AQA A LEVEL BIOLOGY 7402/3 Paper 3 June 2025 Actual
Exam 2026/2027 | Complete Exam-Style Questions with
Detailed Rationales | Pass Guaranteed – A+ Graded
Materials
For this paper you must have:
● a ruler with millimetre measurements
● a scientific calculator
Instructions
● Use black ink or black ball-point pen.
● Fill in the boxes at the top of this page.
● Answer all questions in Section A.
● Answer one question from Section B.
● You must answer the questions in the spaces provided. Do not write outside the
box around each page or on blank pages.
● If you need extra space for your answer(s), use the lined pages at the end of this
book. Write the question number against your answer(s).
● Do all rough work in this book. Cross through any work you do not want to be
marked.
● Show all your working.
Information
● The marks for questions are shown in brackets.
● The maximum mark for this paper is 78.
● You are expected to use a calculator where appropriate.
● A Data and Formulae Booklet is provided as a loose insert.
Advice
● In calculations show clearly how you work out your answer.
, ● Read each question carefully before you start to answer it.
● Keep an eye on the time.
● Try to answer every question.
● Check your answers if you have time at the end.
SECTION A: STRUCTURED QUESTIONS (38 marks)
Answer ALL questions in this section.
Q1: Enzyme Kinetics and Practical Technique (5 marks)
A student investigated the effect of substrate concentration on the rate of an
enzyme-controlled reaction using the enzyme catalase and hydrogen peroxide solution.
The student measured the initial rate of reaction by recording the volume of oxygen
produced in 30 seconds at each substrate concentration.
The student used a 1.0 mol dm⁻³ stock solution of hydrogen peroxide to prepare a
dilution series. The table shows the student's results.
Table
Hydrogen peroxide concentration (mol dm⁻³) Volume of oxygen produced in 30 s (cm³)
0.0 0.0
0.2 4.5
, 0.4 8.2
0.6 10.8
0.8 12.1
1.0 12.5
Q1(a) Describe how the student could have used the stock solution to prepare 20 cm³ of
the 0.2 mol dm⁻³ hydrogen peroxide solution. [2 marks]
Q1(b) Explain why the student measured the volume of oxygen produced in the first 30
seconds rather than over a longer time period. [2 marks]
Q1(c) Calculate the initial rate of reaction at 0.4 mol dm⁻³ hydrogen peroxide
concentration. Give your answer in cm³ s⁻¹. [1 mark]
MARK SCHEME Q1:
Q1(a)
● Take 4 cm³ of stock solution / 1.0 mol dm⁻³ solution and add (16 cm³) water to
make total volume 20 cm³; [1]
● Use of measuring cylinder / pipette / burette for accurate volume measurement;
[1]
Q1(b)
● (To measure) initial rate / rate at start of reaction; [1]
● Because substrate concentration decreases as reaction proceeds / product
concentration increases / enzyme may become denatured / reaction rate slows
down (over time); [1]
Exam 2026/2027 | Complete Exam-Style Questions with
Detailed Rationales | Pass Guaranteed – A+ Graded
Materials
For this paper you must have:
● a ruler with millimetre measurements
● a scientific calculator
Instructions
● Use black ink or black ball-point pen.
● Fill in the boxes at the top of this page.
● Answer all questions in Section A.
● Answer one question from Section B.
● You must answer the questions in the spaces provided. Do not write outside the
box around each page or on blank pages.
● If you need extra space for your answer(s), use the lined pages at the end of this
book. Write the question number against your answer(s).
● Do all rough work in this book. Cross through any work you do not want to be
marked.
● Show all your working.
Information
● The marks for questions are shown in brackets.
● The maximum mark for this paper is 78.
● You are expected to use a calculator where appropriate.
● A Data and Formulae Booklet is provided as a loose insert.
Advice
● In calculations show clearly how you work out your answer.
, ● Read each question carefully before you start to answer it.
● Keep an eye on the time.
● Try to answer every question.
● Check your answers if you have time at the end.
SECTION A: STRUCTURED QUESTIONS (38 marks)
Answer ALL questions in this section.
Q1: Enzyme Kinetics and Practical Technique (5 marks)
A student investigated the effect of substrate concentration on the rate of an
enzyme-controlled reaction using the enzyme catalase and hydrogen peroxide solution.
The student measured the initial rate of reaction by recording the volume of oxygen
produced in 30 seconds at each substrate concentration.
The student used a 1.0 mol dm⁻³ stock solution of hydrogen peroxide to prepare a
dilution series. The table shows the student's results.
Table
Hydrogen peroxide concentration (mol dm⁻³) Volume of oxygen produced in 30 s (cm³)
0.0 0.0
0.2 4.5
, 0.4 8.2
0.6 10.8
0.8 12.1
1.0 12.5
Q1(a) Describe how the student could have used the stock solution to prepare 20 cm³ of
the 0.2 mol dm⁻³ hydrogen peroxide solution. [2 marks]
Q1(b) Explain why the student measured the volume of oxygen produced in the first 30
seconds rather than over a longer time period. [2 marks]
Q1(c) Calculate the initial rate of reaction at 0.4 mol dm⁻³ hydrogen peroxide
concentration. Give your answer in cm³ s⁻¹. [1 mark]
MARK SCHEME Q1:
Q1(a)
● Take 4 cm³ of stock solution / 1.0 mol dm⁻³ solution and add (16 cm³) water to
make total volume 20 cm³; [1]
● Use of measuring cylinder / pipette / burette for accurate volume measurement;
[1]
Q1(b)
● (To measure) initial rate / rate at start of reaction; [1]
● Because substrate concentration decreases as reaction proceeds / product
concentration increases / enzyme may become denatured / reaction rate slows
down (over time); [1]
