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AQA A-LEVEL BIOLOGY PAPER 1 2021 QUESTIONS AND ANSWERS UPDATED 2024 - 25
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AQA A-LEVEL BIOLOGY PAPER 1 2021 QUESTIONS AND ANSWERS UPDATED 2024 - 25
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AQA A-LEVEL BIOLOGY PAPER 1 2021QUESTIONS AND ANSWERS UPDATED 2024 - 25
1.1,Describe,the,induced,fit,model,of,enzyme,action,and,how,an,enzyme,acts,as,a,catalyst.,,ANS,-,,-
,The,substrate,binds,to,the,active,site,and,forms,an,ES,complex.
-,The,active,site,changes,shape,slightly,so,it's,complimentary,to,the,substrate.
-,This,reduces,the,activation,energy.
1.2,Tick,one,box,to,show,which,are,the,substrate,the,scientists,must,add,to,the,reaction,mixture,is,to,pro
duce,ATP.,,ANS,-,,-,Adenosine,diphosphate.
1.3,Suggest,and,explain,a,procedure,the,scientist,could,have,used,to,stop,each,reaction.,,ANS,-,,-
,The,nature,of,the,enzyme,by,putting,it,in,ice.
1.4,Explain,the,change,in,ATP,concentration,with,increasing,inorganic,phosphate,concentration,,ANS,-,,-
,With,increasing,phosphate,concentration,more,ES,complex,is,form.
-,And,at,40,mol,dm3,,all,active,sites,are,occupied.
2.1,Explain,the,advantage,for,large,animals,of,having,a,specialised,system,that,facilitates,oxygen,uptake.,,
ANS,-,,-,Large,organisms,have,a,smaller,surface,area,to,volume,ratio.
-,This,means,they,overcome,a,long,diffusion,pathway.
2.2,Suggest,how,the,environmental,conditions,have,resulted,in,adaptations,of,systems,using,model,A,rat
her,than,model,B.,,ANS,-,,-,Water,is,more,dense,than,air.
-,So,it,supports,the,gills.
2.3,A,student,studies,figure,3,and,concluded,that,the,fish,gas,exchange,system,is,more,efficient,than,the,
human,gas,exchange,system.,Use,figure,3,to,justify,this,conclusion.,,ANS,-,,-
,The,difference,of,oxygen,concentration,between,the,artery,and,vein,is,larger,in,the,fish,than,the,human.
-,So,the,fish,remove,a,greater,amount,of,oxygen,that,they,intake.
, 2.4,Explain,how,the,countercurrents,principle,allows,sufficient,oxygen,uptake,in,the,fish,gas,exchange,sys
tem.,,ANS,-,,-,Blood,and,water,continuously,flow,in,opposite,directions.
-,So,the,concentration,gradient,is,maintained,along,the,length,of,the,lamellae.
3.1,Describe,how,one,amino,acid,is,added,to,a,polypeptide,that,is,being,formed,at,a,ribosome,during,tra
nslation.,,ANS,-,,-,TRNA,brings,the,specific,amino,acid,to,the,ribosome.
-,The,anticodon,on,the,tRNA,binds,to,the,codon,on,the,mRNA.
-,The,amino,acids,join,to,form,a,peptide,bond,using,ATP.
3.2,Use,information,in,table,to,to,suggest,why,this,amino,acid,replacement,changes,the,properties,of,cry
stallin.,,ANS,-,,-,The,hydrogen,bonds,form,instead,of,the,ionic,bonds.
-,And,it,changes,the,tertiary,structure,of,the,crystallin.
3.3,MRNA,codon,for,the,non-mutant,triplets.,
mutated,mRNA,codon.,
Mutated,DNA,triplet.,,ANS,-,,-,AGG
-,GGG
-,CCC
4.1,Suggest,two,ways,the,student,could,improve,the,quality,of,his,scientific,drawing,of,the,blood,vessels,i
n,this,dissection.,,ANS,-,,-,Add,labels.
-,Don't,use,shading.
4.2,Describe,one,feature,that,allows,you,to,identify,the,blood,vessels.
Blood,vessel,X
Blood,vessel,Y
Feature,,ANS,-,,-,Artery
-,Vein
-,They,have,different,wall,thicknesses.
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