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2023 AQA A level BIOLOGY 7402/3 Paper 3 Question Paper & Mark scheme (Merged)|| Latest 2024
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2023 AQA A level BIOLOGY 7402/3 Paper 3 Question Paper & Mark scheme (Merged)|| Latest 2024 Whatzarezthezusefulzpropertieszofzwaterzandzwhyz?z-zCORRECTzANSWER-1)zWaterziszazmetabolitez-zinzmanyzmetaboliczreactionszincludingzcondensationzandzhydrolysisz 2)zWaterziszazsolventz-zmediumzinzwhichz...

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  • October 3, 2024
  • 99
  • 2024/2025
  • Exam (elaborations)
  • Questions & answers

Subjects

  • hydrogenzbondsz
  • enzymes
  • 2023 aqa a level biology 74023 paper 3 question p
  • whatzarezthezusefulzpropertieszofzwaterzandzwhyz
  • whatszthezfunctionzandzdescriptionzofzazchloropla

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  • 2023 AQA A level BIOLOGY
  • 2023 AQA A level BIOLOGY

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2023 AQA A level BIOLOGY 7402/3 Paper 3 Question
Paper & Mark scheme (Merged)|| Latest 2024


Whatzarezthezusefulzpropertieszofzwaterzandzwhyz?z-zCORRECTzANSWER-1)zWaterziszazmetabolitez-
zinzmanyzmetaboliczreactionszincludingzcondensationzandzhydrolysisz


2)zWaterziszazsolventz-
zmediumzinzwhichzenzymezcatalysedzreactionsztakezplacez(metaboliczreactionsz)zandzreadilyzdissolveszsubs

tanceszlikezinorganiczionsz(zaszwaterziszdipolarzsoztotallyzsurroundszthezions)z,zexcretoryzproductsz(urea/am
monia)z,zrespiratoryzgaseszandzsmallzhydrophiliczmoleculesz(zaminozacidsz,zetc)

3)zWaterzhaszazhighzlatentzheatzofzvaporisationz(lotszofzenergyzrequiredztozbreakzhydrogenzbondszbetwee
nzwaterzmoleculeszsozazlotzofzenergyziszusedzupzwhenzwaterzevaporatesz)zsozhelpszwithztemperaturezcontr
olzaszevaporationzofzsweatzcoolszhumanszdownz

4)zWaterzhaszazhighzspecificzheatzcapacityz(ztozseparatezthezmanyzhydrogenzbondszrequireszazlotzofzenergy
)zsozactszaszazbufferzandzresistsztemperaturezchangesztozmaintainzazconstantzinternalzbodyztemperaturez

5)zWaterzhaszlargezcohesivezforcesz(zaszhydrogenzbondszstickztogether)zsozallowsztransportationzofzsubsta
nces(zwaterztravellingzinzcolumnszinzxylem)zandzmeanszwaterzhaszazhighzsurfaceztensionzwhenzitzcomeszint
ozcontactzwithzairz(zallowingzpondzskatersztozwalkzonzitszsurface)



Whyziszwaterzdipolarz?z-zCORRECTzANSWER-
Aszwaterziszmadezupzofztwozhydrogenzatomszandzonezoxygenzatomz,zthezhydrogenzatomszhavezazslightlyzp
ositivezpolezandzthezoxygenzatomzhaszazslightlyznegativezpolezmakingzwaterzdipolar.



Hydrogenzbondsz-zCORRECTzANSWER-
Slightlyznegativelyzchargedzoxygenzatomziszattractedztozthezslightlyzpositivelyzchargedzhydrogenzatomzofzo
therzwaterzmolecules.zThezattractionzbetweenzoppositezchargesziszcalledzhydrogenzbonding,zwhichzarezwe
akzbondszbutzstrongzinzlargeznumbers.zThiszmakeszwaterzazmajorzcomponentzinzcells



Hydrolysisz-zCORRECTzANSWER-
Breakszazbondzbetweenztwozmoleculeszbyzthezadditionzofzazmoleculezofzwater



Condensationz-zCORRECTzANSWER-
Joinsztwozmoleculesztogetherzwithzthezformationzofzazbondzbyzthezremovalzofzazmoleculezofzwater

,Polymerz-zCORRECTzANSWER-
Azmoleculez(zcarbohydrate,znucleotidezorzprotein)zmadezupzofzmanyzmonomersz(zsmallzrepeatingzunits)zjo
inedztogetherzbyzcondensationzreactionszandzbrokenzdownzmyzhydrolysis



Monosaccharidesz-zCORRECTzANSWER-
ArezthezmonomerszfromzwhichzlargerzcarbohydrateszarezmadezandzcontainzthezelementszCzHzandzO.zTheyz
arezsweetzandzsolublezandztherezarezthreeztypesz:zfructosez,zglucosezandzgalactose.zHexosezsugarsz(glucos
e)zhavezthezformulazC6H12O6



Glucoseziszthezproductzofzphotosynthesiszandzazmajorzsubstratezofzrespirationz,zdrawztheztwozstructuralzis
omerszofzglucosezinzlongzandzshortzhandzandzstatezthezdifferencezbetweenzthemz-zCORRECTzANSWER-
Onzcarbonz1zinzbetazglucosezthezhydroxylzgroupz(OH)zpointszupwardszandzinzalphazglucosezthezhydroxylzgr
oupzpointszdownzonzcarbonz1



Sucrosez-zCORRECTzANSWER-Glucosezandzfructose



Maltosez-zCORRECTzANSWER-Glucosezandzglucose



Lactosez-zCORRECTzANSWER-Glucosezandzgalactose



Howzdozmonosaccharideszjoinztogetherz-zCORRECTzANSWER-
Byzcondensationztozformzazglycosidiczbondzbetweenztwozmonosaccharideszandzazdisaccharidezandzazmole
culezofzwaterzarezformed



Disaccharidez-zCORRECTzANSWER-
Twozmonosaccharideszjoinedztogetherzbyzcondensationzformingzazglycosidiczbond.zTherezarezthreeztypesz:
zmaltose,zsucrosezandzlactose.zTheyzhavezthezchemicalzformulazC12H22O11




Drawzthezhydrolysiszofzmaltosezinzstructuralzformulazandzshortzhandzformulaz-zCORRECTzANSWER-



Testzforzstarchz-zCORRECTzANSWER-
Addziodinezsolutionztoztheztestzsamplez,zifzstarchziszpresentzcolourzchangeszfromzyellowztozazblue-
blackzcolour.

,Testzforzazreducingzsugarz-zCORRECTzANSWER-
HeatzwithzBenedict'szreagentz(zblue)zandzifzreducingzsugarziszpresentzazbrickzredzprecipitatezwillzform



IssueszwithzthezBenedict'sztestz?z-zCORRECTzANSWER-1)zItzisznonzspecificz-
zdoesn'tztellzwhichzreducingzsugarziszpresentz,zazbiosensorzcanzbezusedztozdetectzforzspecificzsugarsz


2)zIt'szqualitativezsozcolourzchangeziszbeingzmeasuredzsozcan'tzobtainzconcentrationzofzreducingzsugarzbutz
allowszanzestimatezforzhowzmuchziszpresentzinzthezstrengthzofzthezcolour

3)zIszsubjective



Howztozquantifyzresultszonzthezconcentrationzofzunknownzglucosezconcentration?z-zCORRECTzANSWER-
Usezazcolorimeter,zaszazserialzdilutionzofzknownzglucosezconcentrationszcanzbezmeasuredzproducingzazsetz
ofzsolutionszwithzknownzconcentrationsz.zThezBenedict'sztestzcanzbezperformedzwithzeachzofzthesezandzth
ezcolourzintensityzmeasured.zAzCALIBRATIONzCURVEzcanzbezproducedzfromzthezresultszandzusedztozreadzif
fzthezconcentrationzofzglucosezinzanzunknownzsolution.



Testzforzaznon-reducingzsugarz?z-zCORRECTzANSWER-
HeatzthezsamplezwithzBenedict'szreagentzandzifztherezisznozcolourzchangezazreducingzsugarzisznotzpresentz
butzaznon-reducingzsugarzcouldzbe.

Heatzazfreshzsamplezwithzdilutezacidz(zwhichzwillzhydrolyseztheznonzreducingzsugarzintozitszconstituentzmo
nosaccharides).

NeutralisezwithzalkalizandzcarryzoutzthezBenedict'sztestzagainz

Ifztheztestziszpositivezforzaznon-reducingzsugarzitzwillzformzazbrickzredzprecipitate



Polysaccharidez-zCORRECTzANSWER-Threezmainztypesz-
zstarchz,zglycogenzandzcellulosezwhichzarezchainszofzmanyzmonomerszofzglucosezformedzinzcondensationzr

eactions.



Starchz-zCORRECTzANSWER-
Starchziszusedzforzenergyzstoragezinzplantszandziszmadezfromzcondensationzofzalphazglucose.

Amylose-zcompactzhelicalzchainszsozstorezlotszofzglucosezinzazsmallzspacez

Amylopectinz-
zbranchedzchainszwhichzallowzmanyzendsztozbezquicklyzhydrolysedzbyzamylasezenzymesztozreleasezglucose
z


Insolublezandzlargezsoznozosmoticzeffectsz,zinertzandzcannotzdiffusezoutzofzthezcellszwhichztheyzarezstoredzi
nz.

, Cellulosez-zCORRECTzANSWER-
Majorzcomponentzofzplantzcellzwallszmadezupzofzbetazglucosezmonomerzinzazcondensationzreaction.

Chainszofzbetazglucosezmoleculeszformzlongzstraightzunbranchedzchains.

Thesezchainszrunzparallelztozeachzotherzandzhydrogenzbondszformzcross-
linkageszbetweenzchains.zThesezmanyzhydrogenzbondszprovidezhighztensilezstrengthzwhichzmakeszthezcellz
wallzrigidzandzpreventszosmoticzlysis

Hydrogenzbondszalsozformzstrongzfibreszcalledzmicrofibrilszwhichzarezgroupedzintozfibreszwhichzprovidezst
ructuralzsupport.



Glycogenz-zCORRECTzANSWER-
Energyzstoragezmoleculezinzanimalszfoundzinzliverzcellszandzinzmuscleztissuezandziszmadezfromzthezconden
sationzofzalphazglucose.z

Compactzsozstorezlotszofzglucosezinzazsmallzspacez

Iszquicklyzhydrolysedztozreleasezsolublezglucosezaszmanyzendszforzamylasezenzymesztozattackz

Largezandzinsolublezsoznozosmoticzeffectsz,zinertzandzcannotzdiffusezoutzofzthezcellszwhichztheyzarezstoredz
inz.



Namezthez4zinorganiczionszandzstateztheirzrolez-zCORRECTzANSWER-
Inorganiczionszoccurzinzsolutionzinzthezcytoplasmzandzbodyzfluidsz(zbloodz,ztissuezfluid)z

Hydrogenzionsz-zaffectszpHzlevels,zthezhigherzthezconcentrationzofzH+zionszthezlowerzthezpH(zmorezacidz)z

Ironzionsz-
zimportantzcomponentzofzhaemoglobinzwhichzcarrieszoxygenzaroundzthezbodyzinzthezredzbloodzcellsz


Phosphatezionsz-
zcomponentzofzDNAz,zATPz,zRNAzandzphospholipidsz,zbondszbetweenzphosphatezgroupszstorezenergyzinzAT

Pz

Sodiumzionsz-zinvolvedzinzthezabsorptionzofzglucosezandzaminozacidszinzcoztransportzinzthezsmallzintestine



Aminozacidsz-zCORRECTzANSWER-
Arezthezmonomerszfromzwhichzpolypeptideszarezmade.zProteinszarezmadezupzofzonezorzmorezpolypeptide
zchains.zAllzaminozacidszcontainzthezelementszCzHzOzandzNzandzarezmadezupzofzanzaminozgroupz(NH2)z,zazc

arboxyliczacidzgroupz(COOH)zandzazvariablezgroupz(R)

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