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
.
J
l'c
tre scme urrir condirions change again.
planrandr",",r,.f....r.;.r:rilil::il::H:"::,;;," a",1-ul
I
brre rock or sanJ dune ""''t'secotrdarl'succcssion
rings bur
rnor.i.,,.J.*
The answcrs shoulcl jncjudc sreadv growrh
somc or all of
num-ber ;;';;:j^:::t't' of spccics
soil devetoped.
on land tirar
rvas
rolJowing' odrer points may be varid.
condidons changcd '" Tr"i :tj: "" a period and nrore "tr'r*"*i*'i"as t nt4-e0 as r,fl drc isrrnd had *i'n"",;;;;;,ii 10""' rrrey broughr ;l:::.:'oon lheir b",ii;r';;;;,"' tcrultrv' Oncc bircls colonissd j51sn.s droppings n"O".* rerriJicv of rle ,o .j_tlltt soil with r
d*'siepg6 ,r r..
b
some
rp..r.,,rt.h,il^'lo" "to'';;';;;ril*"'ed isl:rnd
again reladvely rapidly'
rheir
,,rr, ,o;tttut"o r brceding poprrrri^i:t:.tlc but crnnot survivc 'nd to establish island., oin r.l,l,oiplanrs So .;;';;.::"*t:" or l.isnrs lta'c
r-hc
cumuJaLive
courd drop
c
If
rimcs than
rJrc prcdrcrrc_rrrs
drop
bccn obscrvcd
on "t" ";;r;i;;;: ro..,"r," n' .",.,0.,i1,1.t '""',,.;;;;;'J;::::il:i,ilj;::.#i:r'.*j',",,, by
s
.
row,, , o, *,Tl'li;:;l:Jil:i;:,1,1"-,::::l mOrenCwspcCiCSbecc_ ---'! rut.u wlll rcma :: ::J :me as
cstabrishccr
pases
24-22
1a -lhe non_livjng
.
I
1 y
-
elemenrs
s; , ii, s couJcr evenruarJy
o"r;;;v:i,ffi::';J::::or1'rcn
so up
of environnrcnr iu which . i;;- .;':::i.T: :o :il?J,* on rncludc organi or,.lo,.l;.,,::l;T:::j.ililj:::Ti; ;::;::: :,::l ln,.n " ",-,Lr lsrcvant
living. Dxrmprc, ll"^';otrr'. pH nu of :l.. the roir. soil
.
^, nolottc factors dctcrmir ctc.rhis in rurn crc.Thjs decides
ir
r
unv
ap pop u,
a d
or
pOtntS sUcl
orrbe ot rhe soil, soir, rhc rhc lcnli
*
rvatcr avaitalririry which ptants *i,,:.'j,,,,,,, pranrs rvill *',, be '";;";..r;::,1,;]l','1""'t o.li,'"',].i:l]"'"1"i" able to erorv *. *.t".,. j:i;';Jii::.::J"i:::'""1:':l'11., *ur"'r #Xi.'ltJril,, ".d :i1:.5;;'#.T#l:1il:H;l'ff "*.. col :oronisers oni ers of abre ro surv,ve. n re a, r r,;;; rn rerms ortr. ;;.;":r' rX'.. i.:irl "r,",.;';;;,,:J|j:::,'",T:.::.bc r.,i] in,rurn affecrs s
a
a
An1' 5ri1r61. cxamplcj sucir as in a wind1, en'ironmcnt watcr will evaporate from the ground morc rapidll, 5e rvill bc lcss availabic ibr living organisms, high light lcvcls but low oiygen levcls meitn many orgarrisms cannot grow rvcll and rcproduce etc.
Any suitablc examples dcmonsuadng an understanding of how the animal/plant adapted to the panicular abioric factor sclecrcd.
is
pages 28-29
I Is+c] 'lhe answcrs
should includc somc or all olr]rc following. other points may be
valid.
Any rhrce suitable cxamplcs, including one bird anri onc mammal, with clear explanation ofhorv tcrritorics arc markcd and defcndcd, e.g. scinr marking, physical displav/dance, fighring.
y \vith liule
biodiversity, if onc organism is alfccted by discasc it will have a major in"rpac. on the small numbcr of otl.rer organisms in the ccosystcm rhcy won,t gct eaten or tleir prey numbers will fall subsranrjaliy.\Xuirl lrttlc biodiveLsiLy rJrere will bc fcw other available food resourccs. Also discasc is ntore likr:ly to sprcad benvccn inciividuals where there are fcrv bulfer spccies. In a more di'crsc communiry, changcs ciue to disease are lilely ro havc lcss of an cilccr as rhcrc is much more varicry of food choice and more buffcring organisms to prcvcnt sprcad o[ discasc.
pages 30-33
1
inrraspccific
- bctwccn mcmbcrs of the samc spc:ics, c.g. for territory, mares, food. I^raspccilrc compcritior tc'cls to affcct drc rb'.
-
lorv rcsources, rnuch compcutron, less reproduction and more mortaliry
-
r dccrease. Plenty of resourccs - littlc coinpctirion, Iors of breeding, Iorv mortality,
numbers increase. interspccific Interspecific
- bctwccn mcrnbcrs ol diflcrcnt spccics, c.g. for space, food. - this lcnds to affcct the diitriburion of spccics in a habitat and also the abundancc of spccics - thc biodivcrsity. If onc spccics comperes very successfully against othcrs,
it wi'll tcnd to drive thcm to extinction in thc
2 [s+c] Thc ansrvcrs shourd rncludc
arca.
somc or an of thc foilowing. orher poinrs may be
vrlid.
a
Adding food - hare dcnsiry more dran rriplcd. Excluding predarors - hare dcnsity more rhan doublcd. Ferrilising d.ie grass had no major effcct. Adding food anri rcmoving prcdarors - harc
clcr.rsir,v
wcnl up by a facror of abour i5.
b Ifaddfood,haresbrce,rmorcsucccs:fulry,burmoreuiil
arsohetakcnbypredarors
which will also breed succcssfully. So rhc impacr olrhc lood on rhe hare popularion is not luliy illustratcd in thc population numbers.
Edc\ccl 42 llioloS] Implemcntatioo
an
Asscssmenr
cuide fol'ltachcrs and'ltclnicians ol'carson t.iucrtion Liriited 2009
-**'se4eu****;"''**
popurarion #J ,.'*,1 l::l:::":.0." a resurt or *.'-,1,i'i'"1;#,;ffiTiffnipuiadon,
hare other racrors 0.r,"
Jlt;:*
L
o',..,"#*,ii', l"*.- iTl,. ;*:::,:4
ffi
lTj T;:;;
",,n::
j: :,il:ff fi ,l.,ilili *
:
* : *o,
i"
u
*, .,
,"JJ,i:;:i*lfii:TFl.ili?lllT;;T,".J*ji::,;:,::.fi :::::ff ;;il"';i :a;, il j:::'"il,3;::
:::;: i'Jili;:;"T i: : ;::: :mltri;IT ii I)ensiry_indcpen
.,"-R..,
r,,.
ff
:
I ri t,tr
H Ixi
"".
f
denr
r;H
il; ;;..Jil:::::i,f
1",'hl,
rlc
::l
a;;.'
"1
?.
jl jrirfi i ll ;::T* :* i ".,"-
disrribu r io,: of r n^^;^
oecorncs densiry-depcnd.;
Pages
I a
.
;;;
34-37
Algac and coral rcr
".;;; c .r rioush ;, r,,,
b
' . .b
; : J :.i,il.:lTff ,,l..:.ilffi ] cn d il:: l::T- :"*r::::vrvc:, rn: oa rvii parLictrlar s
b opcn
2 a
;
*.,
;;;:,11100r",-,up'od u'rion 11..' procjucdviry
n.
, r,;s.,i.;;, "." ,;:::
proc,ucerJ,"
on total
,;;;:t'ct
proclucd
;;,;" rrcrc is
J;# a
o."ur.ur',, ""
j
t
s
urface
1:,'1,::'-
cnormous amount of opcn ocean so
consuners; '..m*",*iiffi:ffi::,,j:# . .., B.e%
(r 6.7
;';,;rt r",*0,.**"".' anr
isn"'. vu,er
-.-
30 1/3
=
1o'o%
would be roo ,r.r.,in;*":::l rvirhin compric :'
ccosysrcm,*o,jil
Any rcasonable wirrrin biomass
r
; no\v mush lishr, warer erc. is
.Densiry-dcpend.",;;;:-:"
*;
a
"*,,1.1"*,,"r;:,':::::],""
assLrm
using
as a
il:;:f.l
food wcb, can
*'*
stucJics
,".,,r.';.:'j":'-o'*
spccics, qsLirnr,., species which "r,;;i,i.ll]:,:^.Juding transfer in,o ".. ".i" ".i^",i.. "," in nurnber, u ,p..;., ma.ng csrimrres
*".i.
l;
*:rr-,:rr.'n
,^ffi tr *,iriilH?t x, :,r":,i, #*.:?Im ;;;::'
;ili:::
""I
u"o"iru,l11lll*i:iJii::::* or.n;#"r'n*
of
38-39
Pages
points may be The ansrvers should include some or all of the follorving. orher
1 [s+c] valid.
than normal The link shouid bc made bctwecn releasing carbon from sinks more rapidly and morc rapidly
$an photosynthcsis ctc'
can removc
it'
othcr road increasing intjusUiaiisarion, clccUicity gencralion, cars and of carbon acroplanes, ali producrng carbon dioxide cmissions affect amount
i'Z\ Ar-osohcre:
'J ,.hi.l*,
dioxide in the armosPhere. dcath rate of organisms, Soil organic mattcr: tcmpcrature (rate ol acriviry o[ brcrkdorvn) any scnsiblc altcrnativc. Occan: tcmperature) any sensiblc alternative'
Nlarinescdimcrlts:c!osion)acidiryofrvater,acidrainctc.)anyscnsiblea.ltcrnadve. Terresuiaiplants:seasonofthcycarintcmpcratcareashasabigefiectong}oba.l photosynthcsis lcvcls, dcforcstation' crop growrh and harvcsting' Pages 40-41
p.opt" could stop eating becf and using tlairy producls, bccausc millions of people around as a major part of rheir dict and big ,r.," *orro reiy on mcat and miLk fiom ruminanrs
i'il V
farmingintercs$havealotofeconomicc}outand*'ouldobjcct.Anyothervaiidpoint.
2[S+C]-l.ircanslvctsshouit]irrcludcson]eolallofl}rcfollolving'othcrporntsmaybe valid.
Thegreenhouseeffecrisvitaltomaintaintl]cSuIl.i]CeofthcEarthatatcmperatule levels of suitable for life. It is thc enhanccd grcenhousc cffccr, clue ro increasing greenhouse gases, that is potentially a problcm' pages
t @
42-45
20.81%; allow i9-21%
sanic or sinrilar Carried out ovcr iong period of timc, r,ery large numbcr of rcadings,
measuringequipmcnlusedlhroughout,areaoflolvairpollurionetc.ADyotherrelevant Point'
y':', clives a much longcr timc pcrspccrivc (rcadings going back over a thousand years), V last coupie .ho*,. narural falls and riscs in carbon dioxide concentrarion and events of ofhundrcdycars.Anyclt-lrcrvaiidpoints.i{clirrbiliLy0.2ppnr.Corrciadonwilhother cvidencc.
€) ffr.
data shorv rhar armosphcric carbon tlioxidc icvcls
hlvc increEed.They do noi show
the sourcc of the carbon dioxidc'
A
\) a
.i^--.^,:.r.,..^t Jtuocnl s}rou}d questior-i validiry of
c1ata,
Staustical ncdrods used, inciusion of uce-
ring data in original'
b 200svcrsioncontainsalargcrnloulrtofcxtlrdttalronrhundrcdsofstudics,nvo
uee ring diflerent starisrical methods used, figures calculated both wiih and rvithout data. AnY othcr valid Point'
Limitcd 2009 EdcxcelA2 lliology lmplcmenreuon rnd Asscssrncnt Cuirlc frrr'l'clchcrs rntll-cchniuirns C'Pcrrrorr i}lucrtion
tt.t
pages 46_47
1
Graph A shows glaciatior
;,'.'.'T.f
tr;:*:J?:ffi ff :ffi,ill,,;i;lTililTJf ffill[ jff :
Graph B shows close correle
1lt Parlern beLwcen lcvcls.which e'ets. which comcs lemperature and carbon ,.-ogruture .on-.., firsr * langc inj::t"'.'*llru...: nrra--.il"ri dioxide dioxi carbon dioxic.lc or change --."^ -":"t" lrr in rcnperature? tc^perature? 86'7%,70.7%36.70/^ tn zot carbon dioxide from frn* r^.-ir r.. , , lossil fuels has incrr :ased rl'1u1c ' --u!q mote than uran otner other sources. a a E'idence sources. E'idenco ofcarerur ^F ^^-^.. research rn.r .L:r:---. up tcrms of terms rlrc rrrcnsrrrs orclrriry clarity of and *cakncsscs in oridcas,::HlJ:i:l:::.::^'tn idcas, rcliability of tlara ctc.
.r#::
l^:"0
a.
closeness of dara, rvhich comes
*: c",*;;;, ffi ::::" points. valid pages
I
,,"10..^,ure or ;ffi:::ll T*: validity :: ::^?.1tf Iiability of and
possib,e
Any other
4&51
t;;;;i
r
i
ve ro
reduc
e
".,
o
enhanced
ffi ;' ; ":'#::-i::;*:"TJililii
levels thought to cau
,...*o,1lo*t* ur" .T.,, ,"..".ri;;;;;;.use
on mounrains, ,.r, poies.
;;
"; ijj;;",';
2 a 43y0,2.7yo b t5Omm c Increasing carbon
"'
dam,
Any va)id poinrs sucF as; rmpossible to predicr ne don'r know ci
i3)
re
".
.rise in global temperatures due ro
causing
melring of snow cover c" ?iffiututt' nperatures and mehing
This .rur", .l"1o.I -lse ln ltrrl"g average
sea"levels.
of snow at
Parricul:rrlV affccts disr
::TR:,T,1; arc s wh r e* a
e
j*i
o c,im a rc c,ranse
;."
##{r i:;:: l:::.:*J:i:d,J, #il ; :li*;;
;;
-
ri sins carbon
:il:,""#
; :T:,H i : i[,:., ", Look for claricyof thought and understanding --.'"lrurrrg of or ure rh, possible sequcnces ofevcnrs, pages
4
l"
52-53
I
Any valid poinrs here. h
:]: T:;T ;l"tl I_,*, I a, n. .n1b.dy can ln*:T";* jt fli;;tot]'utn* counries cannot strive if " *" 1""*tJl'on'nt though
lhar invorves n","i^d, to be unpopura. n"r,lll ", " rnevitably unpopuJar
in"'""""
,::.1t,::o *0"'
2 IS+cr The answers ",,n,n" valid.
--
morc dcvclopcd counrics *'cn emissions' politicians don't
'" ';;;:;;.i '"0 t";,;;:;xrde
rvant
"" '"0'"li"'i.i:i.:':J::"::'-",'":icirv/peror
etc are
- -"ourd includc some or ail of the fo.llowing. other points may be
Answer should cover rhc
ansrver, and
",,;.;;;#J;1,1,]tii;illJr',ll;.1i:*,,thar
Edercel A2 Biology Implementation
#e
rnc
,nereis no comprete
forTcachcrs and rechniqiaos opearson Educadon Limired 2009
Arges
54-55
( 1) I'rorcomicsistJrcstu.ll oIali rhcdiffcrcntJrrorcinsrharcanbcmadeasaresultof
*ie
genomc throughout thc lifc olan individual, at all tie diflcrcnt stages of developmcnt as a rcsult of differenriai gene expression. Should note that there are far more proteins than
,
gcnes. Genomics is the srudy of thc
DNA, thc
se
qucnce of drc gcnes and the specific
alleies in place in an individual.
y (.1) Diif.t.n, allelcs arisc as a rcsult oi'mutaiion - changcs in rhc scquence of DNA bases. '' Chunges in allcle frcqucncy in a populadon usually occur in rcsponse to enviror,,mental changcs.
lf
a particuiar allclc or combination ol'rllclcs produccs a survival or rcproductivc tle organisms rvhich havc thcm so thcir oflspring are more likely to survive
advantage for
and brced again, the frequcncy of rhe allcle will increase (e.g. Malpeque oysters from AS if a particular ailele becomes disadvantageous, the frequency wiil
levei). Alternarively,
dccrease (c.g. Biston bcuilaria from AS lcvel).
pages
56-57
$/ In ordcr to plant the apple orchards
huge areasrof natural bushes would have been ploughcd up.-lhis wouid have dcsrroycd many harvLhorns, tre natual habirat of the flies, rvhich in turn would havc lcd to some fcmalcs bcing lcft rvith no alternative but the apple uccs on rvhich to iay drcir cggs.Thcn some of tJrcsc flics would have had aileles which hclpcd thcm rccognisc thc sccnL of thc appics, or digcsr applcs cffecuvely, or lay eggs ar times that fit the pattern of apple uee llor,vering and fruiting ratler than hasthorns.These flies would be most likely'to survivc and pass on rheir alleles, thus changing the allele
lrcquency in rhe popularion and moving towards speciation.
2
Any suitable cxamples.
arges 58-59
* (!)
2
tn ordcr to mcasurc gcncdc divcrsity, to idcnrify relationships berween d.rfferenr species, ro uack the process ofcvolution, ro idenrify lraud in foodsruffs such as caviar, to idendfy ways of conuolling discasc. Any orlicr suirable cxamplcs. Ilecause thcy are prescnt in
a
rvidc rangc of different organisms, and so rhey can be
comparcd.The gcnes mutate a[
a measurable and suitabie rate, which al]ows the time sincc cven rclatively closcly rclatcd organisms shlrcd thc srmc gcncs to be calculated.
pages 60-61
a f}) V
Fossil evidcnce is limircd: only relarivcly small numbcrs of organisms are fossilised, small nutnbcrs oIfossils arc found, fossils c,ltcn nor intrct.Thcre may also be
similaritics in anatomy duc to convcrgcnt cvolution. Any valid other point.
(9 ONa
starls to dcgradc immcdiatcly aftcr dcadr so iimircd application. Mutarion rares of diffcrent genes varies considerably so timing can be very diflerenr depending on
which gene used.
c
Edcxccl
A2
BioloS-)_
Evidence from any one source has limitadons and potcntial inaccuracies which reduce its validity. If evidence from different sources gives similar results, the more valid are any conclusions drawn. Similarly, using diflcrcnt sourccs can show up discrcpancies and prcven! time and money being wasted on erroncous data. Any other valid point.
lftPlcmenlatjon and Asscssment Cuidc for Teachcrs anilTcchniciins G)Pcarson Educrtion Liniled 2009
--.***sa-msmrrtu'Liui.;;o#"***;gggi* i The r ns rvcr,. "s r."hould includc somc or all of drc loilorving. valid. Orher points
@
t
t
na
may be
Helps to validate nerv rr
bv presenting ir to pe
sevcral reams
t?' conslrucdve criticism' ,r"0"..'ullilt-t when in ':'utt' '.t.i*r;J:"" n.,:l,u:: to bc aired of all their findings cooperadvc rcsearch u.;1'ot" ^t;^;;;;i"n'tle'aliditv o ; ;; i,' x ch n g c JJil::"'-;t'; li ii1 iiii' "'ill' o, r* * ]I"l'o'"' " ln ", rs
c
confirmed. Anor",
;
a
l)isadven12gs5.
",,
"
prcssurc to nrrht;.r, .,,..r .. attd rppcar at
,lrive peoprJ ro runding sroups can - ca'y rnor;ring
co'fcr, ;il;"rJ:tlishr}cv have;"*r;;;;';:t"t"'can
.ourrh.l"
,.,n.r, o..,lll:pul"'
skcw rescarch and Vcsrcd interesrs and Jarqe
p'p"... T,ilin-''rdara' ,'a'cr
car)
minimise audicnce qer Bood .r;';;:;; tccas rvhich go u.l.t'l:tt agairrst n **rtr'\cw ""*ti,"-.* ;;#JJ.'.:,:':'J.::: .*,,",,,.""i, * "o1tjl ; ::: ::*il, ff
rhe accepred view can o. moders. peopre need ro be mi ri ga r es
Edexcel A2 BioloEy Inplemenurr'on
n:I;l;l;
and Asscssment Guide for Teachers and
-llchnicians
(,p€a.50n
Education Lim.ired 2009
pages
66-67
1 a 'lhc
hcat of the body is producerl as a resuh oi the mctabolic reactions taking place, parricularly respiradon in active tissucs such as Lhc muscles and rhe brain.After death thesc rcactions slow down antl str rime he a t energy is i o. t uy,o ai"ulp,., :1111;ll ?J,i evaporadon so &e body cools down.
;:"::;:::*:';::l? ::ff
$.
b rhemctabolicreactionsdonotailstopimmcdiatclyaftcrdeath-manycellsconrinue to respirc, conuact' rnd so on, unrir arl rhe availabjc oxygcn and ATp is used up. so heat continues to bc gcncrarcd in the first hours aftcr j.",t-r, at a slo*,er rare, so body tcmpcrarure drcips but rclarively slowly. "trr,ougl-,
c 'lhc
tcmpcralurc glallie rll bclrvccn rhc boely and lhc cnvironmenl wili affect ratc of cooling, for exalnplc if somconc dics insidc a warm housc the body rvill cool down more siowly than ilit is on a cold rvindy hilisidc, so rhe cxternal temperarure and. wea*ter condirions have to be takcn into considerarion. A naked body rvill cool much fastcr by convection than a ciothed body, and a body *,rapped in blankets or a duvet will cool down cvcn morc slorvly due to insulatron..t.u"ttody will cool laster than a dry body as a rcsult of l.rcat lost as drc rvatir cvaporxrcs, and dearh in a warm bath or some lorm oiheating will also change rhe raie of cooling. Even the body leside posirion ar{ects rhc rltc of cooling a srretchccr our body has a much bigger exposed surlacc arca 10 volulne ratjo fiao a curlcd up onc ar.id so wrjl cool dorvn faster. All of thcsc diflcrcnt factors huvc to bc
guidc to tirc tintc rrf dcarlr.
takc'
ir-rto considcr:rLion rvhcn using tcmperarurc as a
2
vcry littlc differcncc
3
Llmitcd valuc bccause, although thcre is a gcncra)iscd parrern ofrigor, there are large 'ariarions rrom one individual to anothcr dcpcndi'g on factors such as:
as rhcy arc poikilothermic and so their body temperature is normally vcry similar to rhe ambrent tcmperarure.
'
amount of ATP storcd i;.1 tic muscles ar rhc rirnc of'dcarl.r which depcnds genctic tendency and lcvcis of fttncss
' . . '
Icvcr oI acrivity bcrorc dcirrh
- rr'rv nruch dr-r) hus bcc' frc point oi deadr
uscd
tempcrarure oi the individual ar
teinpcraturc of rhe surroundings spccd ar rvhich rigor passcs ulso cjcpcnds tcmpcrarurcJ acdvity of cnzymcs.
o'
J vf,ricty of frcrors sucjr as cxr.crnal
Other examples may be valid. pages 68_71
t
srallc is causcd by r'hc coroniscrs - rnacrobic bacLcria. EqTymes rrom lysosomcs cells releastug cell conrcnts on rvhich anacrobic bacteria grow. As more cells are broken dorvn, the bactcria sprcad.
ll:,lt:" orcak down ' . '
The bactcria are rollorvcd by a numbcr of species of flies, c.g. browflies, rvhich lay eggs'The larvac (maggots) leed on the rissucs, bre aking their down further.
As rhe body liqucfics, adulr ilics can lccd on ir too. Bccdcs arrivc whosc iarvac lccd on maggots. Parasitic
Ede\ccl A2 tsiology lrnplementarion
anrl Asscssincnr Guidc for'rcJchers
rvasps lay their eggs in thc larvae.
!ndrcchnici:ns opcarson E(ru*iion Lrrnircd 2o09
*ffi;;;
it drres
il;*
""* ",""o in. When *;"""'move ,n".,", *,,i'li]::"f *. body arc roo
.
h i,
r"
*one =:r1;av, .h.,uin
r,..,r.i.t'
t.l-,e
Ehcete fiies
; Jj ;::XT:l: T::: ll_,,.*: any more, bcede . -.b ldrrass bcedes,
J
morh iarvae
, ;r"^jr::,;:;:::::
s'rqrsn[ spccics such'as
ham beetres and
reed on the hair unril
"'. ,",;o:.; bui t"t ".;f,l:::.:'ll:'"' ''ct"a,. ."icntn,lutside)' "*"t t'iio'turc notj'ihsr'de
tnd
JcvcJ
onlv drv bones arelert.
'r cxpusur"'r 1l, "i
n:ilH:i:; ourd bc r,". ]'-':','"u'o';;;; of rl-re cllect .iil,f T:::*, t'he ratc of on dccn-^-^: ' clrcmt*,l."lt rarc and,"*". For exampre' llll rcrcLicns r
avairabiriry
3
sh
cnr pera ure
"r
;*,.l#::]'vmic rllTililll'l Y to insccc t;t"-^,:,:.
-
tl.re
lcvel
foir,
succession
"'*;'t"j:"n' "tt-ttrr.. ,fri,i;?::ff;tt"t
,long *in'o]..jotvs-a regular patrern sor bv e. ort'irol'rruion th" condiio,,;;;;:?;.':'*ining fie srs.c ors,,"^- ..
ts+cJ 4
a
n"'"'t'.*,.
Exposcd ooo
in a bodv'
c s c cn "ri",",jl'"[,t^""t1]:1:,0"'" ^;r,;,;;.:ff:on
ss
ca
H'ruiii::: :;x
;:;-.r ;:'.'";ffi::l;r:^tdm,*i{[$:":,1""i',#l',n:J;:::"?.t: .h"ng"", ,, ., ,I_tl-oeraturc r; ;;: ;'r[. ".. il;;::;iff::: y or c jll'j:'1,'. -" '-rirpcraturc lssomposing :: ":, ;:TffTffi
il:li:ii:
1,1"
shorvs less r
a c ri
b
vi
th
r
wrth obtaining
''
Disadvanl2ggs. organisms,
c
ff
fcwcr cr'hical issucs'
l::::'.,'';;":;ll arc not pcople,
'"'"
^
orpis
;:].,j,:u"'
Advantages:
nurnan
rr
Lhe r
"'
d
jrccdv
rcrcvanr ro
",:::]:: bodics,,,;li:1^,::::'"lJ*r,-.,iri.:..
ny o rher,.,.
^^--
rewer probrems
so r,hcrc
n
;r;;
;:;,
cre
h
um
3
n
rc m
ein
s
r
;;";:
pages 72*77
I
carcasses,
in the
'ffi iltit:f;:t'-$;',;.:;:li:.:[::'i;']Ji"t""it'_1,ii."",,," a;rr.flgt
Discdvanragcs:
A
"
are duc ro variadons
organisms.
AdvangSgg5,''
::.,:,,,1r,
,::::'tisation
of hurnan bodies
ffi l'ffi :XT.H: :ri:l:,',
rnore informar.
*r* fi 3j x:* *i""L" :T,Hlt,fr l^i" i:;:{''i",".. i:*;J}iil:":x,ffi r..,,., I*"^f 1"'"''" '1's imp'r'[an'l I?J. H' i,:ffii;1":,Y::-: i,:ffi i;t t**i $ffi:::::l;H"n;;:^" ::l it ; H ff ::,;T: .*. :id;l : ::1,r,: Jff;;:.*.; il: ;;::il"I.,].ll ii,i ; :::unna n, rc', c, ":j::il :: cd'' i,"..,..m ;ffi:: ;t; *m#:friifr ilr i;:I T: J':..l.ffi j:; *iJ":,?#;:*ff i'i,rffi Ili,lliHli-..,.,..il::iii ffi.:,":,?il:,,.";;;;il:'";ilil:iil*.:j;:.J*j::i',,T;l;;,: =" ;Ji ::: i:: _TH#:;T TiH[:1 ,o::::'" 't "..i'"-""'il,.j ;:'^:::T'*"" "
n r
is
:
rc
.
n,
am.ino ac.id cha.in.
Edexcel A2 Biology ImpJcmcnradon
*:
s,,w. or,h or rhee three *u ee
ff
,u acld ln a specific place in an
and Assessmcnt
Guidc forTcrcllcrs
andTccl
uicianscPors"n'
-
n
2 [s+cl
-fhe ansrvers should includc some oI all of the following. other points may be valid'
.iianscriprion:ArcgionofDNAunravcls.onlyrhc5'primeDNAsuand(thetemplate uanscription or anlisense suand) is uanicribcd to give a singlc suand oi rnl{NA''l'he
is
broughtaboutbyanenzymecalledDNA-directedRNApolymerase(RNApolymerase). bases) on on the DNA givcs risc to a complcmcntary codon (uiplet of Evcry rr.iplcr "oJ" Apart in RNA' rvith uracil replaced tire mRNA. Every rhyminc in tl-re DNA rempiate is fromthischange,tlrenewlySynlhesisedl{NAsuandhasthesamesequenceasthenontemplate, coding or sensc slrand of the DNA' membrane and Translation: mRNA molccules pass thIough the pores in the nuclear
movetothesurfaceofrheribosomes,transporlingtheinstructionsfromthegenestothe
sirco[proteinsynthesis.Eachtl{NAmoleculehasaunitofdrreebasesaroneendofthe molecuiek,'o'"n",thcanticodon.EachIRNAmolcculcalsobindstoaspecilicamino acid cJcpcnding on thc cotlc of thc anticodon'
.fhcribosonrcsarctlaclculrol.alargcatlr]astlrrllsuburrir.-llreyarc5O%llNA.Thcy surroundthosepartsoithemRNArvhic}-risbeingaclivc}yfanslated,andthenmove
alongrodrcncxrbit..fircirjobistoholdtogcthcrrhcnrllNA,IRNAandcnzymes controlling thc proccss of prorein synthesis in tl-'c corrcct posiuons'
ThcribosomcstartsrcaelingtlrenrRNAataSl'artcodon(AUG).Thiscodesforlhe
amino acids to the amino acid methioninc. Molecu'ics of transfcr RNA carry individual alongside a complementary surface of lhe ribosome. Each tl{NA lines up its anticodon
codoninrhemRNAandisboundinplacetotheribosonerr,hileenzymeslurkrheamino acidtothcprcviousoncitrtl.tcaminoacic-ieiluirrbypcpuclcbonrjs.oncciisjobisdonc, theIRNAreturnstothecl'roplasrntopickupanotheraminoacid.Theribosornemoves alongt}rcmolccu.leolml{NArcvcalingonccodonafteranothcrunulthcendisreached polypeptide chain' at a slop codon (UA.A^, UAC or UGA)' producing a complered Theansrvcrssho\rldinciudesomeorallof thefollowing.ot]rerpoinrsmaybevalid' TheyusedthemouldNeurosporacrassawhichhasashorrlifccycle,iseasilygrownand
.3 ts+c]
medium (with few murarcs easily.-I1e original srrain of rhc mouid could grow on minimal were exposed Moulds ncctled. and sugars it nuuicnrs) as it could synthcsise all amino acids
toXraystocauscmutadon.N4utadonsinthcchcmicalpathlvaystharaffectedtheability mutated slrains needed to synrhcsisc particular amino acids would show up casrly bccause rvould die. Crosses of they growth othenvise medium the to added one or more nuuients acids cou]d differenr sfains rvere carried out, to show drat dre ability to synthesise all amino that hypothesis the came and be passed on. From thc evidcncc of many experiments
return
a single missing cnzymc was rhc rcsuit of tl-ic mutadon of one gene'
4
enzyrne) for example Scicnrisrs recognised that rhc cnd result of a gene was not always an definition that it could be a structural prorcin or some othcr rypc of protcin and so the unraveued) wele proteins like hacmoglobin became broader, As rhe suucture of complcx scienrisrs rcaliscd thar sc.rmc prorcins wcre made up ol scvcral po$pepride stlands).and thlt ciilicrcnt rnrriarions changcrl diffcrcrrt polypcptidc strands which shcwed the gcncs protcin' rvcrc cociing ibr indivrdual polypepticlcs, not ahvays thc samc thing as the final
5
.iye now know rhat diffcrcnt proteins can bc manufacrurcd from the same gene, from *te evidcnce that.all r|rosc protcins arc alTcctcd by murarion in tl.rat gcne.We also understand of thar pos!-ranscripdonal changes may occur in mRNA, lrom observations of the action spliceosomcs. OtJrcr poinis may bc valid'
lldexccl A? Biokrgy Implcmcnration and Assssmcnr Guidc forTeachcrs andTcchnjcians oPexrsoo Educatjon Limiled 2009
irli:rj
i!; ::rt.lt,
Pages 78_81
I *
is the producrion of an anarysis of rhe DNA of an individual based on mini- or microsatetite groupings from a limired which can be compared with similar profiles from ou\er individuals. ""*b;;;;;;"ns
2
Used to produce a DNA profilc.
. 'lhe
srands of DNA
cndonucleases
I
*t i.h ,.o*
Dirrerent resrricr""
a sample are chopped into liagmenrs using resrriction
.il:::iliffi :::Hl J,",ff ,l,fi :::T ;::,*T:.
sequences knorvn as recognition sitcs rvhich are found ar cirrrer side of micro-satellite rrnits.
.
leaving repeatr:d
."r.,,r.,,..r',n,r.r.
The fragments of diffe f
ragmcnts"..pr,..ai.'TJ,I:T1T".J,:.;:::oJo:if
mainrain a consrant pH).
'
mini and
i:T;:i,:ff _Tl::J.:
The ger contains a dyc rvhich bincrs to rhc DNA fragmcnrs..I.hc dyc wilr fluoresce when p)ace d under LJV light, rv'ich _rt",
,1."'ON^ bands visible rvhen rhe .o*rno,r,r'ur.O ay. is EtBr (ethidium bromide). A different dye is also .aa.a ," ,fr. ONa samplcs to shorv the posirion ' electrophoresis is complete.
'
the sample s
..
uh.y
-ou.
Ti"
n-lor,
*uough thc
gel.
of
through
the appararus and rhc nNA fragmenrs *"::""i:"J:;:JJ::"',:"9 rherragmenrs_"".;.,"i;i.0.:.;X."J"ffiH:':;::f
.
DNA fragmenrs are usually placed in
a
move
;,n**l?:,i*:X
.;r;;i;;
.
When elecrophoresis is complete, the plate is placed under UV lighr. The DNA fragments fluoresce and shorv up .i.u.ly," be identificd. il;;; I'his is the original mcthod:f p"" fingerprinting, rvhich needs a relarively large of DNA ITslrowsuplargcDNarrrgmJnrs.r",rt,"r,mjninrunrol50basepairs,i.e. sample
minisatetites However smalrer regions DNA i;i;:sutcrJitcs) and specific genes can no\v be idcndficd using cxtcnsions "f o[ this t".t_ln;qu".
a
The porymcrase chain reaction rcpcats dre normar rcp)ication orDNA using the enz),me DNA polymerase. The reacranrs _ ,fr" OI,IA t"-0,"
polymerase, primers lsmatt sequences of
th' ,"p"."t.i DNA ,;; n u
cl
eo
d d
e
b
ase
s
_
ar
e
The reacdon mixrure
to be amplified, DNA DNA ,,uhi., mu:t join to thc beginning or
;J::":::::-:1\^ lvhr:h. f :'r: I Tf,' :l is{::J:jn:",: first heatcd ,o so-g5t i*.00r,30
;;ffi
:,e:*;,;h:
seconds which causes
DNA suands ro scparare as rJ-e hyilrogcn bonds hoiding drcm togerher break down. The mixture is then coo.led do*n to 55_60 "C anneal) to rhe singre DNA suands. r.rnuuv rh. ar leasr a minute,This is thc optimum ,.;;;;;; the
ilJH"T:::T:.r,"li:11."..,
w_hich
builds
ro .o,norn..n,a ry rands
'llhese three basic steps are
of rhe original
DNA,
s
re
or D NA
I
o";
:: : X
rcated around druuro 30 JU trmes rimes to
giit
::'#..,.fr
:round
1
:,:IiJ.
billion copies
Edexcel A2 Biology lmplementation and Assessmenr Guidc for'ftachcrs and rcchnicians opea.son Educadon Limired 2009
4 a
using Traces of biological matcrial are uscd as a source of DNA rvhich is amplified pcR and then used ro produce a profile. Because the chances of wo individuals having the same DNA profile are extremely low, when the DNA proflle of a of rheir suspect matchcs DNA tiom thc crime scene rhis is takcn as sfong evidence
involvcmcnt in somc
rvaY'
boniyidcnricallwinslrrr,cjdcnricalDNAprofilcs,lrcrlvcvcrfamilymemberdshorv of one many morc similaritics than non-rclated people"so, if rhe DNA of a suspect
will come ctime is checked, if DNA from anothcr family mcmber is on the database, it is not up as a close march. This can lcad policc to thc rigirt suspect) eve n if rheir DNA on drc databasc.
rcel
42 Biotog) Implement.don
gPcarson Educatioo and Assessmenr Guide for'lcrchers anC'ltchlicians
Liniled 2009
Pages 8z_83 2..\
+
' X UJ
Extemely small so can casily ger jnro rhe body. Sirnple s,'ucrurc of prorcin coar and gcnetic
harsh condidons and rerain
::i:."tr"r . '
matcrial mcans rhe virus can wilhstand
infecriviti
a.achnrcnr poinrs (VAps) ro cnablc thc'irus ro :rrr:rcir ro spccific tvpes of
Some have specific mechanisms lor injecdng rheir DNA inro cclls. Virar geneLic matcriar is adaprcd ro take over hosr cclr -..n"r;r;;. For example, direcdy as a temprare for borh neiv viral oNa ,.a i,,rre mRNAs
:::::Ti:::, #.il::::J,:'3"i:K:'
rranscrip rase is then used ,, ;;:;:::: a template
gcnomc.
I
RNA u""'
"irr corrcsponding
o'i,",r.*",',
or rcvcrsc
to the viral genome which lor :'^::i","^^ new viral proterns and ultimately a nerv viral RNA
Orher points may be valid.
ts p
tS+C1 'l}e answers should irrsluse include somc or all of the ibllowing. Other poinrs valid. mav be a Like living organisms, they reproduce, con genetic material' undergo obligate lnr...uurr. orrrlr"""r'""l"ll;.illtarn evolurion, are (can onlv exist and reproduce .r'o^..rti, in rhe celis of other living i
tr
";l:n:;*"'es
Unlike living organisms, drey don,c fecd, respire, excritc, movc, or shorv sensidvity The onJy characterisdc any ofriving *rings shorvn is reproducdon.
pages B4_85
L! tS+C1 The ansrvers should ,rLrucre include some or ail a. of the foilowing. . valid.
Other points may be
Lyric:virll gcne.c mrtcriar is rcplicarcd indcpcndcntly of r_hc host DNA straight glterir.rg th,e host celr. Marure ri^r..
afrer
u.. -i'. uy host ccll, which evcnruauy biiris ana numb.rs ofnew virus ou.,i.i.r.rnar. go on to invadc other virus is said to be virulent ' hosr ceus.The Cir.r,._.;;;;;;. releases rarge
Lysogenic: Viruses
r
gcr inro rhc rr.sr cc' 1hcy inscrr their h.,;i;lT:;:::'::;;::L':::.:':t *,t hosr ccll divides.No is produced t oth" DN; b;:";.". .7.3: 'RNA causcs thc producrion of a repressor prorein "i.-l which -"u;ii;|;rr;o:::"-u''"',4'n"s ffi ::t""3;::::,1:*"'"'ao'-,o".vi'I,,"'il:il::il.lilx'*il:t;::'"' Jiuons' r^ l*]j a Reroviruses have RNA ' as genedc
DNA inro ,n.
mareriar iniread of
b They
have more comnlpw tir^^..^r^by reverse
DNA.
nrst has to bc rransrared inro
DNA ",,.J;;::T'["j:fi:L::RNA into ,r,. r,,., o*a. v,;li 3",ifi:'#:?:l:.,i:::: ,:,i1" il:Ht,*:::erted proreins
^"0 Edexcer
42
"*.i,
.ilff
ll,T
ii}iliiivira
Biorog-y Impremcnrarion and Assessmcnt
I
m^NA
cuide fofTcrchers
and
ac
Lr;'
;,"*;::
l*,'"*,,i,"r
rcchnicians opcorson Educstion Limircd 200g
:'::il,tii rr'rii..,Ji
i;il'';llfj d!,'rnx!,nF{i$rr7f+f,.ttF!{@rtsjftlqiir:i:J@&ratrs,$t!LrKd6lfd&-8rs&1x\*F!}*F$r:!:titjwRl:rani*{}'Jst'It
pages
v
X^ '
86-87
/ R iS+Cl Thc ansu'ers shouhi
\)- points may bc vaiid.
includc sonre or all of thc following. Other compararive
5tructurai features
Animal cells
Bacteria
Average size (mm)
'10-i00
0.5-10
0.02-0-3
Cenetic materiat
DNA
DNA
DNA or RNA
Outer tayers
lipoprotein cell surf ace membrane
lMruses
cel[ surface membrane
may have an outer
and bacteriat cell wall made of
lipid enveioPe protein coat ot caPsid
peptidoglycan with
made up of rePeating
olher compounds
ca
psome re5
such as teichoic acid, lr
po
polysaccha
ri d es
may have slime capsule or lrytr
conta'nirB ater.al (DNA) ribosomes mitochond.ia Colgr body tysosomes vesicles cytoplasm cenrriotes c)'tosLeleton vacuoles endoplasnric reticulum (RER and
Main inclusions
nucleus
generic n
sER)
Movement
varie5
-
may not
I I |
genetic material
cytoplasm geret;c ma:e:'al {or'r.n)
l'PLasnids l'mesosomes I I I
I I I I I
I I
may have
i,agellae
move, may be
.
movement
I :il'.
amoeboid, may use cilia, fiaBelia, etc.
pages BB-89 ,i"r
li) a . b
Rapid, reiiable
(2'; z h tf
'r
\-/
-
can occur cvery 20 minutcs in
idcrl condidons
Brings ab<;ur gcnctic variation rvhich can cnablc bactcria to survive unfavourable conditions. shows that genclic material can be taken up by bactcria in
sflficient quantity to
bring about a changc in chrracrcr of the organism. and in this casc make it infecrivc.
b
Whcn rhc dead bactcri'a wcrc attackcd by cnzymcs t]-lat dcsrroyed cerbohyd-ratcs and proteins it had no clfect on t]re ability ofthc transforming factor to changc the R bacteria into S bactcria.This shows t-hat the uansforming factor is neither
carbohydrate nor prol.ein. However, rvhen the DNA is destroyed, the uanslormadon does nol rake placc, providing strong evidencc for DNA as the transforming factor. Edexcel
A,
;riology lmplementarion md Assessmcnt
i
lrlc for'lcachcrs and'l'cchnicians Ol)carsur l:ducaLion Limited 2009
90-91 *{ses 1L/ts+c] Thc answers
-**''"*w>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
fr..;i;:
Using chlorine_bascci disinlecrant ",". to be sure C. dirlic;lcis destroyed. Any otlrer valid points. ljdcrccl
n
2 Djolo!,y lmplcmcntario
I
3nd Asscssnrcrl
6uidc for-ltrchcrs !nil.Ji.clttic;rD3 cl,(,!rsoo Educarjon Limilad 2oo9
Pages 112-115
1
Natural activc immunity: Inlcctcd by pathogcn rvhich mry rcproducc and cause 'sylnptol)ls of discasc.'l-lic inltlurtc sysLcm is lctivatcd unrl thc imnunc.cascadc iniriatctj: B cells, antibodies andr cclls produccd rvhich dcsuoy parhogcn. Immunological memory et-rsurcs that if the pathogen is mct again, *rc immune systcrn is acdvated before disease results.
Natural passivc immunity: Anribodies against various diseases are passed from mother to baby through placenta or in brcast milk- Short-tcrm protcction against these diseases as immunity is losr widr time,
Artificial passive immunity: Antibodics produccd in onc individual or animal are given to anothcr individual if drcy havc comc into .onto.r ,ultl, a panicularly dangerous or rapidly acting pathogen, e.g. letanus. Short-tcrm protection as no immunological memory involved.
Arrilicial activ€ irnmunity:'ll.rc immunc sysrcm is cxposcd ro rlrc attenuated pathogen (e.g, dead, inacrivared toxin, attenuated livc organisrn, protcin coat fragment or DNA fragmenr).This srimulates rhc immune rcsponse.The immunological memory ensures that if thc live pathogen is encounrcrcd again, B ccils,T cells and antibodies rvill deal with it bcforc it can causc symproms of discase. For cxamplc, vaccination against polio, rvhooping cough ctc.
2 Astlreantigenporrionofvaccincbccomcsincrcasingiypurc(bitsofproteincoat,DNA .
fragmcnts ctc.) somct-hing clsc is nccdcd to srimLrlalc inflammation and thc full,blorvn - researcfi into best material to use. Anv other valid points.
immune response.This is thc rolc of adjuvants
3 a
'l'l.rcy arc l)ot inlrnunc [u drrr diseesc, thcrclbrc if thc5, nrecL drc padrogen in aris counuy or abroird rhcy are likcly ro become iil and may be permanently damaged or die.
b Ila
child is not vaccinared, ir may carry infcction or become ill and put other unvaccinated children (e.g. those allergic to eggs or rvith compromised immune systcms) at risk of the discasc.
c'
From anindividual point ofvierv,completely ethical. In lactircouidbercgarded
as
uncfLical if parents did not have a choice o';cr rhcir children,s treatrnent.
'
From a socictal point of view, it could bc argued that it is unethical rhatindividuals tluough ignorarlci, misconccptions, laziness or indiffcrence could compromise not tlnly rJrc healdl of tllcir orvu cirildrcn irut also thc hcalrh of socicty as a wholc und the rveakest membcrs or it by tlucate ning rhe cirnccpr of herd immunity. So from ihis perspecdve it is unctrricar that parents can deny rieir child immunisation. Any orher valid poinLs.
I-'i
r\ccl A2 IJiolon' lnrplcmenlrtion rnd Ais,:
, rn
cnr Gui<]c Ior -lcrchcre and
ltchnic[ n. ,! I carson .Lducrrion Limi
rcd zoog
4
A link benveen the whooping cough vaccine and brain damage rvas suggested,The rncdia took hord of tlrc story irrLl publis'cd ir, rrut ig.orcd drc rnct rrrat whooping cough is known to cause brain dam"ge in some chiidren rvith a quandfied risk. parenrs panicked when they heard the-srory and didn't rake thcir ch'dren for vaccinadon wirh the rvhooping cough raccin". More childrcn *rr.t"d ,uff".ing from
whooping cough and cases bfdamage caused by the disease began to be seen again.The scare was shown to be no more than a correladon which had caught the eye ofa doctor rvho became convinced of the problem, in spite of a' evidence ,o ,h" It took /ycars !q' ! rvr for public confidence vuu'e uur "onou.y. in the vaccine to be restored, Materiar on MMR
as
produced by students.This shourd covcr
hor,r,concerns over the NIMR vaccine came about; rhe efrecr of rhe media and how the story rvas reporred, including the rack ofscientific analysis in rhe reportingl the response ofparents; and rhe impact of thc rcduction in takc-up of rl.rc vacci.c on ['c nunrtrcr of cuscs of mcasrcs, mumps and rubella, including their worst side_effecrs.
pages 116-119
1 . t is uansmitted lrom one pcrson ro anorher by droplct inlccrion. ' It can aflect a wide variery oftissues, bur pardcularly infecrs rhc lungs is easily coughed out and spread. . ' It has evolved a protective wax outer covering.This allows
rvhich means it
bacteria with the random mulalion rvhich providcs thc tirickcst ourcr co:.lr ro ror vcars unr'trre nort i. i,' a ro,v rcsponsc, at which point thc hrcrcriu can trkc Ir,ll,l rncl bcu,rmc ire rivc.f1165g bactcria bcst {incd for surv.ival in drcsc co.rliLions ura t]," un", rv'iclr rvill bc passcd on. Anacks the immune system of the host and so red.uces d-re delences against it. * has evolved resistance to mxny of the most commonly used antibiotics, rvhich means it is more successful at surviving and spreading easily.
phvsicarc;;r',J:li,,lrT':::::.Til;'jJ""'*'t
' ' 2
Primary infecrion: oftcn sl,rnpromless but causes an inflammatory response from the immune system.The
immune response forms a mass dead bacteria and macrophages uapped in the cenue u,here conditions are completery anaerobic After about cigrrt wecks trrc immunc systcm controls the urL ilrvcuoacterlar mycobacteria, the inflammarion dies down and the lung dssue heals.
"rrirr;.-;;il;;;;;il,.,;,-
Active rubcrcurosis: the bacteria mrrlriply r*pidiy ancl dcstrpy r'c )ung tisstjc. symptoms includc fever, night sweats, loss of appetite, loss of weighr, fcciing tired and listless. As rhe infecdon invades rhe lungs, it causes a cough. As r-h. clugh ,"._";r., Uil.:; Iungs bccomes damaged and btood may be coughed ". *" ". ,;;;;;;.,;";*., the tungs is stead'v destroyed, "oln rvith the arvcoli b-rcaking dorvn to ,ril;;;;., ;.r'.,.n, air spaces_TheT cells of the immune sysrem are ,ff".,.0 so antrbody producdon is rcduccd'
Evcntua'yTB causcs dcarh, ciLhcr bccausc Lhc inciiviaLrar c'.nor gcr cnough oxygen from the air tluough their damaged lungs, their organs f ail *Lrough lack of nutririon, or *rough opporrunistic infections such as pneumonia.
Edcxccl A2 Biology Implemenbtion and Asscssmcnt Guidc forTeachcrs and Technicians Opcarson Educadon Limired 2009
,_:
.:::
3
[S+C]
The
valid.
. .
Povcrty: malnutrition thcrcfore supprcssed immune svstems making infection easier,
'
High rates of illncss frorn malaria, watcr-bornc discases ctc, so immune system undcr
Crowded living and r.vorking conditions: ease of infccrion. prcssure.
'
High rates of HIV/AIDS so the immune sysrem is inacdvared, making opportunistic infecrion easicr.
'
Poor infrastrucrurc and limitcd mcdical rcsourccs, so lack of vaccination programmcs, lack of accuratc diagnosis and lack of drugs r.o tlcat symptoms cffectiveiy for the dmc requircd.
. Catlc infectcd 4 [S+C]
wi*r bovineTB and milk not pastcuriscd.
Thc ansrvcrs should includc sorrc or al] of
ti-rc
following.
Any valid points, well-argucd and rvell-rcsearchcd matcrial, showing awareness of the conflicring perspcctives of scicnlisrs, farmcrs, poliricians, tlre general public etc. pages 12O-'123
1
Initially alier infccrion pcople may have lcvers, hcadaches, riredness, and swollen glands but may have no symptoms. About 3-12 wecks after infecrion, HIV antibodies appear in the blood so person is I-{IV posirivc. oncc rhe infecrion is esrablished, au symptoms disappear and this stagc may lasr many years (in fit young people with access to effective anri-AIDS drugs), or months to years (people with litrlc food or medicine). During dtis sragc drc virus rcplicutcs, infccr-jng drc CD4-l:hclpcr cclls but is kcpt in cficck by drcT killer celis.This is rhc sragc whcn othcr peoplc may bccome infccred *uough hlgh-risk behaviour. E*cnrualiy secondary infcctions devclop as the irnmune sysrem begins to be overwhelmcd and symptomaric disease returns.The viral load becomes so large rhat the immune system can no longer cope.The normalr:heiper cell count falls Iiorl 500 pcr mnr3 of biood ro about 200 pcr rn*3, and symptoms devclop including weight ioss, fatiguc, diarrhoea, nighr swcnrs and low-gradc infections such as t]rush.This rapidly progrcsscs to the final stage. As thcT:hclpcr ccll numbcrs fall, scvcrc symploms bcgin to appcar such as major weight loss, dementia as brain cclls bccome infecrcd, canccrs (e,g. Kaposi's sarcoma) and serious infections such asTB and cryptococcal mcningiris.These scrious diseases, along with opporLunistic infection, such as pncumonia lead to dcarh.
klc:ccl A2 Iliology Irnplcrr,r :tation and Asscsvncnt Guidc for-I.rcbc:! :nd Tcchnicjans opcarson Educadon Lii, :.d 2oo9
, fU::,
Thc answers should include somc or all of
rJle fot)orving.
Orhcr points may be
TB: Bacterial; infec* a wide range of cells, including lungs, lymph and bone, as weli as macrophages of the
ir
rvi&inthe,";,,0"..;;-:!:!:#Til;lili.iiff
::ilfi#.::;:::,::,0'-*'to cured by
rungs o.
:::,"J:T:fi :J.",".:,"?,,fi ;'.",', but arso
-^rn,,t irio,,
anribiorics;.r.i'#:T.T;*;iTffiilcm;
reaves body
oo",,,o
can bc trcotea effecuverv anrl
HIV/AIDS:Viral; infects the helpcrT ccils of trre immune systcm; .sv*^tr. ori^afler :_:^i initial, infecrion pcriod rcmains dormant rvirhin rhc inrnrunc ,rr,",r, ,.lun. a pardcurar ser of svmproms bur rhemain imiacris vulnerable to a w'ide range of opporrunisdc inlections which usuai)y resurt in death; the course of disease can be slowed bur nor
J;:H:::,i1.iilil;iilll1,
prevenred uv
vaccine.
3
;:;;.,,*
Main mechanisms: rhe rhick coat of M. ttberutbsiscnabies *rem ro survive ins.ide macrophages for many orrtl dormant o, ,10*-g.o,uing srarc.This is the resu* of '.n.r thickcsr
;:l:::::T,"T::,_.,*.?" evolution.
coars survivc
aJd wiil be abrc ro inrect other hosts, :ssful pathogcns. Multidrug-rcsrstant srrains are also the result
ltfiTf.Htil.T:(and '
*.oi.uJo,i'; il
rhcrctbrc cvolurion) mcan changcs in arrtigens which makes virus' The targetting ."u,
J.
of
or immune svstem fighting the virus' Rapidly antigens makes vaccine productio' evolving very dilficult. Some pcople have genes which make thcm rcsistant ro Hrv. Jn counries where the wil bccome oo,-,.in"ni i* u'iopuradon as individuars with them
reduce'"T:lr:iil.T,:"#;::},i
:iffi: :T:,::::::*'
Edcxcer
A2 Biorogy rmplemcn.rion and Assessmeot Guide forTachers 3nd rechnici!ns opqrson Educetion Limiicd 2009
Pages
{ lj -
128-129
It supplics energy in thc forrn of ATP lor all ccllular reacdons. ft also supplies subsrates for othcr metabolic pathways, inciuding amino acids and larty acids. strcngths: succinct summary; sums up thc nccessary rcacrants, rhe desired product and rhc waste products; gi'cs a balance chcmical cquarion to shorv the proportions ofrhe reaclion chemicals. Limitations: shows it as a singlc reacdon, when it is a complcx series of reacdons; doesn,t show wherc in the pr-ocgs-s ATP is made; gives no indrcarion of the enzymes involved; thcre is no indicaLig6*H@ff*{vc substrrles can bc uscd; thcrc is no mcndon of hydrogen acceptors, coenzymes Etc. Any other valid points.
pages 130-131
Q a Resliror.,"t"., *"ur.,r.
carbon dioxide output and use rhat !o calculate oxygen uptake during respiration. Looking at the whole organism, ir gives an overall picture but no detail olwhat is happening in individual cells, e,g. u,herhcr the carbon dioxide comes from aerobic or anacrobic rcspiradon. Any orhcr valid point.
A-
'{ (T) lfne apparatus rvith rire two tubcs rvill givc morc rcliablc cvidence bccausc rhere is: * " " clcar scale to mcasurc changcsl syringe for recafibiarion; KOH on bot]-r sides to
eliminatc drc amount of carbon dioxidc in normal air lrom the results. Anv orher valid poinls.
@
Euidan." is ncedcd to associatc rhc subsrrare molcculcs or enzymes involved in a particular stage olrespiration wi*r the mcmbrancs or the contents of a pardcular area of a mitochondrion, e.g blocking or poisoning of one mechanism and observing the buildup of product in a parricular arca of the roitochondrion.
pages'132-135
'
1
During vigorous cxcrcisc, tnusclcs rcspirc anacrobically, producing lactare which builds up in muscles and is carricd arvay in the blood.Whcn cxcrcise stops, as well as the normal oxygcn dcmands of the body, lactate must also be oxidised 1o pyruvate and g)ucosc in thc livcr,,{f i'] and phosphocrearinc rcvcrs nced to be ,"rro..d, myogrobio needs rcoxygenaring, and metabolic rcaction ratcs are faster due to raised temperalure using more ATP. So r-he oxygen demands of thc body rcmain high for some time after the complction of the excrcisc.'l'hc rare of brearhing continucs to be raised to suppiy the necds of the body and t.he hcart ratc rcmains high to pump extra oxygenared blood around rirc body and rcmovc thc cxccss carbon dioxidc.
2
Diagram similar to fig.7.1.6 wirli anr.loradons such . Glucosc, 6C sr:gar, is starring point.
as rhc
follorving
. ATp uscd ro phospl.rorylarc
glucose _ 2 phospharc groups added to give phosphorylared 6C sugar, onc reacLion conrrollcd by pi:,osphofructokinase, rarecorlLrolrirg rcacLior: Iirr l.c wrrorc proccss of cctular rcspiraLion.
'
Phosphorylated 6C sugar split to form 2 moleculcs of 3C glyceraldehyde-3-phosphare
(GALP).
W
rdc-\ccl
'\2
Biologv lmplcmcnlarion and Asscssrrrcr:' Guidc iorTiachcrs andrcchnicians opcar ,
r
Educarion
Limircd 2o09
Each molecule of GALp converrcd to pyruvic acid in a serics of steps _ lor each molecule of GALp 2 hydrogen aroms removed to reduce NAD which is passed along clecuon uur.f../t
":,.,":i':T'"r:::;i'Jf "r*..1; :T:::11""-toproduce'-",..'l-,'"Lirl,1'::'HlT?:,i:: i'irial phosphorylarion
The
reacdons arc reversed before rhe finar intermediare is pyruvlrl.c ancl drc |)rosp)rirtc grou]) ,.t.,,r..t ;, usecl ro proclucc A1_l)
;#H},,"
2 molecules ofpyruvate enter mitochondrion and go into Krebs cycle for every glucose molecu.le rvhich enters glycolysis.
. If insufficient 3
oxygen, plruvate con,.,rrteC to lectatc o:
erhlnrl
During the proccss trvo hydrogcn atonrs arc rcmovcd from r'c 3C sugars and taken up by NAD to form reduced NAD rvhich ,f_,.n
.nr.r,
,f
energv which is used to phosphorvrate 3 rvhen rie 3c sugar is converred to pyruvate. This rcplaces thc ATp uscd up ,o to p, prime rhe 6C sugar, and the remaindcr is available o, ur"iui.n".r^;" crgy lbr :,::^:^,::,:p ccll metabolism, assuming that the substa,. -.r.. on into acrobic respirat.ion.
.or..ur.r;;;s;T;;il:i';:T il:H*
pages 136_137
1
Giycorysis: doesn't need oxygen ro produce ATp; linear; rerarivcry simpre; takes prace cyroplasm. Any othe r in valid point.
Krebs cycle: needs oxygcn ATp; cyclical; complcx; rakcs place in ll.produ.." mirochondria. Any odter valid point.
2
IGcbs cycle alonc docs r e d ucc y p ro cl u c e s J:i; ir,T:
c y c
r
r
H::::::*il':;Hn:'"'o"t I
tS+Cl The
valid. Itebs
i
::i
,-:
::1,,.::
lllill ti,li
filli
fl : : Xh chain' which in turn rereascs encrsv rhar is used to drive
ansrver should includc ,lLruuc somc or ail all ot of thc following. other points may.be
used enzyme
re s u r rin g
:ffi?;
n a bur
a
inhit.
-up
il"J:.,".:::: ;ff
:11:
;.ffil;; il
;S:#**
:1":: comparcd to an anarysis of the normal process..This cnablecl Krebs and his team of scjcndsts to work out exacdy rvhich chcmicals r*i"*,*u in a particular stcp of thc process. Answer could include diagram of appa.arus used. pages 138_14.1
t ::;",
The ansrver should include somc or all ol the follorving. Other points may be
Diagram should show all stages of aerobic rcspiration: grycolysis, link reaction, cyclc and elecFon transport Krebs cl.rain, u
making
al"r, ,ulor.
..or.J'o;3,,.:lH,Jfi :ff t..?':::r. inai.",,.n n"; ;;;; :: I.ffi :.::,r; i:::f:$::ii1 -,, ", bc inclutlcd' clariry
sed and formed,
*r,lr.?ar,."a NaD
and
iHil:iilimportant.
diagram is
Edexccl A2 Biology lmptcmenetion and Assessmcnt Guide forTeachcrs
;;
of layout of
e ,d Tcchnjcians Op.arson Educarion Lihilcd 2009
2
The oxidation ol glucose is a muiri-stcp process during rvlrich rhe glucose molccule is splir inro 3C unirs, builr back into 6C mole cules and thcn dismanded again. As hydr.. ;., is rcmoved,
it
is used to reduce carrier moiccuies that pass to dre clecuon transport ei:,':;r.
As the components of the chain are reduced and then oxidised again sufficient energy
.
3
production of A"I'P. By the end of rhe process glucose has complctcly oxidiscd to crrbon dioxidc and rvatcr.
is releascd to drive thc
bee n
Glycolysis (at the start of acrobic and anaerobic rcspiration) has to expend ATP to move re duccd NAD into the mitochondria to reach the electron transport chdin; one hydrogen is removed frorr cach 3C sugar in glycolysis,while 5 hydrogen atoms are passed into thc clecron uansport chain from each 3C pyruvare molccule that enters the Krebs cycle (acrobic respiration only); acrobic rcspiration involvcs completc oxidadon of glucosc
while anaerobic resuhs only in its partial breakdown. Any other valid points.
4
Energy from electrons as thcy pass alcng the clecuon uansport chain is used to acrively transport hydrogen ions into thc space bewcen the inner and outer mitochondrial
membranes.The hydrogen ions cannot pass through dre jnncr mitochondrial membranes. So a conccnualion gradienr lbr hydrogcn ions is buih up ilcross rlrc inncr membrane.This also creates a pI{ gradient and an clccuochcmical gradient. Aldrough there is a tendency for drc hydrogen ions to movc back into thc mauix, thc only way thcy can move back is *rrough special pores.Thesc porcs arc found on dre sralkcd parriclcs, and ihe movement of thc hydrcgcn ions *Lrough drc porcs is iinkcd to
an{l'Pasc cnzyme.The cnergy ftom thc
gradients is used to drive rhe synthesis of ATP. This modcl is important because it provide, a mechanism for the observed cvcnts in a rvide variety of cells, and it shorvs how the removai of hydrogcn atoms from glucosc molcculcs can rcsult in the production
ffi
Edcrccl l'.: iIi.logl,ImplemcnlaLior, and Assessmcnr ( L dc forTcrchcrs indTccluicians OPcrrsoii Jliiucadon Limircd 2009
oIATP
Pages 142-143
1 vhole muscle
is made u p of m any mus clc fibre s. Difrere nt libres :night have different duesholds for response, or dirfercnt levels oiresponse, so whcn the rvhore muscle is stimulated the contracdon might be more or less than expccted. Striated muscle
5mooth muscle
Cardiac muscle
attached to the skeleton
not atiached to skeieton
not attached to skeleton
involved in locomotion
involved in moving food through gut, controlting
pumps btood out of heart around lungs and body
diameter of blood vessels etc. controlled by vo{untary neruous
controLLed by involuntary
svstem
neryou5 System
ccntracts spontaneously, some voLuntary and involuntary control
striated appearance under microscope
no striations seen under microscope
contracts rapidly
contracts slowly
average around 70 contractions a minute
fatigues rapidly
latigues slowly
does
striations with cross connections seen under microscope
nct fatigue
jages 144-147 '4"
respiration takes place in rhe mitochondria supplying thc acrive muscle cells with supply. Myoglobin is a protein similar to haemoglobin, with one chain rarher than four, rvhich binds oxygen ancJ has a much highcr affinity for oxygen than hacmoglobin' Myoglobin readiiy acccprs oxygcn fronr drc blood und acrs o, on.r^r.g.,, store in *re musclcs.
'J l::bit A I I' as an energy
. e ft
Fast rwirch fibres havc ic,.-m1,'c!og: and liulc myoglobin: rhcy produce a quick burst o[ aerobic energy then anaerobic respriition conrinues: rhey farigue qui.tty. sto* wit.h fibres have many mirochondria and plcnty of myoglobin; rend to have a rich blood supply bringing oxygen which is taken r-rp and srored by the myogrobin; atow plenry of aerobic respiration over Lime .
ps9 ^'
Lee muscles contain lots of srorv nvitch fibrcs, wirh a good brood suppry and lots of myoglobin. Therefore these muscres are a dark colour, contain lots of mitochondria and so provide sustained activity for walking around but less speed and power in initial contracdon. Breast meat contains more fast wvitch fibrcs, rviu\ rclatively little myoglobin and lew blood vcsscls. Thcrcfore drcy arc a palc colour, goocl for short cxplosive bursts of acdvity such as a shorr flight.
Edexcel A2 Biology lmplemcnlation and Asscsrncn!
cuidc forTeichrs rnd']'cclmicirns opearsod Ed,ucaliotr Limitcd 2009
'{ tS+Cl'lhcansrvcrshouldincluclesomeorallofthefol)ouing.Orherpointsmaybegalid 5[ow twitch muscles
Fast
deep red (lots of myogiobin)
pate pinUwhite (little myogtobin)
lots of capiltaries
few capiLlaries
{ots of myoglobin to store oxygen
little myoglobin
not much stored glycogen
large gLycogen stores
littLe sarcoplasmic reticulum
lots of sarcoplasmic reticulum
doesn't fatigue easily
fatigue easily
many mitochondria
relatively few mitochondria
twitch muscles
P€ges 148-149
L
Diagrams as in fig. 7 .2.7, fully labcllcd to show rhe H zone, I bands, A band,Z lines, actin and myosin {llamcnts.
2
Calcium ions rclcased in rcsponsc to nervous srimulation o[the muscie set up conuaclion of thc sarcomcres. Calcium ions bind to uoponin changing rJre shape of thc molecule. This changes t1-rc shapc of the ropouin mo)eculcs, so'&cy pull on *re tropomyosin molecuies ro which they are arrached.T'his moves the ropomyosin arvay from lhe myosin binding sites on the acrin moleculcs, exposing rhcm, so thar rhey can bind with the myosin heads which sets up the conuaction. Calcium ions aiso needed for the acdon of *re ATPasc enzyme in tfrc myosin he ads, rvhich e nables rhe heads ro renJrn to thcir resting position.
3 a ATPbindstorhemyoglobinhcad,andthereleascofenergywhenitishydrolysed ailows rhc hcad to rcturn ro rhc rcsling posirion.Thc bonding of the ADp and Bhosphate results in changes in the shape of rhe myosin head so it can bind to the actin binding sitc.The release of rhe ADp and inorganic phosphate resuhs in another shapc change rvhich rcsults in lhe rclcase of the myosin head from the actin binding sitc. AfP is also nccdcd as drc crrcrgy supply for rhc carciurn pump wrrich returns calcium ions to the sarcoplasmic rcticulum, ending the contraction.
- iroganic
b [s+ c]
The answer should includc some or ail of thc follorving. other points may be
valid.
Aftcr death, once there is no more ATP, the myosin heads cannot returftto the resting position but remain lockcd upright, so rhc muscre bccomcs stiff and rigid.
pages'150-151
C
l'jdcxccl A2
ffi_
SVnovial fluid is produccd by synovial rnentbrancs
i. joinrs *,ith biggesr range of movement. It acts as a lubricant bctrvcen thc cartilage covcring thc ends of the bones. Prcvcnts wcar and tcar o[ *rc crrriirgc.
Biologf Implcmcmation and Asscssmcnt Guidc fo.Tcachcrs anrlTcchnicians c)perrson llducarion Limilcd 2009
._,***"lwssec**liiiii?;ni#siffi#"{
/l .p 4 (:/' '
sones; form the lramework and support; hard, suong dssucl act Ioinr".\,,L^-^ Joints: rvhere .-two bones mcet; allow ; movement.
ljii,fiT;Tiil.l:ff:::::"::lrhe
as levers.
joints;hord
boncs uonc.s in rn ptace prace so they uscful work withour rhey can do becomins.""":;,'";,':;::':ru to Lo be oe elastic erastic to allow the joint ro move ruh", auow the J. bones n"."rJ^.." .,^;^:'^,::."tuu 1':'".:d -;;;;;:::"t":::l.l?,t^'.1, -r":r'L rrsstrc grvcs s,.c,,srh rvith tightness of capsules ' crasticity; ", varies rvrth movement needed in joint. "r r,. Muscles: provide the power ro move rhe joinrs; Ur_r. :;; conuact and relax; are attached to bones bones by bv tendons fenrJn.o *hr.h rr,L,i^L r-.,,i^tt:-'n"o confaclion of the muscle is converled into t,dub as u.rey can onJy pull, so muscle moves a bone in on :1 i:Te."'sl; one and when ir rclaxes, anorher muscle puuc rhe bcne back to iis orig.inal orisjn:l piace, .,,":ir..,ion
i*.,
,
";o;i;;;;;iliil':::::::]'::'-',"'::'".'lvcs
moro*^., ff :J:T::fi"#J;:::: :::::
;;t ;;;;;, i";l
il, ;ffi :::::1,i:il::'::.
Any othcr valid descriptions, diagrams erc
Edexccl A2 Biology Implcmcnurion
ud
Assessmenr
Cuidc forTeachc.s qnd Tcchnicirns Oparson Education Limitcd
2OO9
ri:]i!"':i+i
Pages
1
52-1 53
1
The natural pacemaker should send impulscs regu)ariy through rhe conductivedssue of *rc hcart to thc vcntriclcs ro rigger thcm to conuact and pump blood out of the heart to the lungs and around lhc body. I3y dclivering elecuic shock to the ventricles when the SA node fails, thc artificial pacemakcr uiggcrs conrraction in rhe ventricles and replicares the intrinsic rhy*rmiciry of thc hcart bcat.
2
P wave:
clccuical impulscs uavelling from SA nodc.
QRS complcx: wave of excitaLion spreads from rhe AV node and through the ventricies.
T wavc: recovcry of contrrcrilc
*rough the bundle of His
tissue and rhc vcnuiclcr.
pages 1 54-1 57
1
normal blood pressurc
*
cxercisc raises blood prcssure
detect rise in blood prcssurc
in brain
-
*
baroreceptors in carotid arteries
ccrdiov'Jscul?r ccrtuc scnds ncrvc irnpulscs to hcart and blood vessels
ratc slorvs and blood vesscls dilate
rcsl excrcise
7
-
barorcceptors send ncrvc impulses to cardiovascuiar centre
-
+
heart
blood prcssure fails back to normal.
re(overy
70
:i
€5
ro 5
10
Time/minutes
3a
At rest
Vigorous exercise
6000
14000
14000
'12000
1
12O00
10000
10000
800
800 500
600
400
400
?oa
200
0
0
o"r*
r.*l*ob".{-tt".".rt.r+' +t *€ .
v*. -".b \n' ^S' .I?
"+*
*d
Cr'.i_*+'".|'''{o-{.,o"o;ir"e \$
os
^,."
Blood ftow at r€st
ffiffi
fmm-Fn-ls
.g$
Elood flow during vigbrous
I ffi Sl
$
frl El
mrcise
heart tiver adren4l g{ands brain tung tissue
il
kidneys
l-i'l kidnevs
&l skeletal musclcs
[ fi Edcxccl
A2 Biology lmplemcntaoon md
Asscssme
o"'
qY
5kin
other parts
nt Guidc for'lerchcrs md'ltclnicians opcrrson Edusdon Lifrited 2oo9
El
S
hearr liver adrenal glands
Sl brain B! lung ti$ue El skeletal El siin
$l
rnutcles
other parr
During exercise th
*r r;::,T:i:;:*:".ii:::::; :,i the b,ood supp,y is shifted rhe :::m*,,.#ffi j ffi i H::: ffi n:Tff l.i,' ;:H T:,J:,"T_ bloo j o.* ;;;; and ;;;J, ." o illilT|";,::T::: :T:J:oxygen "",ood into the";;;; the skin also increases body,. Blood now ro rhe imporraut. BlcoJ
b,ood ,o
4
,.,'
s
*."r,","1"^^.*^rr:ure
Nervous controi: involt n_ervcs srow ir down;
lflccr *rc aO* cardiovascurar rv
hi c h
ar
e
a
heart rate
""O
as
,"o,.
sympathetic ncrvcs specd up
herrt rare, parasympatheric n.'ntutt' come from cardiovascu dJalar ccnrc; impuiscs lrom Lhese nerves r"l."es *. .nrur- o"ii
il,
i.h"nr"
".nrr" o, ;,0;": ;.1T: :,: :_.:_,..:,1
rre c r e d
r..r*.;l;;;J..Iffi ffi'#:.l,.".l" exercise;;,;;,;,,'-:"'":::::::'n
baroreceptors
irnportant
florv to
-l*lll.'.T;ii#::*:.lllJ il;,ll':.J; ffi il".',,I,.
j:ffi:::Jt**::surc
il;il.
:;: l,:: : il: n"j ff : " hearr as .*"..i.",,".* !h,:
carbon
n::k,rvhich
t
o.,.0.,
is parricurarry
dio*',. ,,' *. ol"io'"i," .o..,
Voluntary conLrol: - nervc '^-' ' JS from conscious parts of rhe brain can arso t'e srimulate or inhibir
sAN.
Hormonal conrol ;adre stimurarcs rhc SAI{. hcarr so it bears faster.rnt"n. td more Anv othcr varid points
s
'";';;;;;;:'l"i';i:lrlr;:'""'""
rarc
ortre
pages 158_161
I
Spiromctcrs can bc uscd [o mr,rcrr",, tr,.. r.__ .t $s lrrcadring I'rt r-he
r'*r; ;;" *'u'i'":t:'l':..:: "t:mcasurc 2 IS+cl The answer rnor""ount'n'o'"'*' Also,
D agram shou,a in.,ude
:i,
*il ;m
Edcrcer
:; :
ife;::::j:ffi:
;:::d-: ;il"-::-':::,,,.
:;H t* :i:i1;ii:T:
42 Biorogy Imprcmenkrion
and Asscssmeor
arr'l rvhilsr cxercising etc'
T,;
';:'"T;
:
ill+ri: lTffi cnuoned dircctJy or by
. r d b. d
es
association.
cuide for,oachcrs rnci rechnicians opea.son Education Limired 2009
;
id!:i 3CarbondioxidelevelsintlcbloodincreascrvithexerciscaSmorecellularrespiration fall fail as carbon dioxidc concenuarion goes up) and rakes place (and pH levcli lvhich
ashardbreathingcontinuesafterexercise.l-evelsaredetectedbychemoreceptorsindre oltirc ncck and the aortic bodies in hindbrain, rhc carotid bodics in tl'rc carotid artcrics
rhcaorta'Tlreyrcspondtochangesinlcvclsbychangingdrcratcofimpulsessenttothe impulses to *re intercostals muscles respirarory cenue in the brain, rvhich in turn send
uni th. dirphragm to
change the rate and dcp*r of breathing'
srimulates the respiratory cen[e to Brain cortex: recognises movcment has begun and cause an increasc in brcathing rate' and in thc lungs mcasure the dcgree of Suctch rcceptors in musclcs rcgistcr movcmcnt)
stretching,andrespondwirhimpulsestotherespiiatorycenfetoaffectbreathingrare' Voluntarynefvescanbcusedtoincrcascordccreascratcordepthofbreathingwithin reflcx kicks in' boundaries, beyond which the normal breathing
Any otJrcr valid suggcstions
4tS+Cl.lleeansrvershouldinc]udcSomcola]lolrhciollow.ing.otherpointsmaybevalid. For:bcstwaytocollcctdatatohc.lprvirhucetihgbrcathirrgproblcmsinotherchi]dren; Iesponseinchildrenisdifferentrotheresponseinaduits,socan'texuapolatelromadults from ir)'
(aud probably got a lot ro chilclrcn; children involvcd enjoyed rhe expcrience put children at risk urulecessariiy; they Against: could have bcen v.cry risky - not right to a good reason to do it; conditions not so rcscarch rvcrcn't benefitting dircctJy {iom rhc wcre cxlreme and onc chiid srugglcd with thcm'
pages
162-163
lMctabolicreacdonsproduccheat.Duringcxerciserhe}evelofaerobicandanaerobic of hear produced increases respiration in dre muscles incteases so the amoun! and damage the metabolic cruymes denature can considerably. High temperatures internal tcmperature by conslant rciltivcly oI Maintcnancc proccsscs thcy control. the core body tcmperature from swcaling, skin flushing and so on is vital to prevent
risingtohighcriticallevelswhenpositivefeedbackmechanismsrespondbyincreasing m:king temperature rise until it may the metabolic rate so proclucing even more heat and rcach lcthal lcvcls'
2[S+c].lhcanswershou]dincludcsomcorallolthefollowing,otirerpointsmaybevalid. Srengths:givesdircctevidcnceofindividualhumanrespclnsetochanginglempelarure; indicatc cffect ol changing can control conclitions qurrc closcly so thet rcsults clcarly condidons. studied; takes a long time to Weaknesses: not parricularly comfortablc for person bcing
cojlcctdataonalargcnumbcrofincjividualsinmanydilfcrentconditionsinorderto Produce rcliable conclusions'
ISdcxccl
andTccluricirns oPcarsolr EiluceLion Limited 2009 A2 Biology lnplcmcnrarion anrl Asscssmcnt Guidc for'llrch$s
pages 164_167
t
increase due ro muscre activiry and
;
llilTj::J,".,,T:Tj:j:i:,:j.:llerarure,wu ck ;. ;' ;; ;::: lost heat :: j :::: ::1evaporation, I*' 1* rcandd increased through i e
.
".";";;;;";""
;;:: blood
b a
ifill};r"*
j:
J::::,1'
il'J, ;rng so flow to surrace orskin means "n.*,o* :
Drinking ice cold water can cause problems because ut, ,.,_ra, to drop the blood p'o'r u.."'r bv mu scrcs'"u n*"'
ilTil:*:il
:11 i:':: "'"i""1*.,,.. hear,",. or,,*,,',jl::T:"ffi."rH?J;:::""'"'.rion orbrood vcssers in skin ro rise again as a res,* of themetabolic heat so the
i.#:::::
reduce
rrr;::Tr:T::ili:::l;:::::.:
2
but it wr'uid take ir-:ngcr to rcstore rormal core body tempcrarurc. Any other valid points. Thermoreguladon is not as effective in elderly peopre.as brood circularion may be poor. 34'c is a hilh temperarure and so rhc man *'i ,oo, gct hot borh from the externar temperature
and the exercise. A raised externar hear rhrough conducrion' He couid n"*
,"*f
makes it harder to losc body ".orr." o-Jt.-, iirh thc negadve feedback sysrem proronged walking as means.prolongcd e*..rs h..t - exercising in heat wi*r thick rur coar can r."a ,Jfrocu..a by muscres. Also, ror rhc dog o"".n"*ting as rimitcd area for rhrough sweat. Any orher hear Ioss valid points.
3
Negadve feedback: core temperature incrcases, evaporadon and a.erioie shunt opens ,o heat is lost by radiation and conducdon ,na
srveaL.
,r;u;;;-,Jf ,ffffi?'J"li.'.T:.r';..rr*",
core remperarure down,
;;;;:,.,,
"o..
,..,i
;_ffi * :::::':::::H:T::,
closcs so less blood flows near *rc surfacc of thc skin rcducing hcat ross by radiation conduclion, core temperatura and ,ira, ro*u.d,
Posirive fcedback: core
wirh increase ra te
n"a_O arr,..
rer
; ";;;,J:'J;:;l"J:,iXl:'j::]]*.',
of metaboric reactions fur ther,
in crudi ng
";
metaboric reacrions speed up
;;::T;:"Ti: ;I:l:il,:r.. ""
5.'. i:!:r .':: !i5 _:.1.:l
".i.l t!ij :.4:i:;3.j{r'i
:
a:.:.;-:.a4
Pages 168-169
The ansrvers should include some or all of rhe following. Other poins may be
1 tS+Cl valid.
Fig. 7.4.1 shows dara lrom rhe National Statistics site collected as part of a Health Survey lor England.The samplc size is very large (ovcr i4 000 adults in 2003) so the evidence is rcl iablc.
The obcsiry data for frg.].4.2 came from a study by the International ObesityThskForce in 2002, and rhe cycling dara from drc Departrnent forTransport in 1996.These graphs summarisc large-scale intcrnarional and nauonai srudics, and are considered convincing evrdcnce.
The pie charr in fig.7.4.3 is bascd on data of ail newly diagnosed cases of diabetes in the US, and again is a large sample sizc.
'
The graph in fig 7.4.3 comcs from Narional Institute of Aging in the US, with a sample size of abour 1000 people, all ofrvhom rvcre overweight and had slightly raised blood glucose leveis, both ofwhich are good predictors for the development ofType 2 diaberes. 45% of rhe sample came lrom parricular minoiiry groups known to have a higher risk of developing d.iabetes.Thc survey compared this group rvho increased their level oi activiry rvith orhers rvho eirher receive d drug ucarncnts or placcbos. Sample size is relatively small here, bccause of thc breakdown by agc, and the cffcct of ethnic origin might mean that thcsc rcsults arcn't as valid for othcr cthnic groups.
2 tS+Cl
The answcrs shoultl include soms or all ol thc following. Other points may bc valid.
Correlation is when facrors vary in a similar way, either direcdy (going up and down at the same time) or indirectly (one going up as thc othcr gocs dorvn and vice versa).This suggcsts a link benveen the factors, e.g. something else might be affecting the factors in thc same way. Causation is rvhen a change in one factor leads to a change in another factor. A vulid mcciranism is ncedcd to cxplain thc causal link between thcm.
Much of the evidcncc for a rciarionship bet*'een level of exercise, obesiry diabetes and heart diseasc is in dre form ofcorrclation, as shorvn by the figures on rhese pages. Incrcasingly drough, scicntihc rcscarch is producing cvidcncc of causal links, c.g. that moderare exercise sucngthens the heart and circulatory system, so reducing the risk of heart disease. A causal link wirh obesity is more
difficult to shorv because many sudies BML
ignore the impact of fitness rvhich may be grcater than simple
pages 170-171
1a
8000moderaresrvimmers:largesample;
inspiteofopenagerange)sizeofsample
increases validiry and reliability.
231I,35-37 year old marathon runncrs: big sample and clear{y defined
age rangc
incrcascs validity and rcliability. 750, 40-8 1 runners: rcladvely large sample with defined,
b
if large, age range.
Thc answers shouid include some or all of the following. Other points may be valid. 10 men
running for three wecks: tiny sampie, all one gender, vcry short time scalc.
16,60-72 ycar olds modcrate excrcisc: small sample, gcnder not dcFned.
lirlexcel A2 lliology lrnplemotation and Assessmeot Guidc for-lcrchers
andTcclnicius OPcarsorr llducation Limitcd 2009
,
$
" l::*dies seem ro confirm thc hypothcsis thar r immune system shown cxcrcise benefits th by rcducing the incidc:,cc ::::T olURTIs' ls' to suggcst strongly, tt-;; sudies .Light ;;r..J seem stronslv. and nnrr onc nn. lcss l^.." srro'gly, ..,-..- , , ur;;;;;#"t exercise is damaging immune svstem as to the measurerl .; i"-";'^'^i:::::::*: o,r.:", rhe answers,;J.Til.:::T rur1rtr ur :l,Y,t|l'.i,.( arl
oI the.foilowing. other points may be
'alid.
In order to show causation, there needs to be eith many large-scale and
ovcrwhclming
ei'idence from reliable studies o. il;J: to be a clear causal from scientific research. [n-k cstablishcd currentJy neirher of thes]s
suggest that one day a causai rin-k is rvorth
,"o*"*trlrlu'"able,
although the data
pages 172-123
1
P wave: clccuical impulses favellino
frn_
e
^
_^r,
n:*H*::iltr,...,*;i:"ii:J:1";::T:ilff valve opcns
T
valve closes' vcntricics
,;;;;;;;,t"venricular
wave : repor aris ation
o".li*"*."0
,,rr,.".or"-il'*'""r,,"
"il:::l,T. ::::: :: : il::.
;.:iiil:it.T:::ff ::Til:,:: ALrial fibr.rarion: auia Incrcascs
; ffof ffi:,J,r;i:T.1 {,rhyrhm normei
,.,h
y,h
e rva
rrre hcarr.
bea ;;;il ffi;;::: 1':': inerfectivcrv; don't nli and emprv properly. eff ective,yr,,;;.:;;;,ili],:ilJi*":,|]ffi Vennicular fibrijlarion: vcnrricles
:",f ,ff
.,
,rr. ,,..rt'
:,,,"::.Ji;;;;,
ir. *.ir'nrr*,
togcthcr, conrracr no longer conrract erradcally and weakJy. Littre brood ,, pumped into the arteries which rapid fall in blood pressure, ore*.,,"" ",::,;,-::J':"".tt starving the brain, body Of,.n l.rdr-;; *'#.; and ,;";;;;;;;:.. normal hea.r .r,v,r,..*"i" an elecric shock from , O"ii.lill;r.mcdmes O,
:il#:T.t:ns€r
causes a
,.ri.ii.
pages
17L177
I a Il ;
o
ostcoarthritis the i
n,, u.. on'. I
membrane
The rvhole awa
y
co
cz
;;;;.lff :il}::
;:"#,il [.J'u...
m.k., mo.. fluid so the join, ;;:il,
;.i",
m p re t
a n d c u h j on s th e cnds thicken and the svnoviar s
;:ttthe joint capsule thickens
u.."-. #;]::::'l:": :T . o ;'."il'" :':: r','.o"l:rr. ill"J "
""" er,
o,.,, o n
"
.,.
u,,s"'
roo.
*;;,,
" to rvear awav as we', "l:::*.,,,s'[a*s
ffij:*: ...!:sur #:'T.;t#il:' " ;:lT;"il".":H ' ,,!r or ar ol the fcllowing. otlrer points valid. may , _-_
be
In People over 40, osteoartlu
'r qoual} urc result resull of vears years ofrvear joints of rvear and tear rornrs and possibly possibtv rt,..n rear on t1-,e rle rt . Ltit^i.l-::::ll' .t Being ovcnYcight "'/qrrlo'l "sttrg "nn., ovcn'cight iincreases of osteoarrhritis develooing ofosteoarrhritis ,h.;;;.. develonino a, ,,]n:r.aaras ::T::i:ies. the stain on tne ":i joirrts. People the JorJrts. occasionally occasionallv srrrrp. r-^* osreorrri,.ir;"--1"-::..:::"t suffer from unc:r 40 ^-*" knee either ei ther rhe rhis is armosr arways the,;J; resurt ;; of a generi. .""T,?, ::::y:11,"' consequence ofa Lissue, or as a delayed tea, injurv in
lt
*,:
;;;; .""0u,""',ir,;;irt:j::1".: *.', ;;;,;;,;;, thc kne. \y/h-- ^^_-:r ,rcclivc ,il::H;I:,1lfi surgicats ir is then ilt:?,Jt*""::"Y:i$il:::il"r.*.:T:;l1t:j erfe.,j". .;;i;; ;;; ;:ilil:..,::i.:.ffi:i::fil. a less
Edercel .^2 Bioroey rmpremenlation
H
dd Assessm€nr
'a'qJ nrt) ul.
Cuide for Teichers rnd Tcc hnicisns QPcarson Educrdon Limired 2o09
e
ii.!t
rl:r:I
i':1
2 a
The answer should inciude some or all of rhe follorving. Other points may be valid. Case
history
Z
Case
knee twisted foltowing tackle
much swelling around knee
joint
history 3
knee collapsed, no contact knee swollen
joint tender
joint painiui
sensation of something catching when knee
movement very painful
straightened medial meniscus tear
compleie rupture of anterior cruciate ligament (AcL)
Keyholc surgery: tlrrough a dny incision using fibre-opric tube with camera and miniaturiscd instrunrcntsl thc drmagcd are'r is cut away so healing can occur; playcr should be playing again wirhin days; no necd for radical surgery.
ACL: also uscs keyhole surgery; uscs graft of ligamcnts from patient or donorl needs two rvceks rest to allow swelling to rcducc enough to do surgery th.tr 9 months recupcration and physio*rerapy.
"ttd
In eidrer casc, an artificial knec would not providc thc same suength and flexibi.lity. This ueatment is exccllent for patients rvith pain lrom osteoartluitis because they can withstand some strain) c.g. that of moderate exercise. Top class athletes can't use them. Thcy also have a finitc uscful time, whercas a wcll-repaired knee will last a lifetime" Any other valid points.
[S+C] Thc
answer should include some qr'all
olthe follorving, Ot]rer points may
be
valld.
The IAAF's ruling in 2007 banned the use of any devicc incorporating springs, wheels or any other element that providcs rhe uscr with an advantage over another athlere not using such a dcvicc.Thc ruling against Pistorius taking parr in rhc 2008 Olympics rvas bccause tests showed athlctes using the blades used lcss cnergy than ath.leres with legs to achieve the samc speeds. Some issues; Should prosthcscs be considcred.just from what they can do biomechanically? Just because the prosthetic blades save energy, doesnlt necessarily mean that the rest of the body is saving energy, because it isn't rvorking in exactly the same way as someone
with complcte legs, for cxamplc otl]er areas ol thc body may have to work
harder to balancc.
If pcople using prosfictic limbs could all run tastcr tharlablc-bodicd athlctes, whcrc
does
that lcavc olyinpic compcdtion?
If someone using prostheric limbs is able to compere on an equaFbasis with able-bodied runners, would that relcgate the paralympics to a sccond-rate level of sport, particularly for those who couldn'r afford rhe prosrhcses?
Edexcel
42
Biology lmplemeotation and Asssstocm Guide forTiachers andTcchnicians ePcarson Educarioo Limired 2009
Pages 178_181
I
Some,d-rugs, cah create
chinge in the body, eithcr increasing.physical
].11n11.q_
3.i1T'*','*:i:T::'lf.T;:""1'.f are the ones
2 a [S+C] valid.
fiat
are
;anned onty during
:il.:,|,*.on.,,h,,.,"b.n,i.'d.*pr.,.ry excreted from the
bodv. These
""-o.oJ:::ttlv The answer should include some or all t of the iollowing. Orher l
Genes that code for natural transcription factor an advantage in sport, and at competido. l.u"r
winning
methods
.
.ro .",-i"-,"* like rhis tc .
first. Thc pie ssure
l'such
as
points may be
crydrropoiedn, can give rhe difference between
.vrn rs so grcar ," ,,:,"j1::1" rhar using,narural,
verv tempring.
b steroid hormoncs: il:ffi;:::ffiffir.
i:{"::i"l"J:*x*l ":j:...,. ffi rjil;i:l T":i=d;;'"i?,Ti,;;i.,'. il:*'.i;ilt;;ffi 3i*:*1i1::;ff : j"T:1:ruT*:;'";:ffi produced. or qDiagral rikc fi g.
:;
7.4. r
8,",,"i*, ol"?:,,J.ril?il,*bcrs
enzymes
Pcptide hormones: do not enter the cell; bind ro LU a receptor in the ccll mcmbrane; the membrane-bound complex ,.,t*,", .'r*"& thc cell cvtoplasm and niggers a prorein kinase cascade rvhich involvcs',cr.si:1:::11 acttvadon of scveral proteins until the different final product enrers dre nu.,"utt unu acts as a rranscripdon switching or, ,r,. g.rr., factor, linked to the synthesis orl protein (enzyme). (Diagram r*e
nglz.a,zo in srudcnt
3a b
d;,,;;;r:il*icular
Possible answers include: the number of students was laken from (e.g. all cities, rural areas,0,rr..., sur vey; wh o run d e d rhe s ur vey ; did It is inaccurate becar
".
the areas rvhere dre survey
;;;"; J:llT l?;Jll li,T :i.::.,"ff
t,;:ff;l'ltrffi::,ffil?
use, how drug usc the sampres.were raken.crc (as givcn ,,,
"tutt"d; irit
reflects rcgular use, on..-o',ry t, doesn't indicate where
.rrr*".,o,jot ;:1. "t
pages 182-.183
I
The error bar on the left of the graph indicates a ranse of hFr.,, time (ge *i n g,ro*.r1 uni . The measured improvemenr
d..;;
t
;;;il;
;;lf il:r,:ff :ffi :,:[:"ffi'J
in performance i";_;;;,bur rhar is similar to range' so living high and baining ro* r.,u,irJ-ut. ri,,t. difrerence rhe error ro periormance. T'hc answcrs should inclu
*rr
ffi:,
Orugs
for proving pcrformancc ll:,Lr.:,"", max-rmum red cell counr is not adequate
,,
should be allowed in sporr and
,F.elativist: setring a maximum tevel for total recl
Lt:
rr.:
is
t.mptea to add to rhcir narurar """0;;:*',:::^ .::l.t:"",
louoir damage rheir bodles using either
is. rhe
,
fotTerihcrs
and
.
" way to onry fair
hish_.rri;;.;ffiT::rilrffiwhere
Edexccl A2 Biology tmplemenmtion and Asscssminr Guidc
so
i, ,U"rvr]".,se of drugs.
they might
Gchnicianr opcarson Educarion Limircd 2009
Pages 1BB-'l89
,.'1
''''
'.lrd leavcs move torvards itl roots Ligl1r' nccdcd fgr photosynthcsis; important tlut shoots sure they grow in the right makc light hclps n".d io be in the soil so rcsponsc away from c:i-posure' of and length intcnsity dir.egdon, direction; respond ro or arvay from the pull of graviry; roots 0.rl:tty, grorfih movements of plant parts towards
g-*
helps to orientare the young plant as the seed shoots grow up, roots dorvn, rvhichever way up rhe seed is
ro*rra, $tu,ity.-s\rgp1s-qw4y;this
germinates below ground
-
-l^^, ^l pLdrrrru.
Chcmicals: p1ant. roots
will grorv towartls somc chcmicals and away from orhers'
growth' Water: roots grow towards rvuter in the soil; w'atcr nccdcd for
&nLgr'qr..someplantsorpartsofplanrsrcspondtochangesintemperaturelthere n,ryUarposirivcmovcmcnttowardslowcrlcmperaturc'e'g'manyrools'orparrsofthe planrmayrespondtoprotectthecellsandtissues,e'g.Ihododendronleavescurlinthe protect plant trssues coid; important ro help roots grorv in rhe right direcrion, and also 1o from damage in cxtrcmc cold' rcsponsc to touch' Touch, rhigmouoplsm: plants (particulariy climbing plants) grow in c.g. runncr bcans curving up cancs'
direction z'Plants respond ro srimuli by growth.They nccd to respond to sdmuli, such as respond grow. Animals to co'linug ,nd int.nsity of light, tluoughout tif. ,o that rhey can rcsponsc io nerves to stimuli oftcn by movcnrcnt,largcly through lnusclc conuactions, in stoppcd' has grorvth so they can conLinue !o respou
/? ts+cl
The ansrver should includc some or all of rhc following. other poinri may be
valid Effect of far red light (dark, buitd-up of P*)
affected
Effect of red ti8ht (tight, build-up of
seed
stimulates germination
inhibits germination
Stem
elongation inhibited by red light
elongation i5 stlmulated by far red tight exposure to far ted llght gives the ssme
Part of plant
Prq)
effect as etiolation expansion is stimutated by red tight
expansion is inhibited by far red light
chlorophytt formation stimulated
chlorophylt formation inhibited
lateral roots
growth of laterat roots is inhibited
growth of laterat roots is stimulated
flowering
in SDP5 red tight inhibits flowering in LDPs red light stimulates fiowering
in SDPs far red light promotes flowering in LDPS far rBd light inhibitr flowering
leaf
Edcsccl A2 Uiology loplcmcnrarion md Asscssmenr
cuidc forTcachcrs anriTcchniciins @Pci.son Eduouon Limiled 2009
rc
rqrnr r,1'he answers ,'t tr+Ul should ,__-s include
some or ail all oI 'rlruqc surlc of rhe the follorving. fc other points may
valid.
be
messase is produbed in leaf exposed ro periods of light and l49ds-te m.
iliT"rfi.f il;:,:._", the flowering.gpi-cgl
.
If it is a chemical ,rto r1om 1.
",",
* {',Ti:
chemical to bc made
'
arirJ
;:
-
H,H ::.l,,nffi :i,.;l ;,n:,#.";:Tj,
movcd.
Suggcsrs chemical messroo m^,,^. r-^_ , message moves from onc - plant to anolher ro stimulate florvering in
both,
il,1'ffi:::n.uj",:fi:ll!; t
"'n'
and dark
'IrrovLs
Light detectecl by phy,tochrorncs in lcavcs
pl.ntr.
short-day
+
r c e,,s
e
ar
c
light-
-
;
ofappropriate length
rccl convcrsion or Pp ro pps phy,;.;;;;;; #"::::":jllt* or ll"1."tht+. eil s * 0 j,Trff,l':, 1 ",u." ".":,il':: J:,: :;: ; J,-,tr.r,"r_,.",1",; " "i no, ie.n " i
pages 194-195
1
Photopcriodism: involvcs a major physiological chan flowering, which involves the transfer of a message from rhe reaves ro o"r".lllilh.as no*t"n.t regions of the plant; been set up, it continuJs, once ir has ::.,::^:l-" depends' 9q p-!Yla!l1r9acp- and'florigcg' Phototropisms: ,.,.,r.n ore localiscd; rely on auxinsl can easily be reversed source
*.
d";;^"
moves.
j
-'
rvhen light
Because cocoa buttcr is a fat, only fat_soluble substanlces are able to pass message passes tfuough tlLrough it.The agar (which is water-based) f,ut cannot pcnetate mcssagc must bc the fat, so the
watcr-solublc.
, ,t1", The answer should ,-.q .*ruuq include surne some or a| all of the follorving. valid. Ir E
t
In all rhe experiments shown, the depencicnt variablc
;::,li:' ffi: l, ?:il:'o
r'om
-
convcrsion of Ppa ro pp n o r'i o, g.,, i n
;J"^",:l"j:]:::*.:: ]T j or,r,".nr.*., &; il:,L:::, [ ,]' ill ]lT l' :; ;;:ffi",_..,a;; * period
"r
I ong day: dark baiance .r r
risslics orhosr prant
rhcn s plit rlic llow chart lor long-day and
Shorr day: dark period ofappropriate length or far red balance ea
i'ro
The answer should incrude some or at of rhe iolrorving. orJrer poinrs may be
:il:'
,
(,ur
sho or
ilil;;
**
"'
r'
r'.
",,i i p
Ottrer poiits may be
,
oiililjil[
ti p in to ;15'r1[::'j j;L, j]""'
a
i]l'.'ffni"Ji..,, . gar; D : substance dirrused
"
Delicate shoots so can eas ot damaged; simple design makcs invesdgations capable of being repeat.otu{ very clear; many dmes very cheaply and .asiry.
Ed*ccl42 liology tnplemenurion od
Asscssmcnr Cujdc forTilaclrcrs irndTLr :luicisns Ol>carson Educarion Limitcd 2009
{$,f''iiti;r.l: 'I
!:'r
l.ffiiiii .; a:
i;
'r,r'rli:-ti:ii-',.
pages 196-197
1 [S+CI
Unilateral light scems to causc the lAA molecules to move laterally across the light contains less IAA than the side which
shoot, so that the side of a shoot exposcd to
that the shoot tip acts as a photoreceptor. More hormone of ccli clong'.rdon on the dark side.The IAA molecules bind to spccific rcccptor sitcs on thc ccll surfacc mcmbranes, acrivadng the acdve pumping of hydrogen ions into thc cytoplasm,This changes ihe hydrogen ion conccnuation,
is not
illuminated.This
me ans
ditTuses dorvn to the region
proviciing rhe optimum pFI for the cnzymcs tl'rat brcak bonds between adjacent ccliulose microfibrils and keep thc wall flexible.The cslls absorb watcrby osmosis and the very llexibic ccll rvalls strctch and allow tl-rc cclls t
IAA on thc dark side, tircrc is more cell elongation and so
grow,th on the dark side, resulring in the shoot bending tot'ards thc light. Once the shoot is growing riirccdy towards rhc ligl-rt, rhc unilatcral srimulus is re movcd. The asymmeuic
transport ol IAA encis and thc shoot grou's suaight lowards *re light.
2
The answers should inciude somc or all of the follorving. other points may be valid.
a
went's bioassay showed that the amount of gro*th (bending when the block was placed asymmeuically) was direcdy related to thc amount of chcmical in the block. This makcs it possible to s'ay that growth torv'lrds unilatcral light must be due to higher levels of the chemical on the shaded sice rhan on rhe light side of the shoot.
b
The current model of photouopisms cxplains the differcnce in elongarion of the cells on rhc shady and light sidcs in tcrms of thc movcment of auxin from thc light to the shady side, where auxin allows rhe ccll walls to rcmain flcxible for longcr.
Iidcxccl A2 Biology Inplcmcnradon ond Asrcssmcnt Guidc forTcachcrs andTcchiciaro OPeanon Education Limhcd 2009
ffi_
198-201 Pages 198-201
1
Nervc fibre: axon of an individual (moror) the brain but nor borh.
ne
rvc ccil; may carry impulscs to (scnsory) or from
Nerve: bundle of nerve fibrcs, may bc alr scnsory, all motor or a combination of both.
2 [s+c] v.rlid.
The answer should incrude somc or a[ of thc roliowinc. other points may bc
Ncrve ccll in cNS with dcndrircs ro synapsc rvirh and rcceive inpur fiom odrer nerve cells, long axon/fibre to reach dssues, myelinared ro give rapid spced of impulse uansmission, synapses on effector to pass on impulsc.
3
In invertebrates, the speed of transmission of a nerve impurse is direcdy rerated ro diamerer of nerve flbre, and fiere is a limit to how big a nervc fibrc can grow Mosr vertebrate neurones are associatcd with Schrvann celld and thercforc hav-e a myelin sheath As a result of the nodes of Ranvier, tle uansmission of a nervc impurse is much rasrer. so vertebrate nerves thar need to carry impurses fast are myerinared, with relativery smalr diameters.Those that are not myerinarcd don't neerl lo carry impurscs very rast so they can sdll havc small diamclcrs.
4
Squid giant axons are large as they carry impulses relarively quickly during an escape response.This means that they are easy ro find and. access and easy to insert micropipenls into. squids are invertebrales, so thcrc arc arso f*vcr cthicar issues with using.them in experiments of rhis type.
pages 202-205
1
The resting potential of a ncurone is produced by the differentiar exchange of ions across rhe cell membrane.The membrane is rclarively impcrmeabre to sodium ions, but quite freely permeable to potassium ions. Thcre are arso very acdve sodium/potassium pumps which use ATP to move sodium ions our of rhe axon and potassium ions in- This lowers *re conccntradon of sodium ions inside the axon, because they are pumped_ out and cannot diffuse back in again. potassium ions are moved in to th. ..u by rhe'pumps but
they then diffuse out again arong a concentration giadient rfuough op.n .channels. Eventualry the rnovemcnr of posiriveiy charged potassium
potrsrio- ion
ions out of the celr along the concentration gradient is opposed by the elecrochemicar gradient. As a resurr, the insidc of thc cc[ is srightly negative rerarive ro the oursidc. This gives a potential difference across the membrane of around _70 mV.
Edcxcel
42 Biology Irnplcmcnution ud
Assessmenr Guide
forTerchers andTechnicians @pqrson Education Limircd 2009
:
\::_
li. r:;i:;
;:{iiii:ii:iii;iill# ,., ,..*"*,;""^,tJ:iJ;*.'i,i;".;ii*.;;J;*#*;;,;**=.*';i;*;l;*,i;".;rr*;*;l*r* 2 a
An action potcntial is dre rcsult of a suddcn and dramatic incrcase in axon membrane permcability to sodiurn ions. Spicific sodium channels or sodiuin gates open up,
'
allorving sodium ions to diffuse rapidly into thc cell.'l'hc potential difference across thc mcmbrane is briclly rcvcrscd, rvith the ccll bccoming positivc on the inside with respcct. to the outside, at about +40 mV.'Ihis depolarisation lasts about 1 millisecond.
The sodium channels thcn close again and cxccss sodium ions are rapidly pumped out by the sodium pump, using ATP ro supply cncrgy.ll:e permeability of thc membrane to potassium ions is tcmporarily increased as voltage-dependent potassium ion channels open. Potassium ions diflusc out of the axon down their concentralion gradicnt and an elccuochemical gradicnt, aLuactcd by rhe negarive chargc on thc outside of the membrare.The inside of the cell becomcs ncgative relarive ro the outside once again, and the axon is
re
It
takcs a lcw miliiscconds bcforc rhc resting potential is resrored
ady ro carry anorhcr impulse.
Thc rcfructory pcriod is thc rccovcry timc afrcr an acuon potential during which an axon membrane cannot be resrimulated. It is the time taken for the sodium pump and othcr ionic movements to restore the balance of positive and negarive ions thar produce the resting porendai. Absolute rcfractory period is when the sodium channels arc compictcly blockcd and no rcsting potcntial. As rccovcry progresses there is the rclative refractory pcriod. Its importance is that it limits thc rate at which impulses ravel along a ncrve fibrc, prcvcnting constant sucam ofimpulses, and preventing the acrion potcnrial from r-ravclling backrvards along thc fibrc.
b
An action potcntial cun bc rccordcd accuratcly by inscrting a very fine glass microclecuode into an axon, Another electrode records the electrical potential from thc outsidc. Thc results arc shorvn on an oscilloscope.
3
The graph shows that DNP prevents the pumping of sodium ions out of the axon.This suggests that the ATP is being used to powcr the sodium pump - when it runs out, the pump no Ionger works. As thc DNP is washcrl arvay rirc pumping of sodium ions out begins again, suggesring that ATP production has started again.
4 [S+C] Theanswcrsirouldincludcsonlcorall olthciolloiving.Othcrpointsmaybe valid.
The rccording from thc wholc nervc shows an increasing lcvel ofresponse to an incrcasing stimulus.This is bccausc morc and morc ncrvc cells within the nerve are responding to dre stimuius.The responsc liom the single axon shows the typical all-ornodring response pages
1
-
whcrc the responsc is thc same to
u
stimulus beyond a threshold levcl,
206-209
The movcment ola ncrve impulsc along the fibre is the rcsult of local ion movements borh in front of ancl behind the action potential. In an unmyelinaild o.ru. fibre rhese events occur all along the membrane. Although each event takes only milliseconds, dte time adds up as thc action potcnrial.uavcls along rhe fibrc.
'
In myelinatcd ncuroncs) ions can only pass in and out of the axon at the nocies of Ilanvicr,. So an action potcntial will junrp lionr onc nodc to dtc ncxt,This spccds up transmission as thc ionic movements occur much lcss frequendy taking less dnie.
Ederccl A2 Biology lmplemcnurion and Asscsm.nl Guidc forTc.chcrs andilcchniciens OPcrson Educarion Limited 2009
2 'fhey
are involved in making the neuroransmirrer subsrances in rhe presynapdc knobs; involved in the producrion of vesicles; involved in the breakdorvn of neurotransmitters in the synaptic clert; invo'lvcd in thc production of ATp !o powcr rhc various ion pumps and synthesis and breakdown of neuroransmitters. Any othcr valid points,
3 [s+c]
Theanswershouldincrudesomcorall
orthefoilorving.orhcrpointsmaybe
valid.
. Elecfon micrographs:
show rhe presence ofvesicles in the synaptic knob ofthe prcsynaptic neurone bcfore an action porcntial; aftcr rcpcatcd action potendals these vesicles are no longer visible, implying that they have released thei. co.,tents as a resurt of stimulation' Also shows largc numbers or mitobhondria that suppry the energy for the syn*resis of the neurouansmitrers cic.
Borulinus toxin: blocks the release of aceryrchoLine and so shorvs rhar acetylcholine from the presynaptic mcmbrane is needcd for thc transmission of an lcrion potential across a synap se.
Nicotine: sdmurares rhe nervous systcm by binding ro thc posr-synrptic mcmbranc, mimicking the effecr of aceryrcholine and so suggcsting that
acerylcrroline does the same.
Suychnine crc.: show thar acerylcholine causes the setting up of acrion potenrials in postsynaptic neurones, because preventing the breakdorvn of acctylcholinc causes the neurones to respond continuously.
curare: shows that blocking of acctylcholinc srops .,ansmission of acrion potenriars from nerve cells to muscle ceils confirming that acerylcholinc needs ro bir.rd to acerylcholine receptors to initiate post_synaptic porential. pages
Zi0-21''l
I
Accommodation occws whcn aLl of thc synaptic vcsiclcs in a synapdc knob are discharged as a resuit ortoo many acdon potenrials in rapid succession.Therare of synthesis ofnew vesicres cannot keep up and the neurone can no longer respond to the stimulus, A short rest restores the response as new vcsicles arc madc. Accommodation allows organisms to ignore repeated harmless srimuli so rhat the cNS does nol become overwhelrned with input.
2
spatial and temporal summadon make an orga;rism more responsive to smail stimuri rvhich might not on their own trigger a response. A response coming into several sensory reccptors at once, for example, can bc addcd togethcr to give arvareness, eg. the rods of the eye. similarly, if a small srimulus rvhich,,vould nor rigger a post-syn;pdc acrion potential on its orvn is repcatcd scvcrol timcs in quick succcssion, an organism becomes arvare of it, thus increasing scnsitivity and responsivcncss,
pages Z1Z-213
1 a '
!flhen a receptor cerl receives a stimulus, sodium ions move rapidiy across rhe cell membrere sening up a gcnerator potcnrialA small stirruius re sults in a small generator poteir:;a! and a lrrgc stimulus rcsulL: i. a largc gcncrator porendal. ir rhe
generator potenrial is large enough to reach the threshord ofthc rcceptor neurone, an action potential will result in Ihat neurone. Ifit is nor, rhere rvill be no acdon potential. Edescel A2 Eiology lmplementrtion and Assessmcnt
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cnd
rechnicians opcarson Educarion Limikd 2009
b
ln convergence, even ifthe gencrator potential liom an individual receptor cell is too small to set up an action potential, the gencrator potcntials from several may add together or summale and uigger an action potential.This makes it possible for the sensory system to rcspond to lorv-level stimuli.
2
ofthe following.Othcrpointsmaybe
[S+C] Theanswershouldincludesomcorall valid.
.
Accommodation: ovcrstimulation of any prcsynaplic ncuronc releases so many synapdc vesicles that further action potentials in the neurone can't release neuroLransmitter molecuies into the synaptic clcft and no action porendal is gcnerated in the postsynaptic ncuronc.This mukcs it possihlc for thc auirnal to conccnl.ratc on ncw) and potcntially motc important, stimuli. Rcsponse lcturns as new neuroLransmittcr is synthesised,
.
Adaptation: constant srimulation of rcccptor cclls rcsults in a gradual decline in response. Again this makes it possible for the animal to concent-rate on newi and potemially more important, sdmuii. Animal rvill not respond again rcgardless of amounts of ncurouansmittcr.
pages?14-217
I
1 a
Rhodopsin is lorrncd lrom opsin and rctinal. In the dark, rctinal is all in the cis form. Light converts this to Eans-retinal.This changcs the shape of the retinal, and the rhodopsin breaks up into opsin and rctinal.
b
The break-up of rhodopsin uiggcrs a cascade reaction that results in the closing of the sodium channels in rhe rod membrane, As the sodium pu:np continues to pump Na* out of the cell, thc inrerior bccomes more negadve than usual.This produces a generator potendal in the rod. Ifthe generator potential is iarge enough to reachthe threshold, or if several rods are stimulal€d at oncc, neurouansminer substances are rclcased into the syn';psc rvith thc bipolar ccll.This scts up an aclion potential in the bipoiar cell rvhich passcs rlcross the synapsc to cause an acdon potential in the sensory neuronc lcading to thc brain. In thc visual areas of the brainthis visual iniormation is convcrtcd into an awarcncss of thc imlgc.
2 a
Sevcral rods synapsc rvith a single bipolar cell, so summation of generator potendals is possiblc. In low light lcvcls which would not result in an action potential in the bipolar
iods can result it is less likely to uigger an action porcntial in dim light. In addition, iodopsin in cones needs to be hit
cell from a single rod, summation of generator potentials from several
ir
an action potential. Each conc synapses with a single bipolar cell so
with more light energy than rhodopsin in rhc rods'bclorc it rvill break down. So, again, thc rods rvill rcspond to dimmcr light,
b
Severai rods synapse (convcrge) on a single bipoiar ccll.This means that subde changes in light levcl as somcdring moves arc dctccted by
rodl although not
necessarily clcarly. Cones nced much biggcr iight diffcrcnces, and there is no convergence' so thcy arc lcss likely to respond to movement,
c
Concs respond only to bright light, and each individual conc synapscs onto a singie
bipolar cell. As a rcsult any image is usually clear and crisp.
Edexel AZ Siology Implementltion and
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Pages
1
218-219
The need ro move the whole body around in animals means fasrer responses are required
-
electrical coordination makes this more possibic, chemicar coordinarion dcpends
on 'diifusionandmovementinmassflorvsystemssuchasbloodandphroemanisospeedis limited. It usuaily invoives grorvth as the mechanism of response. It is sufficienr for prant responscs.
2 ts+cl rheanswershourdincrudcsomeorailof
rhefoilorvirrg.orherpoinrsmaybe
valid.
chemical coordination
P[ants
Anima[s
plant hormones (growth substances) control grow1h, movement, flowering
animal hormones
exampies: auxins (lAA) gibbereitins, itorigen retativety slow changes
maturity, response !o stress, blood
'
controI growth, development, sexual sugar Ievels etc. examples: adrenallne, testosterone, oestrogen, human growth hormone, ins
u
lin
relatively slow changes eLectrical coordination
nervous system composed of
conducting nerue celis controls rapid response to stimuli, e,g. reflexes, and brain allows
coordination of many nervous inputs ailowing learning, habituation etc. includes chemicaI transmission at synapses
can be very .apid, Long-term changes ln synapses oi brain related to
memory
Light lalling on dre sensory celrs ofthe redna causes impulses to travel along neurbnes in the optic nerve to the brain.Thc impulses arc detccted in a conrror centre in the midbrain'The impulses travel arong neurones to further conrrol cen..es.These synapse of thc parasymparhcLic cranial ncrvc (rhc oculo'oror) which transmits )l*.olun"nr,r lmpurses to the iris.The impurses in the ocuromotor ncrve fibres srimulate the effectors (the muscles of the iris) causing Lrre circurar muscres to confact and
the radial muscles to
;ffi *::::H:::,
or action siorenriars rrom
trr,",
:-.,,;:
::"
"" from the contol centres along sympathetic ngrves to the iris, the circular muscles relax and
the radial muscles contract and rviden the pupil. By reducing the amount of light entering rhe eye in bright condirions rhis reflex avoids damage to thc delicate rods and cones by overstimulatiig them. in dim right, the reflex causes thc pupil to open wicle so as much lighr as possibie fails on the rods to maximise wllat you can see.
Pagesz2o-221
I
'l'he ccrcbral hcmisphcrcs arc associatcd with highcr brain functions - seqing, thinking, learning and emotions for example. Folding of thc cercbral hemispheres increases the surface area of thcsc rcgions of thc brain. It is thought that greater lolding and thus grcatcr surf'rcc arca is associarcd with grcrre r intclligcncc, morc complcx emotions and the ability to lcarn morc complix skills. Humans have grealer abiliries than other primares, and morc folding.Thc volumc of tissuc is inrportan! too which is a function not jusr of folding but of surfuce area but lcss volume because 'Iickncss. So dolphins havc big rhe tissue layer is *Linncr. They are ve ry intciligenr but it is thought that their developmcnt docs not rival humans.
2 tS+Cl
The answcr should include some or all of the following. Other points may be valid.
Brain area
Function
cerebral hemispheres
vision, sight, thinking, learning, emottons
frontai lobe
emotional responses, planning, reasoning. decision-making primary motor cortex controts many movements
temporal lobe
sound recognit!on, hearing, speech, many memory functions
occipital lobe
vision, shape recognition, coiour vision, sense of perspective
cerebelium
coordinates smooth movements, maintains posture and batance
hypothatamu5
coordinates autonomic nervous 5y5tem, inctuding thermoregulation, and controls many basic drives, e.g. thirst, hunger, aBgres5ion, reProductive behaviour
medutta oblongata
Pages
1
controts reflex centres for heart rate, breathing rate, blood pressure, coughinS, sneezing,swallowing, saliva production, peristatsis
zzz-227
X-rays: pass *Lrough botiy, absorbcrl diflcrcnri'.rlly by diliirent tissues, make an image on phorographic.f,lm. Good for taking images of hard tissuc, c.g. bones, but much less useful
for producing imagcs olsolt tissucs such as thc blain. Computeriscd romography
(C'f scan): thousands of tiny bcams of X-rays passed
*rrough an arca of rhc body, c.g. hcad. Bcams attcnuatcd by fie density of the tissue . The X-rays which makc it through arc detccted and mcasurcd. A computer collates the data ro produce a cross-scctional image
ofa thin siicc tluough rhe body. Special dyes can
makc areas X-ray opaquc so they show up more clearly in the scan. Can identify major suucrures in rhe brain and dctcct problcms such as brain tumours, blecding in the brain
or swellings of thc artcrics in the brain (ancurisms). Cannot be used to show how areas of the brain are used or change during diffcrenr acdvides. Can be linked to observed changes in behaviour to indicate rhe importance of certain areas ofihe brain in particular functions, Magnctic rcsonancc imaging (MI{l scun): Uscs magncric licltls and r0di0 waves to image the sofi tissues (mainly due to amoun! of watcr in tissue), so no potendally damaging X-rays. Particularly good for imaging watcr in the body.The signals are analysed by computer and used to producc an image. Images show much finer detail than CT scans. Edcxccl A? Diology lnplcmcntation und Asscssmcnt Cuidc for'lilrchcrs rndTcchnicius OPurson Educrtion Linritcd 2009
2D scans are usually produccrl a computcr can creatc a 3D image fiom these. Can distinguish regions of the' brain. widely used to diagnosc brain injuries, strokes) rumours and inlections of the brain or the spine. Can also indicate links benvcen the srucrures in the brain and patterns ofbehaviour. Functionar magnetic resonance imaging ('MRI):monirors uprakc of oxygen in dirferent brain areas, so indicates active areas ofthe brain.
can be obscrvco ;n r.riti-a,
so makes it possibre to watch brain response while pcople carry ouqtasks. Gives an exrremery
'
sparialiy accurate image of the brain. Has to bc carried out rvirh parient,s head remaining complctcly still, which limits tasks that can bc clonc. uscd meinli ro investigate normal brain structure and function. May soon be used to diagnosc diseases such as the earlv signs ol suoke damage aod rhe onser of Aizheimers.
2 [s+c] valid.
The ansrver should inciude some or ail of rhe foilorving. orher points may be
Absolutist: Animals should not be uscd for cxperimenrs - in rhis case for learning more about horv the human brain might rvork. r\,roraily, experimendng on animals tha! causes pain or death is completely unacccplable, Relativist: It is morally more acceptable to cxpcriment on an.imals as a model lor humans rvhere there is a posirive purpose ro the rcsearch, e .g, it will benefit rhe ueatrnent
of
irumans with disease or damage to the brain. pages 22&_231
1 [s+c] Theanswcrshouldincludcsomcorrll a
b
ts+ cl 2 '
Absolutisu it is completely unacceptable to experiment on animals causing pain or death. Relarivist: the work of veisel and Ilubcl could nor ethically have been carried our on humans, but it was important research that helps us understand the development of rision in mammals, including humans. It rvould not be erhical ro use primates lor this work as it was not direcdy of mcdical benefit, but kinens are more readily available experimental animals and therefore it is acceptablc to usc thenr.
Animal rvork with embryos examining the srrucrure ol to show rhat the basic stucturc dcvelops at regardless of inpur.
' .
*,.
a specific stage
brrin
as it is.laid down offcrar development
Animar rvork with kittcns sdtching eycs srrut at various stagcs of developmcnt to show rhat there is a criticar window during which ross of sight becomes permanenr, suggesting that dris is when the mature visual cortcx devclops.
Animalrvorkwirhmonlcvsshorvingsamethingas\\.or, cntrcal pcl lod.
'
ofr]refollorving.orherpointsmaybevalid.
Absolutist: it is completely unacceptable to experiment on animals causing pain or death. Relativist: the work of crowley and Kau could not cthically havc been carried out on humans, but ir rvas important research that helps us understand the deveropment of vision in mainmals, incluaing humans and drcrcfore jusriticd uring pri,.',"r.
\viLhkinens_different
Human obscrvations, made on babies who are blind for some rcason during the critical window, e.g. babies who nceded surgery on cataracts etc.
Edcxccl A2 Biologv Implemenratioo and Assessmcnr Guide forTeachcrs aDdrcchnicirns opcarson Education Limircd 2oo9
..i:"::
.:; .t,
t:lrx
?,
il
Answcrs should show aw{rrcncss rhat it is unethical to cxperiment on human infants in thc rvay rvork has bccn donc on kittcns and monke.vs, and that evidence might come from circumstances rvhere babics are born with damage to brain areas or who are temporarily blindcd/cicprivcd of sight for sonrc rcason.
They wcre the fust people to shorv that rhe brain is very plastic; rhat at birth, although many ofthc ncural arcas arc prcscnt) thcy nccd input and cxpcricnce to develop and work fully.They dcveloped the idca and produced evidcnce to supportthe concept ofcritical rvindorvs of development rvhich underpins much of our subsequent understanding of how the brain works. gages 23?-237
1
The period ol time during rvhich vital neural connections are made in the brain in rcsponse to specific stimuli.
Nature: axons from the lighr sensidve cells in the retina grow synapsb in visual cortex in a very regular way known as ocular dominance columns. Neighbouring columns of cells receive input from the same area of the redna from the left eye and the right eye.
'
Nurturc: right srimulation nccdcd during cridJal windorv ol dcvelopment for the area of the brain to develop propcrly. If rhe nccessary input during the critical period of dcvelopmcnt
fai1s,
thc opportunity to makc thc viLal ncural conncction can be lost
permanendY.
2 [S+C]
The answer should includc some or all of the foilorving. Other poinrs may be valid.
Must consider the necds of the baby first and thc needs of research less important, c.g. ir would be erhically unacccptabic ro lcave a ncrvborn baby with cataracts in order to test a hypothesis whcn it is known that the cataracts rviil inicrlere with the development of vision as the baby grows up. As long as the baby is not harmed or deprived in any way, Ihcn research could bc acccptablc. J
JO
b20 c
Each time a crirical window of dcvclopmcnt appcars, new neurones and conncctions arc laid down
brain.
lf
if the appropriatc stimulus is prcsent.This
incrcases the size of the
the child is dcprived of the stimulus, the brain does not develcip fully, and
once the cridcal window has passed, that damage cannot be undone so lhe brain ends
up smaller. In childrcn who suffer severe neglect, many critical windows are missed and so brain dcvclopmcn! is scvcrcly alfcctcd.
4 tS+C] The answer shouid include some or all of the following.
Othcr points may be valid.
Damagcd brains: shorv rvhat happcns to thc pcrson as a rcsult ofepecific damage or disease; may be difficuit to separate the effect on specific areas of the brain if more than one rcgion damagcd;somc kinds of damage are vcry rarc, so takes a long time to collect sufficient cvidcncc ol its cffcct. Newborn babies: looks at horv newborn babies respond to different stimuli; very limited in what can be donc as cannot harm thc babies; useiui because the effect ofnurrure is minimal at this stage, so c:rsier to separate from the efici:is of nature. Erlcrccl
A!
lliology Inrplcmentation rnd Asscssmcnr Guidc for'lirclrcrs and l'ccluricians Ol'crrson l-ducction Limitcd 2009
Twin studies and face recognition: comparison olresponses from lraternal and iclentical tw'ins; should hclp to separatc our rhc cllccts of r]'c cn*ironmcnr and the genes. Howc'cr, rhis assumes thar idenrical rwins develop identically from their genes, and this may not be
uue in all cases.
.
Cross-cnltural studics: looks at thc impacr of dillcrcnt bclicls and mcthocls on behaviour; can be used to look at distinct differences in nurrurc. IJowevcr, cvery individual is different and not everyone is alfected by rheir culrure ro dre same extent.The level of these differences benveen individuals may be difficult ro.measurer and so dilficult to correlate rvith the resulls from the study.
pages 238-239
1
lnnate behaviour shows there are genetically determined responses to certain srimuli *'I.ricl: occur as a rcsuk of specilic ncrvc pathrvays laid dorvn in the embryo from the instructions of the DNA.The stimulus for a piece of innate bchaviour will always elicit the same response and thc development of thcse neural pathrvays in the brain depends almost enrirely on the informadon in the DNA.
2
Animal behaviour can be used ro see the importance of nature on brain development through the srudy of innate behaviour ancl the role it plays in animals of dillcrenr species. Lcarning behaviour lrom habiruation and condirioncd reficxcs ro exploratory and insight learning all play an important role in deveroping understanding of nurrure in brain development.'Vhich behaviours are completely the result of gcnetic pathways and which depend on learning (nurrure) as well. For example, marernal behaviour might be thought to be instincrive and some aspects arc, but animals rvhich arc hand-rcared with no conract rvi*r rheir own species are.often incompetcnr mothers. Any othcr valid points
pages
1
240-241
Invertebrates with fast irnpulses in unmyelir.rared nerves have rclarively largc diameter nerve fibres rvhich make the {lbres rclatively easy ro idcntily and sdmulare artificially. Also, as invertebrales, less ethical issues arise from their use as experimental animals,
2 [s+c]
The answer should include some or all of rhe following. orher points may be
vaIid.
Habituarion and accommodation both lead to the reducrion in rcsponse to permanent or rapidly repeated srimulus. Accommodarion is rhe physicar rcsurt of dcpretion of ncuroiransmirrer and synapric vcsiclcs in drc synapric knob ofa prcsynapdc
neurone.
After a brief absence of rhe stimulus (action porendal in
prcsl,nxptic ncuronc), the neurotransmifter and vesiclcs arc resynthcsiscd rnd rlrc rcsponsc rcsrorccl. Habituation the result of.loss of response of tl-re calcium ion channels in rhe presl.naptic membrane, resulting in a ioss ofrcsponse to an aclion polential in the ncuronc. It is a rearning r-he
is
response' and can be retained over a long time, reducing the response to things that happen constan'jy or very frequendy and so lcaving thc brain betrcr able ro focus on
occasionally changing s'-rmuri which may be more impr.:tant for survivar.
Edexcel A2 Biology
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I
Ncurotransmittcr synthcsis and storagc: If a drug blocks lhis proccss, s5'naptic trrnsnrission *'ould lcsscn ancl thcn stop rs supplics oI ncurotransmitter rcduced. This rvould mcan nerves using drat ncurotransmittcr rvould no longerbe able to pass impulscs bctwee n thcm, causing loss of motor or scnsory skills and processcs in the brain. NeuroEansmitter telcasc: A drug stopping ncurotransmittcr rclcase tvpuld st-op synapilc ransmission as the impulse in the presynapuc llbrc would notbe uansmitted to the postsynapric membrane causing ioss of motor or sensory skills and p.ocesses in the brain.
Neurotransmitter-receptor binding: A drug blocking this rvould slop lhe development of rhc posr-synaptic potcndrls rvhich in rurtr would prcvcnt tlIc development of an acdon potcntial in thc post-synaptic 6brc. Alrcrnativcly the drug may maintain binding so thar rhe stimulus to the posr-synaptic fibre was conLinuous, causing confusion and farigue
lurthcr in lhe system. Ncurouansmirtcr rcuptakc: a cirug blocking this rvouid slorvly rcducc
tl-rc
iutcnsity of tirc
rcsponse as less neurotransmiticr rvould bc resynthcsiscd and be ready for rclease.This rvotrlri slrccd rtp fnrillrtc ctc. a drug blocking *ris rvould mean that sdmularion would continue as the concenlr4tion of neurotransmitLer in tJrc synaptic gap rvould build up steadily so therc rvould be consLant stimulaLion of tl-rc post-synapLic mcmbrane and
Neuroransmittcr brcakdown:
latiguc.
Z
Dopaminc synapscs: produce tltc neurolransmitter dopanrine, the axons from them spread tlrough the fronral corrcx, rhc brain stcrn and thc spinal cord, so thcy are closcly involved in the conuol and coordinarion of movcment. Scrotorlilt synupscs: pLorluec scr'otolrin in t groLrp of cclls in rl:c brain sicm rvith axtlns that spread throughout the brain inro thc coltcx, thc cerebellum and the spinal cord.They have a rvidespread influcncc on cclls throughout thc brain so low levels mean overail brain acdviry is supprcsscd. Particularly reiatcd to diprcssion. L-dopa
EcstasY
precursor of dopamine so crosses the btood*brain
crosses blood-brain banier
barrier enables brain cetls
to maximise dopamine
production
affects serotonin synapses in brain, blocks the serotonin reuptake system so synapses flooded with serotonin, and may cause retease of alt the serotonin from presynaptic knob. ilooding br:in
with serotonin relieves stiffness and slowness of movement
acts as stimuLant to brain and ptychotropic
therapeutic
improves mood, sense of well-being, energy etc. physiological effects include increased heart rate, change in thermoregutation, loss of thirst sensation, orevention of urine production by kidney
lidcxccl
A2 llioloijy
Ln
-l il"mcntu'ioo rnrl Ai*cssmcnl Cuidc for r-;hcrs rod'icchnicirns 4)Pcrrsnn Ilducrric;.
1
.:nilcd 2009
4
[S+C] valid. sSRIs seem to work by blocking the serotonin reuptake proteins and so maintain a relatively high level ofserotonin in thc synaptic clefr, to bind wirh the post-synapdc membrane receptors. Horvever the working hypothesis from the genetic
evidence is the
opposite.The short form ofthe seroronin reuptake protein allere and its frequency (i.e. in homozygous or hetcrozygous state) afrcct rvhether or not lhc person is likely to suffer from depression. People with the short form produce less ofthc reuptake protein so serotonin is taken up more slowly by the presinapric neurone aficr its rerease into the synapse. Logically this rvould rcsult in riore scroronin bcing left in rhe synapric clefr anci sc less depression - in the same wa]- as oeopre respond ro SSRIs. ln realiw, peopre rvirh dte short form are more likely to expcriercc c.lcprcssion. Pcrhaps rhcy have lcss scroronin available in the presynapdc knob to be rclcascd rvirh *rc subscqucnr impulses? Furri:rer investigarions rvould need to look at horv much serotonin is in the prcsynapric knob, and/ or horv much and how Iong seroronin remains in rhe synapric clc[r in rhe diffcrent generic iorms and during trcatment with SSRIs. pages Z4B-25'l
1
The Human Genome project has idenrified alr or the human gcnes and incrcasingly identifies the genes thar are associated rvith particular diseases and risk g.o'pr.Tii, i, th" information on which pharmacogcnomics builds as ii dcvclops medicincs *rat ivork wirh
a pardcular genome,
2
The abiliry to prescribe fic right drug for an individual padenr rhrr rvould work with their parricular genetic makeup. It wourd increase the abiliry to prcscribc the right and rowest possible dosage with minimal risk ofside effccts or adverse drug reacdons.
3
[s + c] The ansrver should incrudc somc or all of thc folrorving. orhcr poinrs may be valid.
Itlentificadon of genes for trcarment: Lime-consuming and expcnsivc; rcsponse to drugs can be complex; should the moncy be invcsred in this kind of rcscarch that will benefit just groups of people, or wourd it be betrcr to spcnd it on somcdring ,h", b.;;;;cvcryonc?
cost: having idcntified rhat only
l proportion of a popuration u,il bcncfit, is it socialry and morally acceptable to produce a drug that works for thcm, br,rt not one that *,orks lor r others in that population) Knorving your genes: shourd only you knorv, or should genomes be stored for anarvsis by drug companies ro herp rhcm dccidc whar drugs rJrcy shouid lbcus on? should individuals bc told about gene vrriants rh'.rt mry lead to other problems *rat can,t be tackled, or is it bctter nor to know? Cost of training: to keep doctors and pharmacists up to date; rvill cost sociefy but would
be essential.
Edercet A2 Biotogy lmplementauon and Arsessmcnr
cuidc for'lccchcrs anJ'lechnicirns
Gll,carson Education
Limired 200i1
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[S+C]
1'he ansrver shouid include some or all of the follorving. Other points may be
.
valid. Nlany possibilities including: kappa-opioids as painkillers lor women; screening for cytochromc P450 bcforc drug trials; idcntifying 'at risk' ir.rdividuals for certain rypes of cmcer to allorv reatment belore lhe canccr starts; P-glycoprotein transporter substance affects the ability of pcople to takc up digoxin, a hcart drug - onc gcnotypc rcsults in a far grcatcr uptake of dre drug than anotherl racial variador-rs, e.g. incidcnce of hcarr disease in Asian populadons and dcvelopment of drugs targctted at peoplc with a spccrlic genetic profile. Pages
1
252-257
The diagram given herc is a minimum. Givc crcdit for any correct extra details
gene inserted using DNA iigase
niodificd bactcrium makes drug as new gene expressed
[S+C] The
(i)
answer should include some or ail of thc following. Other points may be valid.
Wrong to use gcnclically enginccred organisms under any circumstances,
(2) Thc potcntiai bcncfits ol thc use of gcnetically cngincered microorganisms far ounveigh any risks.
3a
Drugs from GM plant
Drugs from CM microorganism
required gene cut from human or other organism and inserted into Ti plasmid of Ag rc b act e t i u m tu m ef ac i e n s
required gene cut from human or other organism and inserted into plasmid
plant cells infected by modified A. tumelaciens which transfers desired gene to the ptant
plasmid transferred into host bacterial cells v/here it becomes part cf bacterial DNA, marker
genome
gene usually added
plant cells then cloned on suitable hormonecontaining medium to produced mass of
bacteria identified by marker cultured in fermenters to make new protein drugs
undifferentiated modified plant cells piant celts then transferred to suitabie medium to produce huge numbers of CM planttets that will mature to produce the desired drug in theit
downstream processing required to separate the microorganisms and the desired end-product
leaves/[ruit etc. 42 Biology lmplementato! and Assosmenr Guidc forTecchcrs
ffi
add
Techoiciins 9Petuson Education Linitql 2009
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Risks: cost of developmcnt may crctcr companics ancr
mai'use in less-deveioped countries, possibiliry that GM crops rvill inrerbreed with rviid species and change them, or rhat Glr,l planrc rvill lose thcir abiliry to produce drc vaccine. Benefits: long-rerm, reladvery cheap, can be grown by communiries that need them around the rvorrd, no problems lvith needing cool storage or speciarised medical pcrsonnel to deliver, easy for children or adults to takc.
IS+c] -l'heanswershouldincludesomeoralrofthefoilorving.or},erpointsmaybe valid. Possible examples include : blood-clouing ftctors F:rcror
VII and IX lrom goar/sheep/ rabbit milk; alpha-1-antiuypsin from shccp milk; ATryn (for' trcrring l'rcrcditary anrithrombin dcficicncy) lrom goat milk. Evaluadon will depend on drug chosen, but should includc an assessment of cost tlf producing the drug, cflcct on animals usccJ, strcccss ol'prpgcclrrrc uscd to crcrrc ua'sgcnic animals, benelis to people rvho are rreated wirh the drug compared rvith previous feauTrcnr.
IS+c]
Theansrvershourdincrudesomeorall ofthcfoiloiving.oLherpointsmaybe
valid. Ansrver nceds to includc poi.ts such as gcncricaily vaccines, GM crops etc.
*ociirictl microorganisms, plant
Benefits inciude:
' . '
specific drugs ma
'
plants modified to suir growing condirions/nutritional rcquircmcnrs Risks inciude:
' ' '
erc.
risk of relcasc into outsidc worlLi risk of conramination of natural plants lvi*r gene markers, c.g. inferillity cost to countrics which cannot arford the GM technology for drug or foods.
Edexcel A2 Biology Implemcntatioo and Asscssmcnr Guide forTclchcrs and rcchnicians opearson Educarioo Limited 2009
