AQA A-Level Biology: Paper 1 2024
1.1 Describe the induced fit model of enzyme action and
how an enzyme acts as a catalyst. -CORRECT
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
produce ATP. -CORRECT ANS-- Adenosine diphosphate.
1.3 Suggest and explain a procedure the scientist could have used to stop each reaction. -CORRECT
ANS-- The nature of the enzyme by putting it in ice.
1.4 Explain the change in ATP concentration with increasing inorganic phosphate concentration -
CORRECT 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.
-CORRECT 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
rather than model B. -CORRECT 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. -CORRECT 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
system. -CORRECT 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
translation. -CORRECT 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
crystallin. -CORRECT 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. -CORRECT ANS-- AGG
- GGG
- CCC
4.1 Suggest two ways the student could improve the quality of his scientific drawing of the blood vessels
in this dissection. -CORRECT 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 -CORRECT ANS-- Artery
- Vein
- They have different wall thicknesses.
1.1 Describe the induced fit model of enzyme action and
how an enzyme acts as a catalyst. -CORRECT
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
produce ATP. -CORRECT ANS-- Adenosine diphosphate.
1.3 Suggest and explain a procedure the scientist could have used to stop each reaction. -CORRECT
ANS-- The nature of the enzyme by putting it in ice.
1.4 Explain the change in ATP concentration with increasing inorganic phosphate concentration -
CORRECT 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.
-CORRECT 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
rather than model B. -CORRECT 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. -CORRECT 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
system. -CORRECT 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
translation. -CORRECT 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
crystallin. -CORRECT 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. -CORRECT ANS-- AGG
- GGG
- CCC
4.1 Suggest two ways the student could improve the quality of his scientific drawing of the blood vessels
in this dissection. -CORRECT 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 -CORRECT ANS-- Artery
- Vein
- They have different wall thicknesses.
