Disclaimer: This document was created by department heads with many years of experience teaching the
AQA A Level Biology course. We cannot however guarantee that it is an accurate representation of the
Summer 2025 examinations and students should not treat it as such. Please use this as an aid, alongside other
methods of revision.
AQA A Level
Thursday 5 June 2025
Afternoon (Time: 2 hours)
Biology
Unit: 7402/1
Paper 1
You must have:
Calculator, ruler
Instructions
• Use black ink or a ball-point pen.
• Answer all questions.
• Answer the questions in the spaces provided.
○ There may be more space than you need.
• Show all the steps in any calculations and state the units.
Information
• The total mark for this paper is 91.
• The marks for each question are shown in brackets.
○ Use this as a guide as to how much time to spend on each question.
Advice
• Read each question carefully before you start to answer it.
• Write your answers neatly and in good English.
• Try to answer every question.
• Check your answers if you have time at the end.
Turn over →
© 2025 Empirical Tuition. All rights reserved.
, Answer all questions.
1. Methotrexate is a drug that is used to inhibit the enzyme dihydrofolate reductase. Methotrexate
is an example of a competitive inhibitor.
(a) Describe how a competitive inhibitor can reduce the rate of an enzyme-controlled reaction. (3)
Dihydrofolate reductase (DR) is involved in the synthesis of DNA nucleotides. A graph showing the
inhibition of DR with methotrexate is shown below.
2
, (b) Explain how the graph shows that methotrexate is a competitive inhibitor. (1)
A scientist decides to compare the rate of nucleotide synthesis with and without methotrexate. To
do this he uses the following equation:
𝑉𝑚𝑎𝑥 × [𝑆]
𝑉=
𝐾𝑚 + [𝑆]
Where: Vmax = the maximum reaction velocity (120 mmol/min), Km = the Michaelis constant (0.2
mM without methotrexate and 0.5 mM with methotrexate) and [S] = the substrate concentration.
(c) Calculate the reaction velocity (V) for both scenarios (with and without methotrexate) when the
dihydrofolate concentration is 0.1 mM. (4)
(d) Suggest how methotrexate might be used to treat certain types of cancers. (3)
3
AQA A Level Biology course. We cannot however guarantee that it is an accurate representation of the
Summer 2025 examinations and students should not treat it as such. Please use this as an aid, alongside other
methods of revision.
AQA A Level
Thursday 5 June 2025
Afternoon (Time: 2 hours)
Biology
Unit: 7402/1
Paper 1
You must have:
Calculator, ruler
Instructions
• Use black ink or a ball-point pen.
• Answer all questions.
• Answer the questions in the spaces provided.
○ There may be more space than you need.
• Show all the steps in any calculations and state the units.
Information
• The total mark for this paper is 91.
• The marks for each question are shown in brackets.
○ Use this as a guide as to how much time to spend on each question.
Advice
• Read each question carefully before you start to answer it.
• Write your answers neatly and in good English.
• Try to answer every question.
• Check your answers if you have time at the end.
Turn over →
© 2025 Empirical Tuition. All rights reserved.
, Answer all questions.
1. Methotrexate is a drug that is used to inhibit the enzyme dihydrofolate reductase. Methotrexate
is an example of a competitive inhibitor.
(a) Describe how a competitive inhibitor can reduce the rate of an enzyme-controlled reaction. (3)
Dihydrofolate reductase (DR) is involved in the synthesis of DNA nucleotides. A graph showing the
inhibition of DR with methotrexate is shown below.
2
, (b) Explain how the graph shows that methotrexate is a competitive inhibitor. (1)
A scientist decides to compare the rate of nucleotide synthesis with and without methotrexate. To
do this he uses the following equation:
𝑉𝑚𝑎𝑥 × [𝑆]
𝑉=
𝐾𝑚 + [𝑆]
Where: Vmax = the maximum reaction velocity (120 mmol/min), Km = the Michaelis constant (0.2
mM without methotrexate and 0.5 mM with methotrexate) and [S] = the substrate concentration.
(c) Calculate the reaction velocity (V) for both scenarios (with and without methotrexate) when the
dihydrofolate concentration is 0.1 mM. (4)
(d) Suggest how methotrexate might be used to treat certain types of cancers. (3)
3
