AQA A-LEVE BIOLOGY Paper 3 JUNE 2025 Combined Question Paper and
Mark Scheme
Please write clearly in block capitals.
Centre number Candidate number
Surname
Forename(s)
Candidate signature
I declare this is my own work.
A-level
BIOLOGY
Paper 3
Wednesday 18 June 2025 Morning Time allowed: 2 hours
Materials For Examiner’s Use
For this paper you must have:
Question Mark
• a ruler with millimetre measurements
• a scientific calculator. 1
2
Instructions 3
• Use black ink or black ball-point pen.
• Fill in the boxes at the top of this page. 4
• Answer all questions in Section A. 5
• Answer one question from Section B. 6
• You must answer the questions in the spaces provided. Do not write
7
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 TOTAL
this book. Write the question number against your answer(s).
• Show all your working.
• Do all rough work in this book. Cross through any work you do not want
to be marked.
Information
• The marks for the questions are shown in brackets.
• The maximum mark for this paper is 78.
, 3
Do not write
outside the
Section A box
Answer all questions in this section.
You are advised to spend no more than 1 hour and 15 minutes on this section.
0 1 . 1 Describe binary fission in bacteria.
[3 marks]
Question 1 continues on the next page
Turn over ►
IB/M/Jun25/7402/3
, 4
Do not write
outside the
0 1 . 2 Microbiologists investigated the effect of two temperatures on the population growth of box
a species of bacterium.
They grew separate bacterial cultures in identical nutrient media at 20 °C and 24 °C
for 8 hours.
Figure 1 shows the estimated final population size of each culture.
Figure 1
IB/M/Jun25/7402/3
, 5
Do not write
outside the
The bacterial population at 24 °C is larger than that at 20 °C box
Calculate this difference as a percentage increase.
The actual number of bacteria can be calculated from the log10 value by using the
10x button on your calculator.
Give your answer to the nearest whole number.
Show your working.
[2 marks]
Percentage increase =
0 1 . 3 Bedaquiline is a drug that inhibits ATP synthase in mycobacteria by stopping
hydrogen ion (proton) movement.
Explain how bedaquiline can kill these bacteria.
[3 marks]
8
Turn over ►
IB/M/Jun25/7402/3
Mark Scheme
Please write clearly in block capitals.
Centre number Candidate number
Surname
Forename(s)
Candidate signature
I declare this is my own work.
A-level
BIOLOGY
Paper 3
Wednesday 18 June 2025 Morning Time allowed: 2 hours
Materials For Examiner’s Use
For this paper you must have:
Question Mark
• a ruler with millimetre measurements
• a scientific calculator. 1
2
Instructions 3
• Use black ink or black ball-point pen.
• Fill in the boxes at the top of this page. 4
• Answer all questions in Section A. 5
• Answer one question from Section B. 6
• You must answer the questions in the spaces provided. Do not write
7
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 TOTAL
this book. Write the question number against your answer(s).
• Show all your working.
• Do all rough work in this book. Cross through any work you do not want
to be marked.
Information
• The marks for the questions are shown in brackets.
• The maximum mark for this paper is 78.
, 3
Do not write
outside the
Section A box
Answer all questions in this section.
You are advised to spend no more than 1 hour and 15 minutes on this section.
0 1 . 1 Describe binary fission in bacteria.
[3 marks]
Question 1 continues on the next page
Turn over ►
IB/M/Jun25/7402/3
, 4
Do not write
outside the
0 1 . 2 Microbiologists investigated the effect of two temperatures on the population growth of box
a species of bacterium.
They grew separate bacterial cultures in identical nutrient media at 20 °C and 24 °C
for 8 hours.
Figure 1 shows the estimated final population size of each culture.
Figure 1
IB/M/Jun25/7402/3
, 5
Do not write
outside the
The bacterial population at 24 °C is larger than that at 20 °C box
Calculate this difference as a percentage increase.
The actual number of bacteria can be calculated from the log10 value by using the
10x button on your calculator.
Give your answer to the nearest whole number.
Show your working.
[2 marks]
Percentage increase =
0 1 . 3 Bedaquiline is a drug that inhibits ATP synthase in mycobacteria by stopping
hydrogen ion (proton) movement.
Explain how bedaquiline can kill these bacteria.
[3 marks]
8
Turn over ►
IB/M/Jun25/7402/3
