ACTUAL 2025 AQA A-LEVEL BIOLOGY Paper 3
Question Paper & Mark Scheme (Merged) Wednesday 18 June 2025 [VERIFIED]
, 2
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
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IB/M/Jun25/7402/3
, 3
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outside the
box
0 1 . 2 Microbiologists investigated the effect of two temperatures on the population growth of 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
, 4
Do not write
outside the
The bacterial population at 24 °C is larger than that at 20 °C Calculate this box
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 =
3
0 1 . 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]
IB/M/Jun25/7402/3
Question Paper & Mark Scheme (Merged) Wednesday 18 June 2025 [VERIFIED]
, 2
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
, 3
Do not write
outside the
box
0 1 . 2 Microbiologists investigated the effect of two temperatures on the population growth of 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
, 4
Do not write
outside the
The bacterial population at 24 °C is larger than that at 20 °C Calculate this box
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 =
3
0 1 . 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]
IB/M/Jun25/7402/3
