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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-zmediumzinzwhichzenzymezcatalysedzreactionsztakezplacez(metaboliczreactionsz)zandzreadilyzdissolveszsubstanceszlikezinorganiczionsz(zaszwaterziszdipolarzsoztotallyzsurroundszthezions)z,zexcretoryzproductsz(urea/ammonia)z,zrespiratoryzgaseszandzsmallzhydrophiliczmoleculesz(zaminozacidsz,zetc) 3)zWaterzhaszazhighzlatentzheatzofzvaporisationz(lotszofzenergyzrequiredztozbreakzhydrogenzbondszbetweenzwaterzmoleculeszsozazlotzofzenergyziszusedzupzwhenzwaterzevaporatesz)zsozhelpszwithztemperaturezcontrolzaszevaporationzofzsweatzcoolszhumanszdownz 4)zWaterzhaszazhighzspecificzheatzcapacityz(ztozseparatezthezmanyzhydrogenzbondszrequireszazlotzofzenergy)zsozactszaszazbufferzandzresistsztemperaturezchangesztozmaintainzazconstantzinternalzbodyztemperaturez 5)zWaterzhaszlargezcohesivezforcesz(zaszhydrogenzbondszstickztogether)zsozallowsztransportationzofzsubstances(zwaterztravellingzinzcolumnszinzxylem)zandzmeanszwaterzhaszazhighzsurfaceztensionzwhenzitzcomeszintozcontactzwithzairz(zallowingzpondzskatersztozwalkzonzitszsurface) Whyziszwaterzdipolarz?z-zCORRECTzANSWER-Aszwaterziszmadezupzofztwozhydrogenzatomszandzonezoxygenzatomz,zthezhydrogenzatomszhavezazslightlyzpositivezpolezandzthezoxygenzatomzhaszazslightlyznegativezpolezmakingzwaterzdipolar. Hydrogenzbondsz-zCORRECTzANSWER-Slightlyznegativelyzchargedzoxygenzatomziszattractedztozthezslightlyzpositivelyzchargedzhydrogenzatomzofzotherzwaterzmolecules.zThezattractionzbetweenzoppositezchargesziszcalledzhydrogenzbonding,zwhichzarezweakzbondszbutzstrongzinzlargeznumbers.zThiszmakeszwaterzazmajorzcomponentzinzcells Hydrolysisz-zCORRECTzANSWER-Breakszazbondzbetweenztwozmoleculeszbyzthezadditionzofzazmoleculezofzwater Condensationz-zCORRECTzANSWER-Joinsztwozmoleculesztogetherzwithzthezformationzofzazbondzbyzthezremovalzofzazmoleculezofzwater Polymerz-zCORRECTzANSWER-Azmoleculez(zcarbohydrate,znucleotidezorzprotein)zmadezupzofzmanyzmonomersz(zsmallzrepeatingzunits)zjoinedztogetherzbyzcondensationzreactionszandzbrokenzdownzmyzhydrolysis Monosaccharidesz-zCORRECTzANSWER-ArezthezmonomerszfromzwhichzlargerzcarbohydrateszarezmadezandzcontainzthezelementszCzHzandzO.zTheyzarezsweetzandzsolublezandztherezarezthreeztypesz:zfructosez,zglucosezandzgalactose.zHexosezsugarsz(glucose)zhavezthezformulazC6H12O6 Glucoseziszthezproductzofzphotosynthesiszandzazmajorzsubstratezofzrespirationz,zdrawztheztwozstructuralzisomerszofzglucosezinzlongzandzshortzhandzandzstatezthezdifferencezbetweenzthemz-zCORRECTzANSWER-Onzcarbonz1zinzbetazglucosezthezhydroxylzgroupz(OH)zpointszupwardszandzinzalphazglucosezthezhydroxylzgroupzpointszdownzonzcarbonz1 Sucrosez-zCORRECTzANSWER-Glucosezandzfructose Maltosez-zCORRECTzANSWER-Glucosezandzglucose Lactosez-zCORRECTzANSWER-Glucosezandzgalactose Howzdozmonosaccharideszjoinztogetherz-zCORRECTzANSWER-Byzcondensationztozformzazglycosidiczbondzbetweenztwozmonosaccharideszandzazdisaccharidezandzazmoleculezofzwaterzarezformed Disaccharidez-zCORRECTzANSWER-Twozmonosaccharideszjoinedztogetherzbyzcondensationzformingzazglycosidiczbond.zTherezarezthreeztypesz:zmaltose,zsucrosezandzlactose.zTheyzhavezthezchemicalzformulazC12H22O11 Drawzthezhydrolysiszofzmaltosezinzstructuralzformulazandzshortzhandzformulaz-zCORRECTzANSWER- Testzforzstarchz-zCORRECTzANSWER-Addziodinezsolutionztoztheztestzsamplez,zifzstarchziszpresentzcolourzchangeszfromzyellowztozazblue-blackzcolour. 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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

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