OCR)

) 8.

Blood ond circulotion The diogrom below represents o smeor of blood on o microscope slide. o) i) How mony red blood cells con be seen on the slide ?

cells

?

of the red blood

fl

Give two woys in which red blood cells ore odopted to corry out this function. [2J c) Exploin how corbon monoxide offects the woy in which red blood cells function. t1l d)Red blood cells survive on overoge obout 100 doys. New cells hove to be produced in the bone morrow. i) Whv ore red blood cells not oble to reproduce t1l ii) 1mm3 of blood contoins 5 million red

?

blood cells. How mony red blood cells does 1cm3 (1000mm3) contoin? tll iii) An qdult hos 5000 cm3 of blood. How mony red blood cells hove to be mqde on overoge eoch doy in the bone morrow? Show your working [2] e) In some people the bone morrow is diseosed ond unoble to produce enough red blood cells. These people moy need o bonsplont of bone morrow from onother person. Exploin how eqch of the following moy help to prevent the rejection of the tronsplonted bone morrow. i) Use bone morrow from o brother or sister of the potient. t2l ii) Giving the potient drugs which stop the octivity of the white blood cells. t2l f) After the honsplont operotion the potient hos to be isolqted from other people for some time. Exploin why. t2l (AOA) 773

Further questions on Humons as orgonisms

9. Doctors think thot there

is q link between

heort diseose ond the level of cholesterol in the blood. Heolthy levels of cholesterol ore below 5 units. The toble below shows the percentoge of odults whose cholesterol level is qbove 5. Age

Percentage of men

Percentage of women

15-24

22

26

2fr4

48

42

3544

66

56

45-54

74

68

55-64

78

86

65-74

74

88

75 and over

68

86

chonges with oge. t2l c) Describe how the level of cholesterol in womon, chonges ond compores with men over 50 yeors of oge. Suggest o reoson for your onswer. tsl d)High levels of cholesterol con block coronory orteries. i) Exploin whot this will do to the flow of blood through these orteries. tll ii) Suggest why this cqn be hormful to the (ocR)

10. Domoged heorts con be reploced.

Some potienh hove on qrtificiol heort. Others hove o reol heort. o) Use the following words to describe the

odvontoges ond disodvontoges of using on ortificiol heort. drugs power supply rejection size [4] b)When q donor heort becomes ovoiloble, most of the heort potients who need it connot hqve it tronsported. Exploin why. tsl c) There is o shortoge of reql heorts from donors. Some people olwoys com/ o donor cord. 174

t2l Some doctors think thot they should be oble to use orgons from deod bodies without permission unless the person corried o cqrd soying they did not wish to donote orgqns. Exploin with reosons whether you think this point of view should be

low.

t2l

(OCR)

11. Three pupils were osked to find out who wos

doto.

t2l

ii)

mode into

q) Use the informotion in the toble to conshuct q bor chqrt to disploy the t2l b) Describe how the pottern for the percentoge of men with high cholesterol

heort.

Some people think thot everyone should be mode to corry o donor cord by low. Other people do not ogree with them. i) Exploin with reqsons, the orguments for ond ogoinst corrying donor cords.

the fittest. They decided to do this by meosuring their pulse rotes. This is whot they did. 1. They counted their pulse rotes when sitting down. 2.They then exercised for three minutes in different woys: Peter ron up ond down the stoirs; Morgoret did step-ups; John ron on the spot. 3. They counted their pulse rotes os soon os the exercise stopped. .They counted their pulse rotes three minutes ofter the exercise stopped ond ogoin six minutes ofter the exercise stopped. Their results qre shown on the groph below.

^1 o fl

10

c 'Et 00 o o 90 o (6

o

.o

o

If o

80 70

60 50

012345678910 time (minutes)

o) Whot wos Morgoret's pulse rote three

minutes qfter exercise

?

t1l

Further quections on Humons os orgonisme b)They concluded thot Peter wos the fittest

13. The diogrom shows the meon doily input ond

person. Give one reoson why they reqched this

conclusion.

ttl

c) Suggest two woys they could hove

improved their investigotion.

)

output of woter for on odult.

t2l

(AOA)

water gain

water loaa

food 1000cm3 atr

drink 1200cmo

350cmg

Homeostosis

skin 500 cmg

12. The regulotion of body temperoture

is

ochieved by boloncing energy releose ogoinst energg loss. Energy releose is greoter

during exercise. o) The rqte of metobolism chonges during exercise. Describe how this influences energy releose. t2l b)Exploin why, during exercise, the body ottempts to lose more energy. t2l c) Whqt role does negotive feedbock ploy in reguloting body temperoture ? tll d) During rest, excess sugor is stored. How is this ochieved? t2l e) The grophs below show how the blood glucose ond the concenhotion of hormone involved in glucose storoge vory over q 12 hour time period. i) Using these grophs exploin why o single doily dose of hormone would not odequotely conhol blood glucose concenhotion in diobetics. tzl

respiration in all cells

150cmg

o) Respirotion is o source of woter. Copy ond complete the equotion for respirotion sugor * .... --* woter + .... + energg t2l b) The kidneys keep the woter content of the body constont by conbolling the volume of woter possed out in the urine. Use doto from the diogrom to colculote the meqn doily output of woter in the urine. Show your

i)

ii) I t

I

E c 6 f

o

unne

300 cmo

working.

t2l

Describe how the omount of woter in the body is contuolled by the kidneys.

t3l c) Sometimes kidneys foil. Two wogn of tuieoting

\z

kidney fqilure ore the use of o kidney diolysis mochine ond kidney tonsplonb. Describe whot hoppens to the composition of o potient's blood os it posses through o

8am 10am noon 2pm 4pm 6pm

8pm

time of day

key:

ii)

concentration of hormone

Exploin how physicol exercise would influence the production of the hormone involved in glucose

storoge.

t2l

mochine.

t3l

d) In the heqtment of kidney foilure: Give two possible odvontoges of using o kidney tronsplont rqther thon o diolysis t2l Give two possible disodvontoges of using o kidney mochine rqther thon o (AOA) diolysis

i)

blood glucose

-----

diolysis

(OCR)

ii)

mochine.

mochine.

t2l

175

Further questions on Humons os orgonisms 14. The kidneys remove wqste moteriols from Pituitary gland

the liquid port of the blood. The toble below shows the concentrotion of certoin substonces:

o o o

in the liquid port of the blood in the liquid thot hos just been filtered from the blood in the kidneys in the solution in the blodder.

o)

i)

Pituitary gland produces ADH Pituitary gland produces ADH

Person exercises

Which one of these substqnces does not poss into the liquid thot is filtered in the kidneys ? tll

ADH transported to kidney

Concentrataon (%)

Substance

in liquid part of blood

in liquid that has been

filtered in

lncreased reabsorption of water by kidney

in liquid in the bladder

the kidneys

b) i)

protein

7.0

0

0

salt

0.35

0.35

0.5

glucose

0.1

0.1

0

urea

0.03

0.03

2.0

ii)

ii) Suggest on€ reoson why this substonce does not poss out of the blood. tll b) Exploin why the concentrotion of ureo in the liquid in the blodder is much greoter thon the concentrqtion of ureo in the liquid thot is filtered in the kidneys.

tll

c)

i) mqchine works. t3l ii) Use the doto in the tqble to suggest Describe how q kidney diolysis

Using informotion from the diogrom describe ond exploin the sequence of events when the person stops exercising ond drinks o pint of wqter.

t5l Exploin why the response to this chonge would take20 minutes.

t1l

)

Control ond coordinotion

16. The diogrom shows o finger touching o hot object.

It olso shows neurones A, B ond C, which poss electricol impulses from touch receptors to muscle effectors. Neurones D qnd E poss impulses to qnd from the brqin.

onswer. [2]

from touch receptors

shows the effect of o chonge in the woter

content of the blood. o) i) Whot type of substonce is ADH? t1l ii) Whot is the stimulus which cquses the pituitory glond to produce ADH? t1l iii) Precisely how is the ADH tronsported to the

kidney?

776

t

(AOA)

15. The diogrom ot the top of the next column

tll

trom brain

to brain

the concentrqtion thot the solt in the diolysis fluid should be.

Exploin your

(AoA)

to muscle effectors

t

heat

Further questions on Humons os orgonisms

iii)

o) Nome the pothwoy of electricolimpulses

C.

I) Stote which of the hormones is responsible for ovulotion. t1l II) Use the informotion in your groph ond the toble to help you exploin your onswer to port I) obove. t2l b) Stote two medicol uses of sex hormones in humons. t2l (WJEC)

tll tll

olong neurones A, B ond b) Whot is the response of the muscle

effectors?

c) Neurones D ond E ore not involved in the response of the muscle effectors. Whot is the odvqntqge of d) If one of the neurones A, B, C, D or E is cut, it moy offect the obility to respond if you touch o hot object, or the obility to know thqt you hove touched it. Copy ond complete the toble by putting the correct letter in eoch box.

this?

tll

)

Diseose

18. o) The diogrom shows o bocteriol cell

wall

lnformation about neurone

Letter of neurone

lf this neurone is cut, you can remove your finger from a hot object, but you will not know that you have touched it.

membrane

lf this neurone is cut, you cannot remove your finger from a hot object even though you know you have touched it.

lf this neurone is cut, you cannot remove your finger from a hot object, and you will not know that you have touched it.

A bocteriol cell is smoller thon o humon cell. Give two other woys in which the bocteriol cell is different from q cell in the

(3)

(EDEX)

17 . The toble shows the levels of the sex

hormones oestrogen ond progesterone in the blood streom of o womon during one complete menstruol cycle. Level

oestrogen

0

50 54 66 52 50

7 14 21

28

q) i) ii)

body.

t2l

t2l

of hormone in blood stream (arbitrary units)

Day

humon

b) Describe ond exploin two noturol defences which help to prevent bqcterio entering ond horming the humon body.

c) The toble shows chonges in resistqnce to the ontibiotic penicillin in one species of bocterium between 1991 ond 1996. Years

progesterone 46 40 58

112

Percentage of cases where bacteria were resistant to penicillin

1

991-92

7

1

993-94

14

1

995-96

22

46

A doctor wos osked to heot o potient who hod o sore throot. i) How does penicillin help to treot

Plot the dqto for the hormones oeshogen ond progesterone os line grophs on one grid ond join the

plots.

How mony units of oeshogen ore in the blood sheom on doy 18 ?

t3l t1l

ii)

infection?

Use the doto in the tqble to suggest why the doctor should not prescribe

penicillin.

t2l

tll

(AOA)

L77

Further questions on Humons os orgonisms 19. o) Stote which pothogen couses eoch of the following diseoses. Choose from the following list.

bocterio fungus protozoo

_o FC ;o

5R

virus

so

.e8 co

i) influenzo ii) cholero iii) dysentery

'fr9

iv)

EE EO

o-6

20

Eo-

othlete's foot

10

:p 1C

b)The humqn body hos vorious woys of defending itself ogoinst pothogens. Look ot the diogrom of the body ond exploin how eoch lqbelled port helps to (OCR) protect us from diseose. t4l

mucus membranes in nose and trachea

ff[[

o

.tT;,l,

instructions instructions

c) Kidney tronsplonts were introduced in the twentieth century os one woy of heoting potients with kidney fqilure. i) Give one other woy of treoting kidney

ii)

blood

foilure.

t1l

The potient's body moy reject o tronsplonted kidney unless doctors toke precoutions. Some of these precoutions ore listed below. A donor kidney is speciolly chosen. o The recipient's bone morrow is heoted with rodiotion. o The recipient is heqted with drugs. o The recipient is kept in sterile conditions. Exploin how eqch of these precoutions moy help the potient to survive.

.

hydrochloric acid in stomach

t4l

20. In the eighteenth century surgeons did not weor speciol clothing or wosh their honds before operotions. Mony of their potients died from infections. o) Suggest why potients often died from infections ofter t1l b)ln the nineteenth century Joseph Lister told surgeons to use sproys of corbolic ocid in operoting theotres ond to wosh their honds. The groph ot the top of the next column shows the effect thot using Lister's instructions hod on the number of potients who died from infections ofter

(AoA)

21. o) The conversion of proteins to omino ocids con be represented os shown below. protein

operotions.

surgery. Describe how Lister's instructions offected

the number of potients dying from infections ofter

surgery.

778

t2l

",ino""id"&iWq i)

ii)

Whot nome is given to the breoking down of proteins into omino ocids in the body t1l Stote one use of qmino qcids in the

?

body.

ttl

b)Antibodies ore proteins produced in the blood by the immune system when the body is infected.

Further queetions on Humons os orgonisms

i) ii)

Which port of the immune system produces qntibodies ? tll The effectiveness of o person's immune system con be reduced by the use of drugs. Stote one other woy this con hoppen. tll iii) If o person hos q kidney or other orgon tronsplont, drugs ore given to reduce the effectiveness of the immune system. Exploin the reoson for this. t2l c) Active immunity is o permonent type of immunity goined os o result of the body reocting to on infection. Possive immunity is o temporory type of immunity where ontibodies ore given to the body, often by injection. A boby moy ocquire possive immunity other thon by meons of on injection. Stote one woy. tll d)A groph of o person's immunity is shown below.

loborotory ond tried out on heolthy humon volunteers before use with potients. Tholidomide wqs developed os o sleeping pill. Unfortunotely, mqny bobies were born with limb obnormolities to mothers who took Tholidomide to relieve morning sickness during pregnoncy. i) Exploin why o new drug is given to heolthy humon volunteers in o drugs

ii)

triol. its side

gives informotion obout the qmounts of olcohol consumed ond the number of deoths from liver diseqse in some counhies. Mean amount of alcoholconsumed per person per year

level

(litres)

1234567891011121314 time in weeks

immunity ? Exploin the reoson for your onswer.

t2l

22.

(AoA)

Drugs o) Scientists qre constontly developing new drugs. All drugs need to be tested in the

per 100000 people per year

8

4

France

17

34

Germany

13

27

4

1

15

22

6

12

Spain

refers hove octive or possive

Number of deaths

from liver diseased

England

lceland

i) For how long wos the person immune ? tll ii) Does the person to whom the groph

t2l

23. The toble

antibody

)

effects.

b)Some people think thot smoking connobis con relieve the symptoms of the diseqse multiple sclerosis. Exploin, using scientific ond ethicolreoson, why most doctors would not qdvise their potients to smoke (AOA) connobis for this purpose. tsl

County

antibodies given

t1l

Exploin why the results of the Tholidomide drug triqldid not identify

Sweden

o) Drow q bor chort to show this

informqtion b)Alcohol couses horm to the liver. Exploin how the informotion provides evidence of

this.

tll

c) The meon olcohol consumption is lower in Germony thon in Spoin. However, the deqth rqte from liver diseose is higher in Germony thon in Spoin. Suggest one (AOA) reoson for

this.

t1l

t79

Further questions on Humons os orgonisms

diseoses. The bor chorts on the next poge show the link between cigorette smoking ond

these diseqses. Look qt the chorts.

o) How does cigorette smoking offect eoch of these two lung diseoses ? Emphysema

Blood alcohol level in mg per 100 cm3

Alcohol

24. Emphysemo qnd tuberculosis ore lung

consumed per hour

37

45

19

22

6 units

75

90

37

45

12 units

150

180

70

90

24 units

300

360

150

180

ii) With people who consume the some

25 20

iii)

'15 '10

5 0 5

'10

15

20

mole on the grid provided. On the some groph, plot the doto for 90 kg mole. Join the points with shoight

40 35 30

ii)

25 20 15 10

5 0

omount of olcohol, whot is the relotionship between their blood qlcohol level ond body moss? t1l With people of the some body moss who consume the some omount of olcohol, whqt is the relotionship between their blood olcohollevel ond

their sex? tll b) i) Plot o groph of the doto for the 45 kg

25

cigarsttes smoked per day

cases per 100000 p6ople

lines.

tsl

In certoin countries, the legol limit for driving is 80 mg of olcohol per 100 cm3 of blood. From your groph, how mony units of olcoholper hour would o 45 kg mole drink to reoch the

legollimit?

t

in the blood olcohol level of the 45 kg mole ond the 90 kg mole ofter drinking 20 units

per day

of olcoholper

b)Smoking con couse other diseoses. Look qt the list of diseoses:

othlete's foot c(mcer diobetes heort diseqse influenzo (flu) sickle cell qnqemio Write down two diseoses which con be coused by smoking. Choose your qnswers from the list.

t2l

tll

iii) Whot is the difference

25

:t *"-"':",*":

(ocR)

shows the relotionship between olcohol consumed qnd blood olcohol levelfor moles ond femoles of different body moss.

o) i) Whot is the relotionship between the qmount of olcohol consumed ond the blood qlcohollevel? t1l

hour?

tll

c) The toble below shows how increosing levels of blood qlcohol con result in chonges in behoviour. Copy ond complete the toble by noming the port of the brqin thot would be offected. One box hqs been completed for you. Blood alcoho! level in mg per 100cm3

Behaviour change

Part of brain

affected Cerebral hemispheres

50

Less able to make decisions

100

Loss of balance

200

Double vision

400

Respiratory failure

25. The toble ot the top ofd the next column

180

Female 90 kg

Male 90 kg

3 units

30

Tub6rculosis

Female 45 kg

40 35

cases per 100000 people

Male 45 kg

(3)

(EDEX)

il

chapter 72

fsuillnU

I

I Plnltts

Whot's the most common colour in noture ? Most of the green we see comes from leoves. Why ore they this colour ? If you look ot some leof cells under the microscope whot do you see ? Lots of round, green structures colled

chloroplosts. Whot do you think they ore used for

?

We collgreen plonts the producers.

Why do you think this

is ?

Green plonts ore oble to mqke their own food from simple row moteriqls oround them. This process is colled photosynthesis. Energy is needed for photosynthesis. This energy comes from sunlight.

Chlorophyll

Chloroplasts in moss cells

is o substonce thot obsorbs sunlight.

Chloroplosts contoin lots of chlorophyll. The light energy is used to convert corbon dioxide ond woter into sugor (glucose). The sugor is the plont's food. Oxygen is mode os o by-product.

light energy

During photosynthesis the energy from sunlight becomes converted into the chemicolbond energy in the glucose.

Photosynthesis is not o simple reoction. It tokes ploce in o number of smoll stoges. This is the equotion for the whole process

corbon dioxide 6

CO2

+

water light ond chlorophyll 6 HzO

glucose + oxygen c6H12o5, 60,z

181

Green plonts moke food from simple substonces. We con see from the equotion on the previous poge thot glucose is mode. Experiment 72.1. Tbsting a plant for glucose A Put o piece of rqw onion in o pestle ond mortor. eye protection Grind it up with o little sond ond 10 cm3 of woter. Filter the liquid into o test-tube. Heot the liquid with on o woter both.

1.0

drops of Benedict's solution

Did the liquid turn oronge

?

If too much glucose is dissolved in the cell sop it would moke o strong solution. This would drow woter in from other cells by osmosis. Storch is insoluble ond does not couse this problem. This is why insoluble substonces like storch ore used for storoge in plonts.

Experiment 72.2 Testing a leaf for starch Dip o leof into boiling woter for obout o minute to soften it. Turn off the Bunsen burner. Put the leof into o test-tube of ethonol. Stond the test-tube in o beoker of hot wqter

for obout 10 minutes.

A A

Starch grains provide an insoluble store of food

eye protection boiling water

ethanol

ethanol is flammable

Wosh the leof in cold woter.

Spreod the leof out flot on q Pehi dish ond cover it with iodine solution. If the leof goes blue-block, storch is present

iodine

o

Why is it importont to turn off the Bunsen burner when you were heoting the ethonol?

o

Why wos it necessory to extrqct the chlorophyll before you tested for storch ?

182

turn Bunsen off

)

Row moteriols for photosynthesis

Whot do plonts need for photosynthesis

?

We hove olreody soid thot light energy is needed to power the process.

If you look bock ot the equotion on poge L81 you will see whot else is needed.

o Chlorophyll

obsorbs the light energy. Chlorophyll is in the chloroplosts of the leqf

o Corbon dioxide diffuses o Woter

into the leqves from the oir

is obsorbed by the roots from the soil.

We con corry out experiments to show thot these

;oe

row moteriols ore needed for photosynthesis. ollthe things thqt it needs except for the one foctor thot we ore investigoting.

We simply give the plont

9",

If the plont is unoble to corry out photosynthesis it will not moke storch. But we must moke sure thot the plont hos no storch to begin with. We con de-storch os plont by leoving it in the dork for 24 hours.

a ,

'' 'q-'

.

t*

Help, l'm being de-starched!

Experiment 72.3 ls chlorophyll needed for photosynthesis Toke o de-storched, voriegoted geronium plont. (Voriegoted meqns some ports of the leoves ore white becouse there is no chlorophyllthere.)

?

Plqce the plont in sunlight for q few hours.

Drqw one leqf to show the white ond green ports

A

Now test this voriegoted leqf for stqrch.

eye protection

o

Did only the green ports of the leof go blue-block ? Why did this hoppen ?

o Why didn'tyou exhoct chlorophyllfrom the leof ond then see if it could corry out photosynthesis

?

Variegated geranium leaves

183

From oir ond woter

sugar made in

How could you prove thot o plont needs corbon dioxide to moke its own food ?

carried to all parts of the

the leaves is

Provide it with everything it needs for photosynth esis except corbon dioxide. Then test to see if it hos mode storch.

orygen

ffi

passes out

carbon dioxide

water and

is taken in

minerals are taken from the soil by the roots

Experiment 12.4 Is carbon dioxide needed for photosynthesis? Toke o de-storched geronium plont. Enclose it in o plostic bog with q chemicol thot obsorbs corbon dioxide. (Sodo lime obsorbs corbon dioxide.) Leove the plont in sunlight for o few hours. eye Test o leqf for storch. protection

A

o Does the leof contoin stqrch ? Why not ? o Hqs the plont cqrried out photosynthesis ? o Whot would be your control plont?

plastic bag

soda lime

elastic band

A controlplont should hove everything it needs for photosynthesis including cqrbon dioxide.

Experiment 72.5 Is sunlight needed for photosynthesis? Toke o de-storched geronium plont. Cover port of the leof with some tin foil (this prevents light getting through). Leove the plont in sunlight for q few hours. A lA Test the leof for storch.

o Which ports of the test leof go blue-block?

o

or*"Jfton

Why do the ports thot were covered not contqin storch ?

Plonts olso need woter for photosynthesis. Con you think up o simple experiment to prove this ? It's not eosy is it ? If you remove ollthe woter the plont willshrivel up. Scientists con give plonts o speciol form of woter

colled 'heovy woter'. They con troce this woter ond see where it goes. They con show thot it is token up ond used in photosynthesis. 184

aluminium

starch present no starch

r

)

Products of photosynthesis

Let's remind ourselves of the photosynthesis equotion

corbon dioxide

*

woter

jglffgfchlorophyll

glucose

"

+

:

oxygen

So how ore the products of the reoction useful? Most photosynthesis tokes ploce in the leoves. So most of the food is mode there. But oll ports of the plont need food. Dissolved food is corried qround the plont in its

tronsport system. Whot hoppens to it then ?

o

Some of the glucose is used in respirotion to give the plont energy.

o

Some of the glucose is chonged to storch ond stored in the roots for future use.

o

Some of the glucose is used to moke cellulose. This is needed for plont cellwolls.

Photosynthesis makes food

Glucose con olso be converted to other substonces:

o

o

Plonts get nitrogen by obsorbing nitrotes from the soil. Glucose ond nitrogen con form omino ocids. Proteins ore built up from omino ocids. Plonts need proteins for growth ond cell repoir.

Cellulose strands in a plant cell wall

Fqts ond oils ore used for storoge in seeds.

Oxygen is olso o product of photosynthesis. This reploces the oxygen thot is used up in respirotion. Experiment 72.6 Oxygen produced in photosynthesis Set up the opporotus to collect bubbles of gos given off by the pondweed. gas collecting Dissolve o little sodium hydrogencorbonote in the woter. Ploce the opporotus in the light. Test the gos for oxygen with o glowing splint. sunlight o Wh9 wos hydrogencqrbonqte sdded to the woter? \ o Whg is it importont to leove o gop between the beoker qnd the funnel ? plasticine Wqter rich in corbon dioxide circulotes to the pondweed suppoft ond increoses the rote of photosynthesis. o Why is it essentiqlthot o woter plont like Conodion pondweed is used in this experiment ? (Htn:t: Thlnk,about how the gos is collected.) o Why is tte,ggs collected unlikely to be pure oxygen ?

Canadian pondweed

185

)

Why is photosynthesis importont

=tk

?

: +-*.

Think obout the food you've eoten in the lost24 hours. How much of it come from plonts ?

t

i

eq', f

How qbout rice, pototoes, corn flqkes ond peonuts for o stort ? And whqt obout the steok or the beefburger Where did they come from ? From onimols thot hove eoten plonts.

I

q*,# ?

Then there ore things like cooking oil ond low-fot morgorine. They ore mode from ports of plonts. Without plonts we would soon get pretty hungry

I

lnuestigation 1.2.7 Food plants Look qt some food plonts like the ones shown here rhubarb

Try to soy whot parts of plonts they ore. For instonce, celery is o leof stqlk.

garlic corn-on-the-cob

Drow some ports of the plonts thot we eqt. Write o note to soy whot eoch port does in o living plont. Corry out some food tests on different plont ports. Tiy testing corrot, onion, pototo ond different seeds Test for sugor, storch, protein ond fot. (See Experiments 4.L, 4.2, 4.3, 4.4, poges 43-5)

o Medicines

tomato

hove been extrocted from hundreds of

species of flowering plonts. Tropicol roinforests ore the moin source of these plonts.

o Hqbitots

ore provided by plonts.

The roinforests moke up only 6% of the Eorth's lond surfoce. But they support more thon holf the world's species of onimols ond plonts.

o Atmospheric

goses ore kept stoble by photosynthesis Without green plonts, corbon dioxide in the oir would increose ond oxygen would decreose.

These ore powerfulreosons why the destruction of

tropicol roinforests should be stopped.

o

Plonts olso provide us with building moteriols like wood. Fuels like oil, cool ond peot hove come from fossilplonts

186

A

eye protection

okra lettuce

Food parts from plants

)

Rote of photosynthesis

Rote olwoys involves time. The rote of photosynthesis could be meosured by how much glucose is mqde in o given time. So why ore people interested in this ? Well, the foster photosynthesis tokes ploce, the more

food is mode ond the bigger the plont will grow Scientists try to increose the rote of photosynthesis to increose the yield of o crop. Whot sort of things would offect the rote of photosynthesis ? Sugor cone is o crop thot grows well in the tropics. Does the climote offect the rote of photosynthesis ?

Cutting sugar cane light is

a

Light

so

Photosynthesis increoses when light gets brighterbut only up to o point. When o certoin light intensity is reoched the rote of photosynthesis stoys constont. It con't go ony fqster even if the light intensity continues to rise.

o o o

something else is limiting the rate

t I

c

Experiment 72.8 Photosynthesis ond light intensity You con use this opporofus to meqsure the effects of light intensity on the rqte of photosynthesis: Cut o piece of Cqnodion pondweed qbout 5 cm in length You con weigh down the other end with o poper clip. Count the number of bubbles releosed with the lomp ot different distqnces owoy from the plont.

o

limiting the

=oo 0)

(!

light intensity

Canadian pondweed

stream of bubbles

Did the number of bubbles increose when the lomp wos neqrer to the plont? Why do you think this wqs ?

metre rule

Mony plonts spreod their leoves to cotch os much light os os they con. But light thot is too strong con domoge the chloroplosts. Some woodlond plonts prefer dim light. We collthem shode

plonts.

They ore oble to moke use of the limited omount of light thot penetrotes the tree conopy ond reoches the woodlond floor. Bluebells

187

)

Limiting foctors

Things like light intensity con offect the rote of photosynthesis-we coll them limiting foctors. It doesn't motter if the plont hos lots of corbon dioxide ond woter ond o nice worm temperoture. If light is in short supply, then light will limif the rote of photosynthesis. Let's soy light intensity is limiting photosynthesis. The only woy to increose the rote is to incresse the limiting foctor-in this cose, light intensity. Other limiting foctors ore corbon dioxide ond temperoture But only one foctor con limit the rote of ony one time. It depends on which one is in the shortest supply.

Temperoture

G/asshouses can control limiting factors

c 9o

An increose in temperoture usuolly increoses the rote of photosynthesis. Most chemicol reoctions increose with temperoture But ot obout 40 "C the rote slows. At temperotures obove this, the rote drops quickly. This is becouse the enzymes in photosynthesis ore being destroyed. Inuestigation

72.9

a

o

s

u

Plan an inuestigation into the effect of temperature on the rate of photosgnthesis (Hint: You could hy the opporotus in Experiment 12.8 using different woter boths.) Remember thot other foctors like light intensity ond corbon dioxide concentrotion must be kept constont. Check your plon with your teocher before you stort.

Why do you think thot crops like gropes ond melons grow better in o glosshouse ? The worm conditions inside the glosshouse increose their rote of photosynthesis. In this woy we con grow plonts thot would not normolly grow in the UK. Different types of plonts hove different temperotures ot which they grow best. Eoch hos on optimum temperoture for growth

188

Corbon dioxide The more corbon dioxide you give plonts, the more photosynthesis they corry out. It is not possible to do this with crops outdoors. The oir usuolly contoins qbout 0.04"/" corbon dioxide

Why do you think thot cqrbon dioxide is often odded to glosshouse crops ?

Look of the picture of lettuces grown in o glosshouse: Those in A ore growing in oir which hqs more corbon dioxide thon those in B. Which would sell for the best price Why ore these lettuces bigger ?

?

Inuestigation 12.70 What is,the efiect of carbon dioxide on the rate of photosynihrxis ? How could you chonge Experiment 72.8to find out the effects of Ccifbon dioxide ? These fqctors con limit the rqte of (Hint: Adding sodium hydrogencqrbonote to woter photosynthesis: increoses the concentrotion of corbon dioxide.) o light intensity Remember, other foctors like light intensity ond o temperoture temperoture must stoy constont. :''. corbon dioxide concentrotion

r

Check your plon

*ith your teocher

These qre colled

before you stort.

So if we provide more corbon dioxide, photosynthesis will be oble to work qt o foster rote. There is not very much corbon dioxide in the otmosphere,only obout 0.04 %. Look ot the groph: Whot is the limiting the rote of photosynthesis ot point X? Whqt is the limiting the rote of photosynthesis ot point Y? Whot hoppens to the rote of photosynthesis if the

limiting fqctors

o.4%

,9

o

co2

to E

o o o

too o (6

v

0.o4%

coz

corbon dioxide concentrotion is increosed from 0.04"/"to 0.4%? Once ogoin, this meons more food con be mode.

light intensity

189

)

Leoves

Whot words would you use to describe o leof Flot? Thin? Green?

?

The leof is where photosynthesis tokes ploce. It is very well odopted for this job. Leoves hove:

o a large surface area-to obsorb light roys o a thin shape-so goses con diffuse in ond out eosily o green chlorophyll - to obsorb light

o

ueins-to support the leof surfoce ond to corry substonces to ond from ollthe cells in the leof.

Experiment 12.17 Looking at leaues Look closely ot eoch surfoce of o leof with o lens

o Is the upper surfqce glossy ? Why is this ? o Which surfoce is the dorker green ? Does most light get to this surfoce

?

On the inside To find out how o leof works we need to look ot o thin slice under the microscope

chloroplasts.Light goes straight through

cuticle : waterproof layer that also cuts down the water lost by

palisade layer : the

evaporation

spongy layer : more rounded cells with lots ol air spaces between them. Gas exchange

palisade cell contains lots of chloroplasts. Most photosynthesis occurs here

i

'

occurs here

lower epidermis : no thick cuticle. Has lots of tiny holes called stomata (singular stoma) 1. These allow gases to diffuse in and out

Experiment 12.12 Looking at a leaf section Put o slide of q section of o leqf on the microscope Look for these structures under low power. Now look ot eoch type of tissue under high power.

190

upper epidermis : single layer of cells with no

vein : contains tubes called xylem that bring water and salts to the leaf and tubes called phloem that take dissolved food away

)

Stomoto

Stomoto ore smoll holes on the underside of the leof thot let goses diffuse in ond out. (The singulor of stomoto is stomo.)

o Corbon dioxide diffuses in for photosynthesis o Oxygen mode in photosynthesis diffuses out. o Woter vopour diffuses out. Experiment

12.13

palisade cells

Where are the stomata?

Try dropping o leof into o beoker of boiling woter From which surfqce do bubbles oppeor? Whot is the oir coming out of ?

Why ore most stomoto on the underside of the leof Whot might block them on the upper surfoce ? Would more woter be lost by evoporotion if they were on the upper surfoce focing the sun or on the shoded lower surfoce ?

a a

spongy cells ? lower epidermis

gua

Carbon dioxide diffuses into the leaf for photosynthesis

Opening ond closing Stomoto con be opened ond closed by guord cells

guard cells pore

Stomoto usuolly open during the doy. Woter posses into the guord cells by osmosis. This mokes them bend so the stomo opens. Corbon dioxide diffuses into the leof for photosynthesis chloroplast

The stomoto close of night. Woter posses out of the guord cells by osmosis. They stroighten up so the stomo closes.

stoma pore open

The stomoto qlso close in hot dry weother. Why do you think this is ? Would the plont stoy upright if it lost o lot of woter?

Experiment 12.14 Looking at stomata Point o smollsquore (1cm x 1cm) on the underside of o leof with nqil vornish. The noil vornish mokes on imprint of the leof surfoce. Woit for the vornish to dry completely then peel it off. Put it on o slide with q drop of woter ond cover-slip. Observe ond drow two or three stomoto of high power under the microscope. Repeot for the upper surfoce of the leof.

191

)

Gos exchonge

Photosynthesis carbon dioxide + water

Allliving things, including plonts, corry out respirotion. Whot gos do they need for this ? Whot gos do they get rid of ? For respirotion plonts need

ResDiration

'

glucose + oxygen

+

glucose + oxygen

+

carbon dioxide + water

bright dayl carbon dioxide taken in for photosynthesis

to:

o toke in oxygen, and o give out corbon dioxide.

D

D

carbon dioxide given out by respiration

oxygen taken in for respiration

Respirotion tokes ploce all the time Con you think of when corbon dioxide ond oxygen move in the opposite direction ? For photosynthesis plonts need

o toke in corbon dioxide, and o give out oxygen.

to:

Photosynthesis only tokes ploce in the

dim light carbon dioxide taken in for photosynthesis oxygen taken in for respiration

oxygen given out by photosynthesis

D -

light

.

oxygen given

outby photosynthesis carbon dioxide given out by respiration

dark

These goses poss into ond out of leoves through

oxygen taken in

the stomoto.

forrespiration

+

+

carbon dioxide given out by respiration

Experiment 12.15 Photosynthesis ond respiration Set up three boiling-tubes qs shown here: Put 5 cm3 of hydrogencqrbonote indicotor into eoch tube. Put o leof in tubes 1 ond 2 so thot eoch is supported by the wollof the tube. The underneqth of the leqf should foce inwords. Put leqf 1 in dorkness by covering the tube with tin foil. Leqve the tubes neor o light for 2 lo 3 hours. If corbon dioxide is odded to the oir, the hydrogencorbonote indicotor will turn yellow If corbon dioxide is used up from the oir, the hydrogencqrbonqte indicotor will turn purple

Look ot your results. o In which tube wos corbon dioxide releosed by the leof ? o In which tube wos corbon dioxide token up by the leof ? o Whot wos the purpose of tube 3 ?

During doylight plonts produce more oxygen by photosynthesis thon they use uP in resPirotion. At night plonts produce only corbon dioxide by respirotion.

792

2

tin foil

hydrogen carbonate indicator

3

leaf

)

Plont nutrients

Hove you seen bottles of 'plont food' for sole Whot do you think these contoin ?

? Thomes

Plonts need more thon corbon dioxide ond woter for heolthy growth. They olso need minerol solts or nutrients. These ore usuolly found in the soil. Nutrients ore token up in smoll omounts by the roots. Con you remember why plonts need nitrotes

?

They need the nitrogen to moke proteins. So nitrogen is one nutrient needed for growth. Mognesium is used to moke chlorophyll. Whot would leoves look like if mognesium wos locking in the soil? Leoves without enough mognesium look yellow. We soy the plont is deficient in mognesium. A shrub lacking magnesium

Experiment 12.16 The et'fects of nutrients on growth You con use woter cultures to find out why plonts need different nutrients. Set up some test-tubes os shown here:

seedling

Eoch solution locks o certoin nutrient except tube which hos oll of them.

1

normal culture

Leove the opporotus in good light for 6 weeks.

o Whot sort of things would you look for in the plonts ofter 6 weeks ? How obout colour ond size of leqves ? How obout length of stems qnd roots?

o

How would you meosure ony chonges

tin foil to keep out light

2 no calcium

3 no phosphates

4 no nitrates

5 distilled

water

?

o Why do you think the tubes were covered

with tin foil?

Does this stop other plonts growing in the woter?

Symptoms shorrn by plffits deficient in nutrients include: o Lock of nitrote-stunted grou/th ond yellow older leoves.

r o

Lock of phoephote - poor root growth ond purple younger leoues. Lock of potoseium-yellow leqves with deod spots.

193

)

Fertilisers

10

Whot hoppens if the soil does not contoin enough nutrients The former or gordener odds more os fertiliser. Fertilisers reploce the missing nutrients.

?

(U

.C 8

bo

E tr 6

o

E

The groph shows the yield of winter wheot with different omounts of nitrogen fertiliser:

Whot is the yield with no nitrogen fertiliser Whot omount of fertiliser would you use ?

NPK fertilisers contoin

o 4 '= 300

?

nitrogen top dressing (kq/ha)

:

o Nitrogen (N) for growth of leoves ond stems o Phosphorus (P) for heolthy roots o Potossium (K) for heolthy leoves ond flowers.

{'

Both phosphorus ond potossium help the reoctions in photosynthesis ond respirotion to work.

This fertiliser is colled 25 :0 :76. Whot does this meon ? ?

Chemicolor ortificiolfertilisers ore used in huge omounts. They ore eosy to store ond odd to the lond. The former knows exoctly how much of eoch nutrient there is in the fertiliser. The former hos to be very coreful obout how much fertiliser is used ond when. Roin con wosh fertiliser into rivers ond streoms where it couses woter pollution. (This is covered in Chopter 20.)

Noturol fertilisers include formyord mcnure ond composts. Some formers prefer these becouse they odd humus to the soil. Humus improves the structure of the soil. Noturol fertiliser rots down ond releoses nutrients more slowly. There is olso less threot to the environment. The problem for the former is thot the omount of eoch nutrient in the fertiliser is not known. Moke o toble of the odvontoges ond disodvontoges of noturol ond chemicol fertilisers.

794

n@

\

The proportions of nitrogen, phosphorus ond potossium (N:P:K) ore shown on the fertiliser bog.

Noturol or chemicol

o

+\- ,f

ryG

Hydroponics is the growth of plonts without soil. Most tomotoes, cucumbers ond sweet peppers ore grown this woy.

Peot culture Hove you seen tomotoes growing in gro-bogs ? This is known os peot culture. It is not used much by commerciol growers. Peot is ocid ond does not contoin mony nutrients. So the peot hos to be treoted before it con be used.

It is very populor with gordeners. But this hos meont digging up peot bogs ond domoging the environment.

Cucumbers grown in artificial media

Nutrient film technique Plonts grown using this technique ore supported in sterile sond or rockwool. A solution is circuloted to the roots of eoch plont. The solution hos: o oxygen bubbled through it-so the roots con respire o the correct type ond omounts of nutrients o the best pH for growth. It is eosy to olter the omounts ond types of minerol solts This willbe different for different crops ond for different stoges of development of the plonts. This technique hos been trioled by the Desert Development Centre in Egypt.

Tomatoes grown by n

utrient fi lm tech n ique

195

)

Biology ot work: Glosshouse production Growers try to improve the yield of their crops. They try to give them the best possible conditions for photosynthesis to toke ploce.

Conditions inside o glosshouse ollow plonts to: o grow eorlier in the yeor o grow in ploces where they would not normolly grow well. How ore these conditions provided

?

o Temperoture Sunlight heots up the inside of the glosshouse. The gloss stops o lot of this heot from escoping. Electric or poroffin heoters con be used in cold weother. Ventilotor flops con be opened to coolthe glosshouse if it gets too hot.

Ve

nti I ato

r f ap s op e rate autom ati cal ly I

o Light The gloss lets in sunlight. Artificiqllighting con be used to grow plonts when sunlight gets too low. Blinds con shode out very strong light.

o Corbon dioxide Growers con pump corbon dioxide into glosshouses to increose the rote of photosynthesis. Sometimes poroffin heoters ore used. These increose both the temperoture ond corbon dioxide becouse when poroffin burns it releoses corbon dioxide.

o Woter Mony glosshouses hove outomotic wotering systems. When needed, sprinklers ond humidifiers come on. Water misting of cabbages

Allthese foctors moy be controlled by computer Sensors ore used to detect eoch foctor. The feedbock is processed by the computer.

796

)

Growth in plonts

In onimols, cell division ond growth tokes ploce in oll ports of the body. In plonts, growth is restricted to porticulor growing regions. Cell division ond growth tokes ploce moinly ot the root tips ond the shoot tips.

How con we estimote plont growth ? Wellyou could meosure root length or plont height. You could olso use o quodrot to estimote the oreo covered by the plont. If you horvest the plont moteriolwithin the quodrot, heot it in on oven to drive off the woter, then you hove o meosure of the dry weight of the somple (see poge 288).

Control of growth If you cut off o shoot tip the shoot stops growing. But if you put the shoot tip bock on it storts to grow ogoin. The shoot tip mokes o hormone cqlled ouxin. The ouxin stimulotes the shoot to grow. The ouxin couses the cells to elongote.

ffi shoot tip cut off growth stops

Plonts respond to things like light, grovity ond woter, Ports of the plont either grow towords them or owoy from them. These slow growth responses ore colled tropisms.

shoot tip cut off and replaced growth continues :

How light offects growth Look ot the photogroph of the cress seedlings: They hove been put in o window for some time The shoots hove grown towords the light.

How is this controlled

?

o

When o shoot only gets light from one side most ouxin is found on the shoded side.

o

The ouxin mokes the shoot grow more on the shoded side.

o

The shoot bends towords the light.

This sort of response is cqlled o phototropism Becouse shoots grow tourords the light we soy

thot they ore positively phototropic.

Whqt is the odvontoge to the shoot of growing towords the light ?

auxin made by shoot tip

auxln passes down shaded side

+

+

auxin makes cells elongate more on shaded side

+

light

light

shoot bends towards the light

797

How grovity offects growth shoot grows upwards

Why is it thot whichever woy o seed is plonted, the root olwoys grows down ond the shoot olwoys grows up ?

t

I

The stimulus in this cose is grovity. Shoots grow up, owoy from grovity. Roots grow down, towords grovity. Agoin ouxin controls this growth.

root grows downwards

If o plont is put on its side the ouxin builds up on the lower side of the shoot ond root.

o

In the shoot the ouxin stimulotes it to grow more on the lower side.

auxin made by root tip

G

o This couses the shoot to bend upwords. o In the root the ouxin olso builds up o

s,",itvl "Jilli:li'#

on the lower side. But ouxin slours down growth in o root. So the upper side of the root grows quicker thon the lower side.

cells elongate more on upper side

o The root bends downwords. gravity

A growth response to grovity is colled o geotropism Exploin why we soy thot o roots ore positively geotropic, ond o shoots ore negotively geotropic. Whot is the odvontoge to the plont of its shoot growing owoy from grovip ond its root growing towords grovity

?

Auxin olso hos other effects on plont growth. As it posses bock from the tip of o stem, ouxin prevents side-shoots forming. Whot do you think would hoppen if the tip of the stem wos removed ? The ouxin will no longer be mode so the side-shoots stort to grow. Why does hedge clipping produce o much bushier hedge

198

?

t

auxin causes cells to elongate less on lower side

)

Biology ot work: Plont hormones Rooting powder contoins synthetic ouxins. A cutting is dipped into the rooting powder. The powder stimulotes the cut shoot to grow roots Cornotions ond chrysonthemums ore grown in this woy.

Synthetic ouxins ore olso used os selective

weed-killers. They killthe weed by moking it grow too fost. The ouxins ore sproyed on the leoves, so brood-leoved weeds ore offected. Norrow-leoves grosses ond cereols ore not offected.

Auxins controlripening by telling the ovory to develop into o fruit. They ore normolly mode by the developing embryo. Some growers sproy synthetic ouxins on unpollinoted flowers of tomoto plonts ond peor trees. Fruits form without fertilisotion. So these fruits hove no pips !

Hove you ever eolen seedless gropes or seedless sotsumos ?

These hove been grown with the help of

synthetic plont hormones.

Plont hormones con olso be used to regulote the ripening of fruit during tronsport.

Ethene

is mode by mony fruits. It couses the fruit to ripen. Bononos ore picked when they ore unripe ond tronsported in ships. During storoge ethene is used to moke them ripen So when they orrive for sole they hove chonged from green to yellow !

199

Summory o

Green plonts use sunlight to mqke food by photosynthesis. Chlorophyll inside chloroplosts is used to obsorb the light. Corbon dioxide ond woter ore needed for photosynthesis. Sugors ore produced in photosynthesis ond cqn form other corbohydrotes, omino ocids, proteins ond fots. Oxygen is releqsed os o woste product during the process.

o

Plqnts ore importont for food, medicines, hqbitots ond controlling the omounts of corbon dioxide ond oxygen in the qir.

o

The rote of photosynthesis con be limited by light intensity, corbon diodde ond temperofure

)

Leoves qre well odopted for obsorbing light

ond gos exchonge.

o

Stomoto control exchonge of goses ond woter loss.

o

Photosynthesis tokes ploce in light but respirotion occurs oll the time.

o

Minerol solts ore importont for heolthy plont growth.

o

Plont growth ond development is controlled by hormones. These hormones con be used commerciolly to produce seedless fruit, to oct qs o rooting powder ond os selective weed-killers.

3. Three geronium plonts were kept

Questions

1. Copy ond complete

o

in the dork for

24 hours. :

Eoch wos then covered with o bell-jor A, B ond C.

Green plonts moke their own food by . . . . . Green . . . . in the chloroplosts of the leoves trops the sun's . . . Row moteriols for this process ore corbon. . . . ond. . . . . Sugors ore mode in the leoves ond ore soon chonged to . . . . . The woste product of this process is the gos . . . . .

The opporotus wos left in the light for 5 hours os shown here:

.

A

2. The

B

C

black polythene bag

soda

groph shows the effect of increosing the omount of corbon dioxide on the rote of photosynthesis of o pond weed.

o) Why were the three plonts left in the dork

before the stort of the experiment ? b) Whot wos the sodo lime for in bell-jor A ? c) Why wos block polythene put over bell-jor C? d) After 5 hours o leof from eoch plont wos

.o

a o

!-

co >,o o>

OE co oo. oo

tested for storch. Whot colour would eoch leof go with iodine? Try to exploin eoch of the results.

q)

(E

4.

amount of carbon dioxide

o) Whot other conditions must be kept

constont if this is to be q foir test ? b) How do you think the omount of corbon dioxide wos increosed ? c) Why did the groph increose to begin with d)Why do you think the groph levels off ? 200

?

Lettuces con be grown in tunnels mode with cleor polythene. o) Give two reosons why cleor polythene increoses the yield of lettuces. b)Why do the tunnels not need to be moved to woter the plonts ? c) Why is corbon dioxide odded to the oir in the tunnels ?

5.

The opporotus wos used to collect the gos releosed by woter plont:

7.

o) Nome the ports of the leof lobelled A to G B

gas

O

water containing carbon dioxide

o

o o

plasticine support

Distance from lamp (cm)

O

6

60 40 30 20

10 18

24 25

) Why wos o piece of thick gloss ploced between the lomp ond the plont?

To find out if photosynthesis hos token ploce in o leof we con corry out o test. Copy out the stoges listed on the left in the

correct order. Motch eoch one with the correct reoson on the right.

test

woter boilthe leof in ethonol cover the leof with iodine wosh the leof in cold

dip the leof in boiling

woter

Reason to test for storch

to soften it to remove the ethonol to extroct the chlorophyll

O

FE b) Motch eoch lobelwith one of these functions : i) Conies woter ond minerolsolts to the leof. ii) Prevents too much woter loss from the upper surfoce. iii) Opens to ollow goses to poss into ond out of the leof. iv) Most photosynthesis tokes ploce here. v) Goses from here poss into the spongy

Number of bubbles per minute

100

Stage in

c D

d) Plot these results os o line-groph. e) Try to exploin ony pottern thot you find in the results.

6.

{

/t A /8

o) How could you test the gos for oxygen ? b)Why is the gos collected in the test-tube not pure oxygen ? c) Why wos the woter enriched with corbon dioxide ? A lomp wos ploced ot different distonces from the woter plont. The number of bubbles releosed per minute wos recorded:

f

plasts

I

water plant

ro

I

G

cells.

vi) Light is oble to poss stroight through this loyer. vii) These cells contoin most chloroplosts.

8.

The rote of photosynthesis of o tree wos recorded for 36 hours. high a '6 (D A-C

o> l:o soo6

a.m. 6 p.m. 6 a.m.

6 p.m.

midday midnight midday

Use the groph to onswer these questions. o) When wos the rote of photosynthesis highest ? b)When would most corbon dioxide be releosed into the oir?

c) When would most oxygen be releosed into the oir ?

Further questions on poge 211 207

chapter 73

A tronsport system Most living things need o tronsport system. Their bodies ore too lorge for moteriols to simply diffuse in ond out. Only very smoll orgonisms con corry things oround their body by diffusion. They hove o lorge surfoce oreo to volume rotio ond o short diffusion pothwoy. So it is eosy for moteriols to diffuse in ond out.

Whot things do cells need to stoy olive Whot do they need to get rid of ?

?

Our tronsport system is the blood. It brings food ond oxygen to our cells. It removes corbon dioxide ond woste chemicols Plonts hove o tronsport system too. They hove lots of thin tubes inside them. These corry liquids up ond down the stem ond olloround the plont.

"General Sherman" redwood tree uptake of water in xylem transport ol food in phloem

+ +

bud

Some tubes ore colled xylem (sigh-lem). They corry woter ond minerol solts. The roots toke in the woter ond dissolved solts. These poss up the stem in the xylem to the leoves. Some tubes ore colled phloem (flow-em). They corry dissolved food like sugors ond omino ocids which ore mode in the leoves by photosynthesis. The phloem corries the food to every port of the plont. The phloem olso corries hormones oround the plont. These hormones control cell division for growth of the stem, roots ond leoves. Hormones olso control the growth of flowers ond fruits.

202

sunlight energy carbon dioxide

sugar made by photosynthesis

water and minerals from the soil

sugar moves down to growing root or up to growing bud

Inside the root To find the tronsport tissue of o root we need to slice it open ond look inside. The diogrom shows whot o root tip looks

like under the microscope:

root hairs take in water and mineral salts phloem brings food from the leaves which is used to make new cells at the root tip

cortex stores some food as starch xylem carries water and mineral salts up the stem

root cap protects the root tip as it grows through the soil

root tip grows as the cells divide

Section through a young root. Notice the many root hairs.

Inside the stem We con find out whot is inside o stem by cutting o thin slice ond looking of it under o microscope

cambium cells make new xylem and new phloem as the plant grows

a vascular bundle is made up of phloem, cambium and xylem cortex

epidermis is a single

pith

layer of cells on the outside of the stem which protects the stem and cuts down water loss

phloem carries dissolved food and hormones around the plant xylem carries water and mineral salts up to the leaves

Section through a young stem

Experiment 13.7 Water transport in the xylem Stond some celery in woter contoining q blue sharp scalpel dye for o few hours. Corefully cut off o length of obout 2 cm. Look of the cut end. Con you see where the dye is? The dye hos been corried up the xylem tubes.

A

Corefully cut out o?cm length of xylem. Put it onto o slide with q cover-slip. Look of it under the microscope.

203

The roots onchor the plont in the soil. Another importont role of the roots is to toke up woter ond minerolsolts. Just behind the root tip ore microscopic hoirs. These ore colled root hqirs. Woter posses into the root hoirs by osmosis. Do you remember whot hoppens in osmosis ?

The woter in the soil hos o weok solution of soil

solts.

particle

The cell sop in the root hoir cell hos o stronger solution. Woter posses from the soil into the root hoir cellby

soil water

xylem vessel

AB

osmosis.

fifi0

The woter hos diluted the cellsop in the root hoir cell. The root hoir cell now hos o weoker cell sop

)

root hair

thon cellA. Woter posses from the root hoir cell into cellA by osmosis.

cells of coftex

water passes up the stem in the xylem The pathway of water across a root

The woter hos diluted the cellsop in cellA. CellA now hqs o weoker cell sop thon cell B. So woter posses from cellA into cell B by osmosis.

This continues ocross the whole of the root cortex.

Woter eventuolly reoches the xylem. Woter is corried up the xylem to the leoves.

Experiment 73.2 Looking at root hairs Look closely of o section of o young root under the microscope.

Look ot the root hoirs.

o

r

Whot is their shope like ? How does their shope help them to toke in woter

Root hoirs ore long ond thin. They hove o lorge surfoce oreo through which woter ond minerol solts con enter.

2M

?

)

Tionspirotion

Woter is pulled up the xylem in the stem from the roots to the leoves. The woter is used for photosynthesis ond to stop the plont from wilting. Woter evoporotes from the leoves into the oir. This is colled tronspirotion.

leaf cells

water is lost through the stomata

xylem vessels in stem

As woter is used up or lost from the leoves, more is sucked up from the xylem vessels. It's o bit like sucking woter up o strow. So there is o continuous flow of woter from the roots to the leoves.

This movement of woter up the xylem is colled the tronspirotion streom.

Experiment 73.3 To demonstrate transpiration You con prove tronspirotion tokes ploce by setting up the opporotus shown here: Mork cleorly the level of the woter in eoch flqsk. Weigh eoch flosk. Now leqve the opporofus for 24 hours.

o o

Hos the level dropped in flosk

A? \trhy

A

B

oil

water

hos it?

Is flosk A now lighter? Why is this? balance

balance

More obout tronspirotion o Woter first evoporotes from the spongy cells into the oir spoces.

o The oir spoces become full of woter vopour. o Woter vopour diffuses through the stomoto into o

the oir. The woter lost from the spongy cells is reploced by more woter from the xylem.

Experiment

73,4

Comparing water loss t'rom each side of a leaf Cobqlt chloride poper is blue when dry ond goes pink when it comes into contoct with woter. Put o piece of cobolt chloride pqper on eqch side of o leof. Keep the poper in ploce with two slides ond elostic bonds. See on which side the pqper turns pink first. o Will it be the side with most stomoto?

arr space

xylem vessel

t^--SL ---l

^^)

@

"--

water evaporates off cell wall

7^-r4>\ ry-

0

water vapour

stoma

Troncplrction is the loss of woter vopour from the surfoce ol leqres.

205

)

Foctors qffecting tronspirotion

Scanning electron micrograph of open stoma

More tronspirotion tokes ploce during the doy thon ot night. This is becouse the stomoto ore open during the doy ond close ot night. The stomoto moy olso close in very dry conditions This is becouse the woter lost in tronspirotion is not being reploced by woter from the soil. The stomoto close to reduce tronspirotion. If the plont still does not get enough woter it will stort to witt. Its cells hove lost so much woter thot they ore no longer turgid or full of woter. Turgid cells ore firm ond give the plont support. If the cells become floccid then the plont becomes soft. The stem is no longer upright ond the leoves droop.

Experiment 73.5 Stomata and water loss Set up four leoves os shown here: Vqseline will block the stomoto ond slow down honspirotion. Look of the leoves qfter o few doys. o Which do you think hos lost most woter ? Other foctors offecting tronspirotion ore environmentol. Look of the grophs:

o Windy conditions

vaseline on upper and lower surface

on only

lower

surface

increose the rote of tronspirotion.

o Humid

c

E

'o-

'o-

@

o

c(E

o

o o g

o (6

c(U

(U

conditions decreose the rote of tronspirotion. The oir contoins o lot of woter olreody.

no vaseline on upper surface vaseline only

c o

Woter molecules ore blown owoy from the leof surfoce, so more diffuse out of the stomoto.

r

four identical privet leaves

081624

25

wind velocity (km/h)

Worm conditions increose the rote of honspirotion. The oir con hold more woter vopour.

50 75

humidity %

c .E (U

'a o

o Light couses the stomoto to open.

C

(!

This increoses the rote of tronspirotion.

o o 6

It's o bit like woshing on o line. Whot conditions dry the clothes quickest ? Whot conditions dry the clothes more slowly

206

10 15 20 ?

temperature (oC)

25

100

)

Meosuring tronspirotion

It is not eosy to meosure the rote of tronspirotion. But you con use o potometer to meosure the rote of woter uptoke. The omount oi woter lost is octuolly less thon the omount of woter token in by the roots. This is becouse some of the woter is used up in photosynthesis.

Experiment 73.6 Measuringthe rate of water uptake Fillo copillory tube by submerging it in woter. Cut the end of o shoot under the woter. sharp Attoch it to the copillory tube with o piece cutting of rubber tubing. instruments Toke the copillory tube out of the woter. Clomp the opporotus in the position shown. See how for the bubble trovels olong the tube in 5 minutes.

A

Now try it with o fon neor the potometer. o Does the rote increose ? Why is this ? Now hy putting o polythene bog over the shoot. This mokes conditions humid. o Does the rote decreqse ? Why is this ? o Would o blqck plostic bog moke the rote decreose even more ? Why do you think this is?

slanting cut

water evaporating

bubble moves along as water moves up to the leaves plastic tubing ruler

cut shoot

Here is o more occurote potometer. It works in the some woy. Voseline is put on the rubber bung. Whot do you think the reservoir is for? How could you get the oir bubble bock to the beginning of the scole ?

reservorr tube air bubble

Inuestigation 73.7 Plan an inuestigation on the rate of transpiration You could use weight loss ond woter intoke os o meosure of the rote. You could look ot the effech of different voriobles on different plonts. You could investigote how different numbers of stomoto offect the rote. Check your plon with your teocher before you stort.

207

)

Minerol solts

Plqnts need minerol solts or nutrients. For instonce, nitrotes ore needed to moke proteins There is only o weok solution of these solts in the woter in the soil. Often solts ore token up even though there ore less in the soilthon there ore in the root. These solts connot enter the root by diffusion.

Why not? The solts ore token up by octive tronsport. Active tronsport con collect solts ogoinst o concentrotion grodient. This needs energy from respirotion.

Scanning electron micrograph of xylem vesse/s. Note the thick bands that support the vessels.

Agoin the root hoirs give o lorge surfoce oreo for

toking up minerol solts. There ore mony oir spoces in the soil. Oxygen posses from this oir into the root hoir too. Minerolsolts ore corried up to the leoves with woter in the xylem vessels.

)

Active tronsport is the uptoke of molecules or ions, ogoinst o concentrotion grcdient, using energy from respircrtion.

Tlonsporting food

Food is mode in the leoves by photosynthesis. The soluble products ore sugors, omino ocids ond

fotty ocids. These ore corried to oll ports of the plont in solution in the phloem. This is often colled tronslocotion. Xylem ore deod tubes but phloem is liuing tissue. Movement of substonces in the phloem is thought to involve octive tronsport. The plont cells hove to use energy to move the dissolved substonces olong. Where does the food end up

o

?

Sugors ore chonged to storch ond stored

in the root cortex ond in seeds. Sugors olso form cellulose for new cell wolls ot the growing root tip ond shoot tip. Sugors ore olso tronsported to the fruits.

o Amino ocids moke proteins needed to moke new cells o Fotty ocids form fots thot ore stored in mony seeds. 208

Photomicrograph of phloem vessels

)

Biology of work: Monocultures qnd crop rototions Monocultures A monoculture is growing the some crop on the some lond, yeor ofter yeor. The moin benefit of monocultures is on economic one : o Increosed use of mochinery ond decreosed lobour costs meons thot continuous cropping of one crop brings greoter economic returns per unit oreo of lond. o However, monocultures require the use of lots more fertilisers ond pesticides to mointoin high yields.

o

The use of chemicol fertilisers does not improve the structure of the soil, unlike orgonic fertilisers which rot down ond provide the soilwith humus os well os nutrients.

o

The pH of the soil moy need to be corefully reguloted to meet the needs of the crop. First the soil pH is tested, ond then lime is odded if the soil is too ocid or peot if it is too olkoline.

o

Monocultures olso provide lorge oreos thot con become infested with pests ond diseoses, which hove to be controlled. Aphids con spreod diseqses such os tobocco mosoic virus. Aphids feed on the sop in the phloem tubes in crop stems.

antenna compound eye

They use speciol mouthports colled stylets to penetrote the phloem. The viruses enter the phloem in the solivo of the insect ond multiply. Aphids ore the moin vectors (tronsmitters) of viruses between plonts

stylet

Crop rototions The use of inorgonic fertilisers qnd monocultures hos led to the loss of the troditionol crop rototions.

Crop rototion influences the omounts of nutrients thot need to be odded to grow different crops. For exomple, winter wheot grown ofter onother cereol needs for more nutrients thon if it is grown ofter o root crop This is becouse o root crop, like pototo, tokes up for less nutrients thon o cereol crop. Growing o plonned sequence of crops hos been proctised for mony yeors.The Norfolk four-yeor rototion uses o ley. This is o gross/ legume mix thot cqn be grozed by livestock. Legumes (the peo fomily) increose the omount of nitrogen in the soil ond so increose its fertility (see poge 314). Different crops need different methods of cultivotion, which leods to on improvement in soiltexture. Also, growing different crops breoks the cycle of crop pests. So there is less chonce of o crop pest or diseose getting o grip thon in the cose of growing monocultures.

Year

Year 4

1

I

Year 2

Year 3

+

The Norfolk four-year rotation

209

Summory o

o

)

Plonts hove o honsport system mode up of tubes colled xylem ond phloem. Xylem corries woter ond minerol solts from the roots up the stem to the leoves. Phloem cqrries dissolved food from the leoves to oll ports of the plont. The phloem olso tronsports hormones qround the plont.

o Minerolsolts qre token up by octive tronsport. o Leoves lose woter to the oir by tronspirotion.

Woter posses into the root hoirs from the soil woter by osmosis.

o

Questions

3. Copy ond complete: Woterposses into oroot. . . . by . . . . . Minerol . . . . ore token upby. . . . tronsport. Aroot hoirhos o. . . . surfoce . . . . fortokingup

1. Look

ot the diogrom of the root hoir in the soil

AB

t_.1

Tronspirotion streom qllows woter to hovel from the roots up the stem to the leqves. Tronspirotion is controlled by the opening ond closing of stomoto. Environmentql foctors like wind, humidity ond temperoture cqn offect tronspirotion. The soft ports of o plont ore supported by

turgid cells.

woter ond minerol solts. Woter is lost from the leoves by . . . . . This is controlled by the opening ond closing of the . . . . . Dissolved. . . . ond hormones ore corried to oll ports of the plont in the . . . .

C

.

4.

F

o) Nome the ports lobelled A to G. b) Exploin how woter gets into the root hoir from the soil. c) Give two other functions of o root hoir.

2.

The groph shows the rote of tronspirotion ond the rote of wqter uptoke in smoll pine tree : 30

I

transpiration

920 6 = o

water uptake

5ro o E

(d

o 124 8124 noon 1st March

midnight

8 12

time of day noon 2nd March

o) Compore the rote of tronspirotion with the rote of woter uptoke i) during the doy ii) during the night b) Stote the dote ond the time when the rote of tronspirotion wos highest.

21.0

A potometer wos used to meosure woter uptoke by o leofy shoot. Time taken for the water to move 100 mm

Conditions

(minutes)

cool, moving air, in daylight cool, still air, in daylight warm, moving air, in daylight warm, still air, in daylight warm, still air, at night

2 6 1

3

60

o) From the toble, stote three conditions which offect the rote of woter movement through the plont. b) In cool, moving oir, in doylight, work out the rote of woter movement in mm per minute. c) Give two woys in which the oir oround the shoot would be offected if it wos covered with o tronsporent plostic bog. d) Give two reosons why loss of woter from the leoves is importont to o plont.

Further questions on poge 211.

Further questions on Plonts os orgonisms

)

Feeding in plonts

1.

q) Why did she cover port

of the leof with oluminium foil? t1l b) The student left the plont in bright sunlight for 4 hours. aluminium Then she took the leof off foil the plont, removed the foil, qnd tested the leqf for storch. i) Nome the solution which is used to test for t1l ii) The diogrom shows the leof ofter the

Leoves ore orgons of photosynthesis. They come in oll shopes qnd sizes but oll of them qre odopted to obsorb os much light os possible. o) Give one woy in which leoves ore odopted

to obsorb light. tll b) The diogrom shows o cross-section through o leof. light

storch.

\ cuticle

\

storch test.

Whot colour would ports X ondZ go ofter the test? t2l c) Write o conclusion for the student's

experiment.

palisade layer

3. spongy layer

t1l

z

(AOA)

The groph shows the omount of sugor contoined in the leoves of o group of plonts in o glosshouse over o period of o week.

I

to) Ee cL'F =^c3

4

:E air

space

E f (E0 2 =cd tro_ (! 0.=

stomata

Exploin the following observotions : i) The cuticle is tronsporent. t1l ii) Most chloroplosts ore found in the polisode loyer. t1l iii) Air spoces ore found mostly in the spongy loyer. tll c) Whot is the substonce in chloroplosts which obsorbs light ? tt l d) Exploin how eoch of the following offects the rote of photosynthesis in o potted plont. i) Moving it neorer to the window. t1l ii) Moving it to o colder room. tll (ocR)

2. A student wos osked to find

if plonts need light to moke storch. She wos given o potted plont which hod been kept in o dork cupboord for 48 hours. She covered port of the leof with oluminium foil os shown in the diogrom which follows.

0

0't234567 day

o)

i)

Copy ond complete the word equotion to show how sugor is produced:

ii) b)

i)

sunlight

.... ---

t2l

equotion.

t1l

.... +

,->- sugor + oxygen chlorophyll Nome the process shown by the

Exploin the rise ond fqll in the sugor leveleoch doy. t2l ii) Suggest o reoson for the overoll increose in the omount of sugor present eoch doy. tll iii) Suggest o reoson for the lower peok on doy 5. tll c) Suggest turo reosons why putting o gos fire in the glosshouse might increose the omount of sugor produced. t2l (EDEX)

Note: although a queslion may be marked (OCR) etc,

it will often be relevant to other examinations as

well. 271

Further questions on Plonts os orgonisms

4.

c) The rote of photosynthesis moy be offected by foctors other thqn corbon dioxide concentrotion. Give two of these foctors. [2/ d)Some crops ore grown in glosshouses. Give two odvontoges of growing crops in

Plonts convert light energy into chemicol energy during photosynthesis. The groph shows the effect of light intensity on the rote of photosynthesis.

glosshouses.

,9

o o

6.

-c

c

+O

oo oo

i) ii)

minerolsolts.

b)A former wonts to increose his yield by

Exploin the relotionship between light intensity ond the rote of

photosynthesis.

20

t2l

18

Suggest one other vorioble thot offects

the rote of photosynthesis. t1l Sketch o curve to show how this vorioble would offect the rote of photosynthesis (put the vorioble on the horizontol oxis ond the rote of photosynthesis on the verticol oxis). [7J b) Glucose is mode by photosynthesis. Whqt con the plont use the glucose for ? tll

iii)

(EDEX)

t2l

sensible use of fertilisers. The groph shows how the moss of crop produced from o field depends on the quontity of nitrogen used.

light intensity

o)

(AOA)

q) Plonts need minerolsqlts for heolthy growth. Give the chemicol nomes of two

ppes of

E-o-

t2l

16 ah

o 14 c

c o

.c

't2

oo

o 10

ofo o

8

o

6

o-

o

4

5. The toble

below shows the results of on investigotion to find the effect of corbon dioxide concentrotion on the rote of photosynthesis. Concentration of carbon dioxide in air (%)

Rate of photosynthesis

(arbitrary units) 0

0 0.2 o.4 0.6 0.8

35 70 105

1.0

120

1.2

't20

1.4

120

115

o) Drow o line groph of these results on q sheet of groph t2l b) Use the groph to describe the effect of corbon dioxide concentrotion on the rote of t2l

poper.

photosynthesis.

212

2

100 200 300 400 500 600 700 800 900 1000 amount of nitrogen fertiliser in kilograms

Whot is the mqximum moss of crop thot could be produced by using nitrogen fertilisers on the field ? tll c) Mony of the chemicqls in fertilisers dissolve in woter. When it roins, some of the fertiliser is woshed out of the soil into rivers ond streoms. Whot effect does the fertiliser in the river woter hove on the river plonts: i) Immediotely or in the short term; t1l ii) In the long-term? tll d)Some people prefer to eot brgonicolly grown' food. This is food which hos been grown without the use of sYnthetic fertilisers, pesticides or weed-killers. Excluding cost, describe two odvontoges ond two disqdvontoges of eoting brgonicolly grown food. t4l (AOA)

Further questions on Plqnts os orgonisms

7.

o) Copy the toble ond motch eoch letter to the description of its function. tsl

The diogrom shows o plont leof during photosynthesis. water

roots

light

transports sugar absorbs light produces pressure inside cells carries water from the stem to the leaf allows water to leave by evaporation

gas X

b)The omount of corbon dioxide in the oir oround q crop of wheot wos meqsured during two different doys, X qnd Y. The results were plotted os the following

gas Y

o)Nome:

i)

gos

X

ii) sqs Y

groph.

t2l

b)Nome the tissue which tronsports: i) woter into the leoves ii) sugors out of the leoves c) Why is sunlight necessory for photosynthesis

o

1,

t2l

xo =o o f

c z. (E

oo .= (u

?

t1l

d) Some of the sugors produced by photosynthesis ore stored qs storch in the roots. Exploin, os firlly os you con, why it is on odvontoge to the plont to store corbohydrote os storch rother thon os (AOA)

o o o

(E

.I

'6

E

(d

0.00

06.00

12.O0

18.00

24.OO

time of day

sugor. t3l

8.

Description of its function

Letter

sugars (to rest of plant)

i) Whot process wqs responsible for the drop in corbon dioxide ? [1] ii) Suggest why there is o difference between the grophs for X ond Y. tll c) At whot time did the wheqt plonts give out most oxygen ? t1l

The diogrom shows o section through o green leof.

d)Nome two substonces found in the soil which could help the growth of the

wheqt.

t2l

(WJEC)

xylem

) C phloem

E

) 9.

\D

Plont tronsport o) Plonts lose wqter through their leoves. i) Whot nqme is given to the loss of woter from the leoves? t1l ii) Whot nome is given to the pores through which this woter is lost? t1l iii) Exploin why the movement of wqter through plonts is importont to them. /3J 2L3

Further questions on Plonts os orgonisms b) The loss of woter from q leofu shoot con be

shown using o potometer. A potometer is shown in the diogrom. As woter is lost from the leof the bubble slowly moves olong the scole from left to right.

c) Much of the woter going into the root hos to get to the leoves. Exploin how woter trovels upwords through the stem to the

leqves.

t3l

(AoA)

11. The diogrom shows three plont stems, A, B ond C, of the stort ond end of on experiment.

ABC opaque

leafy shoot

opaque

cap reservot

water capillary tube tap

bubble

scale

Whqt willbe the effect on the movement of the bubble of : i) increosing the temperoture of the oir oround the leofy shoot; t1l ii) increosing the humidip of the oir oround the leofy shoot; t1l iii) opening the reservoir top ? t1l c) Plonts which live in dry desert-like oreos often hove leoves which ore modified to form shorp spines or prickles. Stqte two woys thot these modified leoves help the plont to survive in the desert. 12J (AOA)

L0. The roots of o green plont oct os o link between the plont ond the woter in the soil. o) For which life process does the green

plont need wqter qs o row moteriol? t1l b)The drowing shows o sectionolview of q root hoir on o root in some soil. particles of soil cells of the root

start

light

light

€

€

end

start

€

end

start end

o) Whot does this experiment suggest obout which region of o plont stem is sensitive to the stimulus of light? Give reosons for

your onswer. [3] b) Exploin whot couses the plont stem to bend towords the light. t3l c) Suggest how this response is beneficiolto

plonts.

t2l

(oCR)

12. The tqble shows the height in mm, of two peo seedlings during the first 8 doys ofter

germinotion. Days after germination

1

2

3

4

5

6

7

0

2.5

6.0

14.0

24.0

32.0

44.0

62.0

0

1.5

4.0

10.0

16.0

20.0

36.0

58.0

0

2.0

5.0

12.0

Seedling P heighUmm

Seedling Q heighUmm

Mean seedling heighUmm

o) Whot wos the height of seedling P on

3? height? doy

b)On whot doy wos seedling Q 20mm in

root hair

Describe, in detoil, how the woter posses from the soil into the root hqir. t4l 214

light

water

tll ttl

c) Work out the meon height of the seedlings P ond Q, for eoch of the lost four doys. [4J d)On q sheet of groph poper, plot meon height of peo seedlings ogoinst time. Join

up the points you hove plotted with stroight lines. t4l (oCR)

chapter 74 Reproduction meons producing new living things. Animols ond plonts reproduce to mqke new individuols of the some species. Whot would hoppen if living things didn't reproduce ? There ore two moin woys of reproducing o osexuol reproduction, ond

o sexuol reproduction.

)

Asexuol reproduction

In osexuol reproduction there is only one porent. Allthe offspring ore identical to the porent. They hove exoctly the some genes. They ore colled clones. This saxifrage

makes lots of little plantlets. They become detached to make new plants.

Microscopic organisms like Amoeba are made of one cell. They reproduce asexually by

the cell dividing into two.

The potato plant makes potato tubers. These separate and form new plants.

Yeast also divides to make new cells. Each cell separates to form a new

individual.

In ollthese plontsond onimols ollthe offspring produced hove come from one porent.

Hydra is a freshwater animal made up of many cells. It grows little buds on

the parent's body. They separate and each

one grows into a new animal.

215

)

Sexuol reproduction

In sexuol reproduction there ore two porents. The porents hove sex orgons. The sex orgons moke sex cells or gometes. In mole onimols the sex cells ore colled sperm. The sperm ore mode in sex orgons colled testes (testis is the singulor of testes). In femole onimols the sex cells ore colled eggs. The eggs ore mode in sex orgqns colled ovories

Barnacles mating

During sexuolreproduction the sperm ond the egg join together. This is colled fertilisotion. A fertilised egg or zygote is produced. The fertilised egg divides mony times to form

A fertilised human egg

o boll of cells.

Soon it willgrow into on embryo. Eventuolly it develops into o seporote individuol.

Sexuol reproduction involves the Joining together of mole ond femole gometes (sex cells).

Getting it together The sperm contoins genes from the fother. The egg contoins genes from the mother. The fertilised egg hos o mixture of genes from both porents. So sexuol reproduction brings obout greoter in the offspring.

voriotion

The offcpring of sexuol reproduction show much mor€ vciction l*ror ttrose of qsexual

reproduction. Fertilisotion con toke ploce oufside the body This is colled externol fertilisotion.

-

in woter.

Con you nome some onimols thot reproduce like this ? In mommols, birds ond reptiles the sperm ond the egg join inside the body of the femole. This is colled

internol fertilisotion.

Con you nome some onimols thot reproduce like this ?

276

fertilised egg

ball of cells

Sex cells cell membrane

A sperm is o speciol cell thot con swim. It is designed to corry genetic informotion from the mole porent to the egg of the femole porent. The genes from the fother ore corried in the nucleus of the sperm.

head

rane cytoplasm

An egg is much bigger thon o sperm. It contoins yolk os o food store. It olso hos o nucleus. The genes from the mother ore corried in the nucleus of the egg.

Fertilisotion hoppens when the nucleus of the sperm joins up with the nucleus of the egg.

nucleus containing chromo-

middle prece

SOMES

jelly coat nucleus containing chromosomes

+--

Sperm on the same scale O

the tail beats like a whip and drives the sperm forward

How mony differences con you think of between eggs ond sperm ? Sperm

Eggs

small

large

swim using a tail

can not move much

no food store

have a food store

millions produced

much fewer made

s

Also the sperm cell hos mony mitochondrio to provide energy. Whot is the energy needed for ? The ocrosome is port of the sperm's heod. It releoses enzymes to digest o woy through the egg membrone. In whot woys ore eggs ond sperm similor

?

Mony eggs Animols like this fish hove externolfertilisotion. The sperm ond the eggs join together in the woter. These fish produce millions of eggs ond billions of sperm. Why do you think this is ? Whot might eot the eggs ? Whot might wosh the eggs ond sperm owoy

?

Inside o womon only one egg is usuolly produced ot o time.

The egg is protected inside the womon's body.

2r7

Plqnt tissue culture is o method of cloning plonts. Cloning results in the production of lorge numbers of geneticolly identicol plonts. These ore grown under sterile conditions in o suitoble growth medium (usuolly ogor jelly). o Firstly o porent plont with the desired chorocteristics

o o

1. A plant with

2. The stem is cut

into pieces, each with a bud

desired characteristics is selected

1"

+il

3. Each explant is sterilised in bleach solution

+

is selected.

Smoll pieces of tissue ore then cut off the plont. These ore then sterilised (usuolly in bleoch)

/ q. una., ,t",,t.

L

v

conditions the

explants are without horming the cells. trans{erred to { jelly in o o The tissue is then trqnsferred to sterile ogor agar (containing nutrients and culture bottle. --hormones) fungus -------->

Detritivore food choin

beetle -

/

frog

new decomposer material

:

deod onimol --------> blowfly moggots --------> blockbird --------> sporrowhowk

'::

'::

i:,r,::i::'ai

312

respiration

I

release of carbon dioxide

cycling

\nutrients returned to soil

)

The cqrbon cycle

All living things need corbon. It is used to moke corbohydrotes, proteins, fots, ond other importont molecules. These molecules moke up living orgonisms.

carbon dioxide in air photosynthesis

The corbon comes from corbon dioxide in the oir. Plonts use it in photosynthesis to moke food. Animols get the corbon by eoting plonts.

carbon compounds in animals respiration and decay

How does corbon dioxide get bock into the oir ? o Plonts ond onimols use some of their food for respirotion, releosing energy ond corbon dioxide. o Decomposers use deod plonts ond onimols for food. They use some of the decoying moteriol for respirotion, releosing energy ond corbon dioxide. o Fossilfuels like oil, peot, cool, ond gos contoin corbon. When they ore burned, corbon dioxide is releosed into the oir. These processes put corbon dioxide bock into the oir os fost os plonts remove it by photosynthesis. So the omount of corbon dioxide in the oir should stoy the some.

leeding

carbon compounds in plants rning

formed millions of years ago from dead vegetation fossil fuels - oil, coal, peat, gas

Con you see thot two processes dominote the corbon cycle These ore photosynthesis ond respirotion.

?

Photosynthesis tokes corbon dioxide out of the oir ond provides the

input for corbon into food choins.

ccbon dioxide

* wcrter

light

-

glucose

chlorophyll

*

oxygen

Respirotion, by onimols, plonts ond microbes, releoses corbon dioxide bock into the otmosphere.

glucose

*

orygen --------> corbon dioxide

*

woter

*

energy

The world's oceons, lokes ond rivers contoin more corbon dioxide (dissolved in woter os hydrogencorbonote) thon the 0.03% of the corbon dioxide in the oir. So, on o globolscole, most photosynthesis tokes ploce in the oceons.

Carbon in carbon dioxide in atmosphere

Carbon in compounds in plants and animals

)

The nitrogen cycle

Plonts ond onimols need nitrogen to moke proteins. The oir contoins neorly 80 % nitrogen. But nitrogen is no use to living things os o gqs. Plonts ond onimols con not use it in this form. It hos to be chonged to nitrotes before it con be used by plonts. Plonts con use the nitrogen in nitrotes to moke protein. Animqls get their nitrogen from plont protein when they eot plonts So how is nitrogen gos chonged into nitrotes ? You con find out by looking ot the diogrom:

in the air

ffi

plant proteins

animal protein

{ animal wastes

denitrifyi ng bacteria in soil

nitrates taken up by roots

fertilisers

\

=r-F\ decay bacteria act on dead remains of plants and animals and animal wastes

nitrogen-fixing bacteria in the soil

nitrogen-fixing bacteria in root nodules

nitrifying bacteria nitrates in the soil

o

the roots colled root nodules. These bocterio chonge nitrogen into nitrotes thot the legume plonts con use.

Decoy bocterio breok down deod remoins ond onimol wostes releosing ommonium compounds into the soil.

o Nitrifying bocterio in the soil con chonge

o Lightning couses nitrogen

ond oxygen to combine ot high temperotures. Nitrogen oxides form. These ore woshed into the soil by roin where they form nitrotes.

ommonio into nitrotes. Ammonio is onother chemicolthot contoins nitrogen. It is present in onimol woste ond deod remoins.

o Nitrogen-fixing bocterio ore found

o

in the soil. These con convert nitrogen from the oir into nitrotes. Plonts ore oble to toke up the nitrotes with their roots.

Some nitrotes ore lost from the soilbefore plonts con toke them up:

Nitrogen-fixing bocterio ore olso found in the roots of legume plonts like peos, beons ond clover. The bocterio moke lumps on

o Denitrifying bocterio

o

Some nitrotes moy be woshed out of the soilby roinwoter. This is colled leoching. live in woter-logged soil They con chonge nitrotes bock to nitrogen gos.

)

Life in the soil

Life below ground is just os diverse os life obove ground. It is essentiol in mointoining the cycling of nutrients thot ore vitolto plont growth.

Soils ore complex mixtures of different-sized rock porticles, humus (deod moteriol), oir, woter ond dissolved minerols. Plonts rely upon soils for root onchoroge ond, in turn, root penetrotion improves both oerotion ond droinoge. Plonts olso rely upon soils for o source of woter ond nutrients Bocterio ore o vitol component of soils, os we hove seen when looking of the nitrogen cycle. Decomposition results in the production of humus. Without the presence of decoy bocterio ond fungi, this decomposition of deod plont moteriolwould not hoppen. Also the nitrogen-fixing bocterio such os Azotobacter in the soil ond Rhizobium in the root nodules of legume plonts such os peos, beons, clover ond gorse, hove on importont role in converting otmospheric nitrogen into o form thot plonts con use to moke proteins for new growth. Eorthworms ore common ond extremely importont members of the soilcommunity. They ore detritivores, feeding upon the portiolly decoyed leoves thot they drog into their burrows. In this woy they help to increose the orgonic content of the soil. Any indigestible moteriol is egested of the surfoce os worm costs, or underground for decomposition by bocterio ond fungi. Not only do eorthworms improve soil fertility, their Beetle larva burrowing olso serves to oerote ond droin the soil. Some species of eorthworm ore oble to burrow severol feet down. This hos the beneficiol effect of mixing up the soil

Soil constituents

Root nodules of a legume plant

Woodlouse

loyers.

Eqrthworms eject colcium corbonote in their costs ond this helps with neutrolising ocid soils. The soil community is just os interoctive ond complex os mony other obove-ground communities. It includes herbivores such os slugs, snoils ond wire worms ; detritivores like eorthworms, millipedes ond springtoils ond cornivores such os centipedes, spiders ond ground beetles. This oll odds up to o dynomic community, but in the context of this chopter, perhops the key orgonisms ore the decomposers: bocterio ond fungi.

Snail

Humus (Dead organic matte0

Soilfood web

)

Biology of work : Intensive food production

Modern forming methods hove become more intensive. Formers try to produce os much food os possible by moking the best use of the qvoiloble lond, plonts ond onimqls.

Foctory forming We hove seen thot by eoting plont foods, for more people con be supported (see poge 308). This is becouse all lhe moteriol ond energy in the plont is used directly by your body. If the some omount of plont food wos fed to onimol like o cow or sheep, then only obout 10 % of the food is converted into onimol meot. The other 90 % is either uneoten, not digested or used up in respirotion. So reoring onimols is not o very efficient woy of producing food. However, mony intensive forming methods hove been oble to moximise the meot production in some onimols. Animols need the right sort of food ond o certoin omount of wormth to grow well. Mony onimols ore reored indoors so thot:

!

rll

'lrt \1,

al\) t "*

l)

il l€

!

:

I

ntensive

tu

.l

\3

J

lri

J, -d

rkey farm

r

n

g

o

The omount ond type of food con be controlled. High protein diets ond odditives moke the onimols grow os fost os possible. o The temperoture of their surroundings con be kept constont. This is importont becouse mommols ond birds need to mointoin o constont body temperoture ond o lot of the energy in their food con end up being lost to the oir os heot.

o

The movement of onimols con be restricted by keeping them in coges or pens. The lock of exercise meons thot they put on weight quicker. o Antibiotics con be used to controlthe spreod of diseose. The demond for protein foods con be met by the efficient conversion of food energy into growth (meot). Increosed efficiency, better breeding ond reduced lobour costs moke it cheoper thon the equivolent free-ronge products. But mony people do not like to see onimols grown in these conditions. They think thot it is more humone for them to be outside. Keeping onimols penned in or in over-crowded conditions con only leod to obesity. Boredom ond frustrotion con result in bizorre behoviour. More ond more people think thot the use of veol crotes ond other types of onimol pens should be bonned. Free-ronge products ore goining in populority os people come to understond the suffering thot con be coused by foctory forming.

316

lv4any

people think that veal crates are

inhumane

E o

D

'Wish I could roam the range

Crop production This field of wheot hos been grown by intensive methods. It is o monoculture, since only one type of plont is being grown.

o

o

o

These crops hove been selectively bred to produce o lot of

groin. Fertilisers hove been used to grow lorger plonts with increosed groin yield over o shorter period of time. Insecticides hove been sproyed on the crop to control insect pests ond herbicides hove been opplied to killthe weeds.

r The former

hos to bolonce the cost of these chemicols ogoinst the increose in the yield of wheot groin. Most of our breod is mode from cereols grown by intensive forming.

,

We hove seen how the yield of some crops con be increosed by growing them inside glosshouses (see poge 196). Inside o glosshouse, conditions like light, corbon dioxide ond

ri ,-:

I

nte n s ive

cereal p rod uction

temperoture, con be corefully controfled

Fish forming Fish like solmon ond trout con be kept in lorge coges.

Here their growing conditions con be corefully controlled by:

o o

o

Providing o high protein diet, usuolly in the form of fish meol, together with o mix of oppropriote vitcrmins ond minerols. Anti-louse chemicols ore odded to controlthe spreod of diseose in overcrowded conditions. Excluding predotors ond competitors.

o

c o

In the UK. fish-formed trout reoch o morketoble size of beh.r,,een 180 ond 280 g in obout 11 months depending upon temperoture.

The benefits of fish forming include;

o Hoving o controlled supply of specific fish of the required size. o Achieving on optimum growth rote ond heolth of fish. o Controlling genetic selection for useful quolities e.g. diseose resistonce.

o The efficient

conversion of food into fish, becouse fish ore cold-blooded ond energy is not wosted in mointoining o constont body temperoture.

There ore worries thot fish forming con couse pollution. The concentrotion of fish in one ploce meons thot wostes ond uneoten food con couse eutrophicotion problems (see poge 336).

377

)

b) How mony cornivores ore there in the food

Questions

web

L. Copy ond complete: Producers ore oble to moke their own . . . . . Producers ore fed upon by herbivores or . . . . consumers. These in turn provide food for . . . . consumers. Deod ond .... moteriol provides food for .... ond detritivores. Feeding

?

c) Drow o food choin with five links in it. d) If ollthe spiders were killed by diseose whot would hoppen to the numbers of ii) plonts ? i) moth lorvoe

:

3. Look ot this food web:

relotionships con be shown in food . . . . ond in food .... . Feeding relotionships con olso be shown in pyromids of .... , biomoss ond ....

owls

.

2. Look ot the woodlond food web: shrews

toads owl