AQA A-Level Biology Paper 1 2021
Exam Question & Answers ( Latest
2025 )
1.1 Describe the induced fit model of enzyme action and
how an enzyme acts as a catalyst. - CORRECT
ANSWERS ✔✔- 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 ANSWERS ✔✔- Adenosine
diphosphate.
1.3 Suggest and explain a procedure the scientist could
have used to stop each reaction. - CORRECT ANSWERS
✔✔- The nature of the enzyme by putting it in ice.
1.4 Explain the change in ATP concentration with
increasing inorganic phosphate concentration - CORRECT
ANSWERS ✔✔- With increasing phosphate
concentration more ES complex is form.
- And at 40 mol dm3, all active sites are occupied.
, AQA A-Level Biology Paper 1 2021
Exam Question & Answers ( Latest
2025 )
2.1 Explain the advantage for large animals of having a
specialised system that facilitates oxygen uptake. -
CORRECT ANSWERS ✔✔- 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 ANSWERS ✔✔- 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 ANSWERS ✔✔- 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.
Exam Question & Answers ( Latest
2025 )
1.1 Describe the induced fit model of enzyme action and
how an enzyme acts as a catalyst. - CORRECT
ANSWERS ✔✔- 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 ANSWERS ✔✔- Adenosine
diphosphate.
1.3 Suggest and explain a procedure the scientist could
have used to stop each reaction. - CORRECT ANSWERS
✔✔- The nature of the enzyme by putting it in ice.
1.4 Explain the change in ATP concentration with
increasing inorganic phosphate concentration - CORRECT
ANSWERS ✔✔- With increasing phosphate
concentration more ES complex is form.
- And at 40 mol dm3, all active sites are occupied.
, AQA A-Level Biology Paper 1 2021
Exam Question & Answers ( Latest
2025 )
2.1 Explain the advantage for large animals of having a
specialised system that facilitates oxygen uptake. -
CORRECT ANSWERS ✔✔- 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 ANSWERS ✔✔- 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 ANSWERS ✔✔- 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.
