AQA A Level Biology Paper 1 (7402/1) from June 2025 is the most recent Paper 1 you can sit under exam conditions. It is 91 marks in 2 hours and covers topics 3.1 to 3.4 plus practical skills. The question paper, mark scheme and examiners’ report are all on the AQA past papers page. This guide tells you what the paper tested, where students lost marks according to the examiners, and what to practise before you try it.
What the paper tested
Cells carried the most marks: about 13 on cell structure (a long Question 9 on organelles and micrographs) and 11 on transport across membranes (Question 5 on carrier proteins in ripening pears, plus 1.2 on the phospholipid bilayer). Proteins and enzymes took 11 marks, almost all in Questions 2 and 3, including a comparison of the lock-and-key and induced-fit models and a practical on competitive inhibition of lactase. DNA and protein synthesis had 9 marks, with a 6-mark extended answer at 10.1. Mass transport (7 marks, including the crab haemocyanin data in Question 6), mutation and meiosis (7 marks in Question 7) and the usual smaller slices of digestion, gas exchange and carbohydrates made up the rest.
Practise the big topics first: cell structure questions, transport across membranes questions, enzymes questions and proteins questions, each with the mark scheme and the examiners’ tips.
Where students lost marks
The examiners’ report gives the proportion of students reaching each mark on most questions. These are the parts where the fewest did, with the reasons the examiners gave.
6.1 Haemocyanin dissociation curves (2 marks)
Fewer than one student in ten scored both marks. The question showed oxyhaemocyanin curves for a crab at two temperatures and asked how a rise in temperature affects oxygen loading in the gills and unloading in the tissues. Most students could not place the gills and the tissues on the partial-pressure axis, so they wrote general statements about affinity instead of reading the graph. The point the examiners wanted was that at the gills, where the partial pressure of oxygen is high, the two curves are almost together, so loading barely changes, while at the tissues the warmer curve is lower, so more oxygen is unloaded. Dissociation-curve questions are always about reading the curve at the right place; our {a('/tutoring-blog/2024/3/1/transport-in-animals-understanding-haemoglobin-cooperative-binding-and-oxygen-dissociation-curves','haemoglobin and the Bohr effect')} explainer and the {a('/aqa-exam-questions/aqa-a-level-biology-haemoglobin-questions','haemoglobin questions')} cover exactly this.
6.4 Evaluating how data were presented (3 marks)
Under 5% of students got full marks. Students had the raw data points behind a mean-value graph and were asked to assess whether the way the data were presented was valid. Most wrote the familiar lines about only three running speeds and a small sample, which earned little. What the examiners wanted was comment on the figure itself: the number of crabs at each speed varied a lot, the ranges of the groups did not overlap, and the graph already used means. Suggestions such as adding error bars or removing anomalies did not fit the data shown. The lesson is to look at the actual figure before reaching for stock evaluation phrases.
3.4 Modifying a practical to confirm competitive inhibition (2 marks)
About a quarter of students scored both marks. To show that galactose is a competitive inhibitor of lactase you increase the substrate concentration and expect the rate to recover towards the uninhibited value. Many students changed the galactose or lactose concentration in a way that only altered the degree of inhibition, which does not distinguish competitive from non-competitive inhibition. The {a('/aqa-exam-questions/aqa-a-level-biology-required-practical-1-enzymes-questions','Required Practical 1 questions')} are good preparation for this kind of ‘change the method’ question.
7.4 Non-disjunction (3 marks)
Only about 5% of students scored all three marks, almost always because they missed the last point. Most named non-disjunction and said that homologous chromosomes or chromatids failed to separate, but very few went on to explain that both chromosomes or both chromatids then moved to the same pole, or that spindle fibres had failed, so one gamete gained a chromosome. Restating the question (‘the cell ends up with an extra chromosome’) earned nothing.
10.2 Leaf adaptations for gas exchange (4 marks)
About 5% of students scored four marks. Nearly everyone gained a mark for many stomata and for thin leaves giving a short diffusion pathway. The two marks that were rarely given were for the large surface area of the spongy mesophyll cells themselves, rather than of the whole leaf, and for linking a large surface area to volume ratio explicitly to diffusion. Writing ‘for gas exchange’ at the end of a point was not enough; the examiners wanted ‘diffusion’.
8.5 Bacterial growth and plasmid copy number (3 marks)
Fewer than one in ten students scored full marks and the mean was about 1 out of 3. The graph had two dependent variables and students were expected to link the rise in cloudiness to binary fission and the rise in plasmid copy number to plasmid replication. Answers that simply described the data without explaining it scored zero.
5.3 Gene expression and carrier proteins (2 marks)
The question asked how a change in gene expression could speed up ripening. The intended answer was simple: more expression means more carrier proteins, so faster movement of ions and sugars across the membrane. Many students instead wrote about a mutation in a gene, which is not a change in expression, and lost both marks.
Maths and practical skills on this paper
Plotting and interpreting graphs carried about 12 marks, percentages and ratios 9, and evaluating experimental design 8. The calculations themselves (3.2, 6.3, 7.1, 8.2, 8.4) were accessible, with 90% of students getting the dilution volume in 3.2 right, but the examiners noted rounding errors and students who had clearly not met the practical context before. The handling data and graph skills question sets are built from questions like these.
How to use this paper
Sit it in one go, 2 hours, no notes. Mark it strictly against the mark scheme.
For every part where you dropped marks, read the examiners’ comment on that question. The report is written for teachers but the reasons marks were lost are plain.
Then work the topic, not the paper: the AQA exam questions by topic give you more questions on the same spec point with the mark scheme beside each one, and the AQA quizzes are a quick check that the knowledge has stuck.
Check how your mark converts with the AQA grade boundaries: in June 2025 Paper 1 contributed 91 of the 260 raw marks.
Questions and examiners’ comments are summarised from AQA’s published question paper, mark scheme and report for 7402/1 June 2025, © AQA. Figures quoted are AQA’s.