A2 Biology Answer Book

Stretch and challenge quesrions are indicared throughour the Studencs Book with the following icon @.These questions are aimcd to r,.-.,.h and challenge all srudents by using diilcrent assessment suaregies including: a varicty rvriring opportuniries and diffcrcnt question "r;r;;,;;;;;;;:;;:;;;;;:_1.rr.o nro", ,o enabre studenrs to deverop and use a 'varicry ofskills.All srudcnts shourd bc abre to give anslvers ro frcse quesrions and a basic ansrver 'is oudined belor.v for each of them, However it is expected rhat candidates working at higher grades wi'givc a grcarcr dcpr'ofanswcr bri'ging in cxrcndcti knowleclge and undersranding from a variety of sourccs, pages 1G-11

I

Marks arvarded for: Most imporrrnt rc:ic,ion because armost r,' lire on earrh dcpenc: on it' only Iarge scare rvay in which new organic morecu-les arc synrhesised in living organisms and the oniy rvay in rvhich a ncw supply of ATp can bc builr up. any oL.. vaiid point. Marks not awarded ror: without respiradon, celrs dic so phorosynthesis can,t take place. wirhout slnthesis of proteins, tl-rcrc is no AT'pase, so no ATp cycle. Almost impossible to rank reacdons in terms of importancc. Any orher valid point.

2 a

Releases energy rvhen

AT? broken down to ADp in a form available to alr ce, enzymes. ADP and inorganic phosphatc can be rcrorrned inro A r-p by AT1)ase usirg energy iiom universal

b pages

l'l a _-...

reacdons, suclL as rcdox reactions, rri'Jrin rhc cer1. A^ny orher valid poinrs. Evidcnce to incrudc: prescncc in'a, ccr-l rlpcs invcsrigatcd, prcscncc in every species invesrigated, impacr on ceus if ,{fp synthcsis o. br.r-k,ro*r-, in}ribited. Any other valid point. 1

2-1 3

a' rhc cclrs carry out phorosynt'esis any parrs or.rhc prant which are not direcdy exposed to light wil) nor conrain chlorophyll. Bccause not

'b..lFolded membranes givc Iarge surface area. Enzymes on mcmbrancS rnd in sUoma Lo crrr), out rcactions. Pr6sence of severar photosynrhetic pigments to absorb difrcrcnt waverengths of light, Any other valid point.

2 Noneofthepigmcnrsabsorbwcti'thcgrccn/yclrorvrrcirsofthcspcc*um,AsrJrisright is not absorbed, it is reflectcd rvhich is,,vhy plants appcar green_

pages 14-17

I

Cyclic photophosphorylation

Non-cyclic photophosphorylation involves PSI and p5ll

electrons ccfie froffi and retuin to chlorophyLl in p5l no reduced N,.,D produced as electrons return to chtorophyll

etectrons lost on excitation from the chlorophylt molecutes in ' PSli are replaced by electrons from the cx riation of *.t..NADP recuced to reduced NAD during the process

ATB reduced NAD and orygen formed

Edexccl A2 B'olo8y Implcmcnradon and Asscssmcnt Guide rorTeichcrs and'r'echnicirns gpcarson Educarion Limircd 2oo9

rcicrcncc [o non-functioning of s}'napscs / cq; conuol of {moror functions / motor ncurone lunction}; reicrcncc to {cercbcllunr f nlotor cortcx / parictal lobc}; rcference to substantia nigra / basai ganglion / mid

(2)

brain);

convcrted ro dopamine/ dopamine cannot cnter rhc brain / L-dopa can be L-dopa is {casicr / cheapcr} to make / conversel

(1)

PET;

1 tNtRI / FMRI) scan / {C'f / CAT} scan / thermal imaging /X-ravs / and P}iT'] 2 rcfcrcncc to 3-D imagc; [only apphcs to Ml{I' I;MI{i' CAT scan 3 {shrpe / sizc / colour} Jiflcrcncc; 4 densitY of ussuc; of damaged 5 comparison to image of a normal brain / mcthod of identification arcasl

6

refcrencc to moniloring ovcr time;

(3) lTotat 6 Qarks]

Limitcd 2009 for Tcachers and Technicirns oPearson Educrrion Edcrccl A2 Biology Irnplcmentaoon and Assessment Guide

process that depends on or is alfectcd by a number of factors' the value' process rvill bc }imitccl by tlrc factor that is ncarcst to its minimum of light availablc alfccrs dlc amount of chiorophyll drat can be excitcd and

3 ln a biochcmical Thc amounr

drereforcthcamountofrcducedNADandADPproducedinthelight-dependentstage.

If*rcrersaiorvlcvcloflighttlrcninsufficicntrcduccc]NAl)andATPwillbeproducedto allorv the reacdons of

rJ-rc

light-indcpcnccnt stagc to progrcss at thek maximum

rate , so

light is the lirnitir-rg factor. means that the Low levels of carbon dioxidc available for fixing in rhe Calvin cycle carbon dioxidc is casc) rcacrions.rnnnt prn.."d irI drc miximu.r ratc]Whcn this is thc dioxide that is carbon often rhe limrting factor. In rhe natural sirualion of plants it is mosr the hmiting factor'

All of rhc calvin cyclc rceirior.ls and many of thc light-dcpcndcnt rcacdons of phoLosynthcsis arc controllccl by cnzyncs anrl ate drcrcforc scnsitive to tcmpelature.This for a very high rate mcans rhat. cvcn whcn t1-rc light and clrbon dioxidc lcvcls arc suitablc advantage of of phorosynthesis, if the lcmperaturc is low, thc plant will be unable to take thc condirions.

w_

A? Biology lmplcmentation and Assessmcnt Guidc forTcachers aDdTcchnicians OPcarsoo Edustion Limircd 2009

pages 1B_i 9

'/

fhc habirar

is the ,addres

ttrortr[s shou]d ot

organjsm

-

it dcscribc

Ln u'oodrand:

,op

crc.

squrrrer,

uiff.."n,';,.,*l'olt" p..6.,"b-titt'pv rr fox, primarv

Iink hcru.ccn

pages

;;;ii^'"li

2o-23

Thc proccss by rvh.ic are rcplaced

c'rf

b,

,r,n.

t,],re

Irrimary succe:sjon coloniscd by

:) _

r_1,

f$ilti:::*il:f :ff;#::'-.

A communiry reached ., thc, ,t en'l of r serics consisr of of sr " ".u ";" "..-""":-ly

communiries.

{.) tS+Cl

" t'l:i'

1;;;::l ,

shown,

rnjrnals arr.

",n..l:Tuniljcs *r...T.-#J"ffi "#:f;.;;n1;,."jff

Ld

may ir' For cxrmplc, rood njchcs rree_dweJjlng herbivore

_"riuq,/rcr raDDltr , ..;;;;;.;;r;::t:,n hrEe

Full dera:ls shoLrld bc givcn of u,h;.,L^.._ , . of.whichcvcr biomes choscn. ,,lro;;;^":" A crcar undersr,.r;*^ s and ric ortire shc'rrld bc '""0';;;, ur ulc llsbltal^'''"1'understanding

-2'

r"2

tt'hcrc it livcs' suirable examples

'o'."'n "'-top;"l of "tt''o"t^ol Thc nichc Ejoeicirii*;[;i;aiH qhn,rr.r

i-^r..:

.,,,. o,,.j,lni).|ff::::"tr;:,]:'|."'forlowing other points mav be varid Ill":,, olism of the cell nelv viruses.The host ceil" ..a,,^!_^,1 , and causing it rn *-r.^ ;"" il:;":ffi J;:;:'fi ;i IT: ::: .ffJ5i: ji I lil.T'i:::' I1-' F ; T: *: :: : ,Tm ;r,,,: 3li;, il;lil ; ;: m ;*".r*;l

*'

;: fi ::::,

I

Bactcria: Cause diseasc rhrn,,-h ,u^ nndc,rox,ns I hev

"..

=;ff ,,ooo","r*il::f: and reproduce. #::l;l::u.,,, laycrrheyof grou, Gram-n.guriu.

ofien cause fevcr,

il::::'fili:i:,,"Jj:ff

-

ut"..n..ll,,l

.;:"t :::*

,::;::,iili:'i:llr::: "T::';;;;;,;;:;;.l'lTfi * *' o''"'*'

c - i:.,- ;;;.:";H,:ff o,

or

u.",.riu.

.:.,

carbon compounds in decomposers, carbon

*;::::iT;::?:,.,

;I

water.

stages: dead orgaoic matter

.o;uuotuttt rpounds in

decomposers

+

CO2 in air

pages 92_95

$ ts*c]

The ans,,vcrs

varid. Sujrabic

.rbr" ,,:::r11

incrudc sornc or uil

' vecrors:,."rn.*j, ii"li*,:.";;;l . fomires: narural skin ffora and sebum . direct contact:

. .

c

':; ::t''"

ftrrrorving' otr:cr points mav bc

skin

inhaladon:

-"",; ;;:;;.:,Til",#,,tt"

ingesdon: saliva, mucus, stomach acid inoculadon: clotring

'$ Lrrorr*.s

.,.

are enzymes rhlr ,_.r^",-^_. r clesrroy bactcrial mucus rhat line' rvalls L)'sozvmcs ott ..'111t-tan are prescnt in the acr to desLroy bn.,".ir, *;";,';;"t' ur:nary and reproduclivc 'n" patricularly tracts'They are also present,r.r,.r.,"o,"1" Gram-positive bacteria.They and dcstov ural .:.'gt'tlt cnler and might infect <

.:-\ lj) .Phvrl.rl barriers: Skin is a tough

]:i'j:o" """-' tilil: il;';;,

watet

parhogcns

.

ceris and

,."", ,.,",llollcuter

o,*".";,;::,:1::

resp ira ror

v,,,., . Chem.ical barriers:

.

.

layer impregnared wirh kerarin rhat prevents brood-rich rjssrrcs rvrrcre ,r,{,

"",u;;:;*',:*;::?j:j::""t,

Mucus forms a sLiclc

,, o.n,

the eyes.

""

o

*n'ch

lTiJ"'''';

"oura

i,,u,a.

acrs as a physic

; ;",."n'# il'J J:lTl

:

:

"ff :;TfJ

ilr ogen s

Sebum is a laycr oioi top of the skin that con: grorvth of pathor.ni.'ot _o_. _, 1,,. t..i, b", skin b a cteri a.

;;; il; "",1,;:' ::il Tj.ilT..:,,ffi ,X:;

Acid in rhe stomach h desrroyed Edexcel

',

*", ,.";T.1T

pH and acts as a barrier ro mosr pathogens rvhich are

42 Biology Implementation and Assessmenl Cuidc forTLachers

and Technjcians ,Opcarson

Educatjon Limired 2009

iii::::'til

''i::'._..J.:: i -itt:i: i:

l1:iiiiiiii'in: S.1t3.*;r!rr:':'

Biological barriers: . Skin and gut flora

-

and lining thcse arc tire hcalrhy bactcria grorving on the surface

thetubesolrl-rebody.'I.hcyoutcompetcpathogcnsandprcventthemgainingcntlyto rhe body.

Lysozymcsarecnzymcsfoundinn'rucusatrdrearsthatbreakdownbacrerialcellwalls and kill ihcm bcforc thcy can infect the tissues'

Thevomitingreflexejectsbactcriaandvirusesfromthebodybeforeaninfectioncan sPread far.

AnY other valid Points' oaPes

96-99 rclease chemicals known Masr ceus and damagcd whltc biood ceils

o

as hisramines

:'rvlriclrcuusct]lcblorlJr'csselsitttiteutelt,llrrtieulrril,())eilltcriulcs,ttlclilutccrusirrg s4'\ wlocalheatandledncss.Hcatreducestheefficicncyofreproductionofpathogens.

capiilaries lcak-v so fluid, incluciing plasma, white Histamines aiso makc *rc rvalls of rhc rhc capillarics causing swelling (oedema) biootl cels and anribodies ars forced our of

.

and often Pain.

..$Thiteb}oodce.Ilscngulfpa*rogcnsbyphagocyrosis,anlibodicsinactivatepathogens, pain makes you takc care of iniured sirc'

2l]ccauscthcysimplyrcacttonol]-Sclf-tilcrcsporrscisnotspccifictoaparticular pat)rogcn.

3 a

by lowering the A raiscd lcmpcraturc can hclp rhc body combat infection systcm works bcttcr at highcr imtrunc thc Also pathogcus' rhc of ratc '-^""1"'1ion rLPr uuuLuvrr infection' and so rvili be more succcssful at combaring thc

temperalures

blfbodytemperarurerisesabove4O.C,thedcnarurationoisomeenzymesmayoccul causlngp.,*un".,,tissuedamage.Ifrlreremperatureisnotloweredfairlyquickly death maY result'

Tcichcrs an'l Tcchnicians OPc'rson Educa!on Limtr'd 2o09 Edcrcel A? Biology lmplemcnl,lion md Ass6smenr Guidc tor

pages 100*.103

Q rrr" imrnunc sysrem re *: o"o, n*. ."ir;:: T:: ;.T#"#il:: or p arhosens. rhe ceus i' surraccas selfand :l thcm. -'! urrlrrurrs system recognises anack so does

@

B cells:These have rece invading t;;;.;r:ilttor

T cells:These come in t

r\

proteins which recognise the anrigens on rhe surface r.rf .halrilriuc9 a'ribodies to u ,p".in"

- '-eY Sive rise to cloncs of cclrs

pathogen. production of

not

types

'f

helper celis produce chcmicals that stimuiare the chen *:tdcstrov parhogens.

anribodie s. T killcr cells produce

(+) Non-sp.crnc

responses rccognise ,n. ;".J;." ;";:''^t' gcncral reacdons ttttont' non-sclfand iniriate against anything thar is non-se'. o.ll"n response invoiving rhe masr ceils and ,h. The specific responscs o rccognisc nor just Ve ry specific non-scll but andgens

hir,r;;;;:1:;j:: :l.?;,::1,-_".,

p

a,h

o gc

Edexcel

n

,A-2

s,,'. o ;".

*fi

;;,;""lt:-1--'""^system ;,: i " "': fi : il;T #

also

TJJ

t* *Tji1*.11:.,,..

Biology Implemenration and Assessmenr Guidc for Tlrchers rnd Tec)nicians 6person pducarion

Umited 2oos

fages 104-105

C ' *:-

Disinfectants kiil bacteria lrom the area, lrom insrruments etc.This ieducei the Iikelihood of bacteria bcing uansfcrrccl from cnvironrnenr to the patient/wound.

'

Antiseptics are applied to skin and to wounds.They kill bacteria and so reduce rhe likelihood of wounds becoming infecte d, bacteria getting inro blood etc.

'

Anribiotics desroy bactcria rvithin a parienl and so rcducc rhe likelihood olinfecrion passing from one person to anodrer through cither dircct or indirect contacr.

@ a o-

lndrcl80Os'3{J0rvot.ttcnrlicclperl0OOOObabicsborn(600-900womeninfectcdpcr 100 000 babics born). lh thc carly 20OOs cicar-hs terc 0.85 \romen pcr l0O 000 babies DOrn

fft"i. G \-/

work was important bccause it shorvcd clcar cvidence for rhe eflectivencss of antibiotic drugs in trcating a bacterial infection which killed many young women each year.

It

feU short of modcrn erhics and standards because rhcrc rvere no lab trials on dssues and cells, no conuol patients rvho did not receivc the drug or who received a placebo, no doublc-blind trinl, probably no plticnt pcrmission for rhc trcatmcnt sought, and no

ethics committee decision on rvhether thc uial should go ahead. Other points may be

valid. pages 106-107

(! fi." following describcs the basic inlormarion. Orher dcrails may be found from research. \r ' Ronald Hare, one of Fleming's young assistants, found that penicillin mould grows best at quite iow temperatures.

' Dr Cecil Paine,

ano*rcr onc of Alcxander Fleming's pupils, was rhe fust person to try peniciilin our on peoplc. A local nriner got a stone in his eye and had a massive infection rvhich was making him blind. Painc washcd rhc eye with his penicillin cxullct, and thc cyc rccovcrcd. Painc also usccl his pcnicrllin wash to trcxt a tiny baby which had pickcd up an c1'c infecdon as it was born.The baby was curcd and irs sight was saved' Painc nevcr publishcd what hc had donc, bur he taLked to Howard Florey, a new professor at the uruversiry, who wcnt on to follow up the work.

'

.

Norman Hcatlcy rvas a kcy man in drc Oxford team. Hc worked out a way of making enough pcnicillin to text it and carricd oul thc following cxpcrimcnr. Eight mice rvere infected with bacteria which would kill them in 24 hours. Four were given penicillin. The four treated mice stayed hcalthy - but rhe orhcr four died. In 1940-41 Heatley dcvclopcd special pot vcsscis so hc coulcl grow morc mould and so collect more pcnicillin. In just a fcrv wccks hc had madc cnough pcnicillin for Florcy to uy ir out on a

'

lully grorvn man.

Mary I-lunt brought a mouldy mclon into t}rc jab tirat shc had found on a market stall. The mould was a new sort of PerLtcillilnz which produced much more penicillin than *re originai srain.Thc ncrv mould rvould also grow in big fermentation tanks ivhich was the break*rrough which cnablcd industrial producdon to go ahead. Ms Hunt got rhc nickname'Mouldy Mary'.

lldcxccl A-2 B . 'rsy lmplemenlalion

ud

Asscssmcnt Gu:

I

iorTcacl)crs andTcchnicians opcarson r :rucrtion Limited 2009

l^

t2/ u Ant rrvo examples of rhe aclion of bacter ia clearly explaincd. b Bacteriocidal means it kills bacteria.

Bactcriosradc means ir stops bacteria grorving/

reproducing,

" ,arH::lTi::i_ infecdons,

pages 108_1

1

some andbiorics are bacteriosraric.ar.rerari'e)y rlrc

;x:::;Tffj::::1J,": " G.;

low concenradons,

inlccrion,;;;,";; ;;;","""."

1 1

Mutation causes a change that arfects the way the antibiotic gers into or affects The antibiotic is a selecdon the bacreria. facror by rhere is rapici evolution so that rhe

t "

f,l:,

Liirirg.u u*.lia thar arc sensidvc ro it.Thererore rcsist*, orn. i..""r"s lre mosr

.orr*o,,

iorrr,.

The answer should include some or ali of tire following. Orher points mav be

Keep antibiotic prescripdon to of treatmcnt with anubiotics;

a

minimuml ensur fJlat padcnts complete the course carefulwith the use of broad-specrum

be espccially

b

anribiorics in *re case of C. dilficite. Minimise exposure to reduce rhe lik€lihood

of rcs. mutation being selected for. Make sure that rhe whorc course or.anribio,,., ,, .r,rur, srighrly increased resistance rvith onry a are definiteiy

3 a . b

".:::;l;;racrcria

"u.o Broad-specuum andbiolics wipe out large numbers of the normal gut flora dfficib can get established, produce so c. ,"*ii; ;;;:;

Narrow-specrum andbiotics are urscred *".:^:::::,:Ttt"*'' rvhich are causing spccific infcction. so they arc lcss lik"cly ; ", ,;;;;:l-tms minimise opporruniries for r,,tora ancr so

c. dfficite;"

4

a

il";.::,ff,lt.:::

}ixamplcs of good practicc inclrrcic: . Docrors, nurses and. other health carc prolcssionalr

,..""J;;t[* jTiil:';'.",':"t

arcc':hoi based gers between seeing parients reciuccs chances of passing ti.,..n *. So";*-;;;;

arcohor gers

.

,o

,h.rJ;.

orrimited u,.

Avoid clothing

i. o",i,"iil,*Tff;:h,"1"J,": ,r

which might carry bacrer.ia rvarches and rong_srceved shirLs ir-he.,* HeaJrh professionals ,ear w steriliscd scrubs

lrom the

outside.

from pat

""

.

.;;'";:;r.;;:::,ll:.',,e,g.

rong rjes, wrisc

ail drc time to avoid bringin$in pathogens

'

Monitoring parienrs lor inlecrin^ r_t-rvhen -r_:-_. admitdng and rreaung and nursing in isoladon avoids spread

'

Encourage visitors ro u inlection into hospital

' .

"ro.*.;j:l:t'ion

'fhorough

i:':ffiT il:

use alcohol gels to minimise risk of

bringing

cicaning oi hospirai.war