OCR A Level Biology Paper 1, Biological Processes (H420/01), from June 2025 covers Modules 1, 2, 3 and 5: 100 marks in 2 hours 15 minutes, starting with 15 multiple-choice questions. The question paper, mark scheme and examiners’ report are on the OCR past papers page, with a self-marking quiz of the multiple-choice section.
What the paper tested
Transport in animals was the big topic, 21 marks, most of them in Question 20 (blood vessels, the cardiac cycle and a 6-mark ECG question) and Question 21. Photosynthesis took 15 marks across Questions 16 and 19, enzymes 12 in Question 17 (regulation of glycolysis by PFK), and plant responses 8 in Question 18, which also carried a 6-mark statistical evaluation of a gibberellin experiment. Practical skills were worth about 20 marks in total: chromatography (PAG 6), plant responses (PAG 11), a colorimeter or potometer (PAG 5) and standard deviation and the t-test.
Start with the transport in animals written quiz, the photosynthesis written quiz and the enzymes written quiz, which mark your answers against the mark scheme as you go.
Where students lost marks
OCR’s report does not give percentages, but it says clearly which parts caused trouble and why.
18(b) Evaluating a gibberellin experiment with a t-test (6 marks)
Most students stated a null hypothesis and rejected it, but few calculated the degrees of freedom correctly. This was an unpaired t-test with two independent groups of eight plants, so the degrees of freedom are (8 + 8) − 2 = 14; many used a different number and read the wrong critical value. Very few noticed that the control group was poorly described: a control must match the experimental group in everything except the factor under test, so the control plants should have been sprayed with the same solution minus gibberellin.
20(d) Initiating the heartbeat and the ECG (6 marks)
Good answers linked the SAN, AVN, bundle of His and Purkyne fibres to the P, QRS and T waves in turn. Weaker answers confused the ECG with pressure changes, wrote about ‘signals’ rather than impulses or waves of excitation, or ignored ‘at rest’ and discussed the medulla and the sympathetic nervous system. Few mentioned that cardiac muscle is myogenic, which is where the answer should begin.
17(a)(ii) and 17(a)(v) PFK and the regulation of glycolysis (3 and 2 marks)
The explanation of non-competitive inhibition was generally well done, though a few students called the allosteric site a ‘second active site’. The harder part was 17(a)(v): using the information that AMP reverses ATP’s inhibition of PFK to explain how PFK regulates the rate of glycolysis. Many wrote about needing ATP for energy rather than about rate, which was the word in the question.
17(c)(iii) Oxidation in glycolysis (2 marks)
Most gained a mark for NAD being reduced, but struggled to say how. The examiners flagged a common misconception: describing oxidation only as loss of electrons does not explain NADH, which forms when NAD gains both electrons and a hydrogen ion. The {a('/tutoring-blog/ocr-a-level-biology-respiration-written-questions','respiration written quiz')} has several questions on this.
20(a) Matching blood vessel features (3 marks)
Few students matched all three descriptions to the right vessel type. Most recognised the capillaries, then lost marks by listing the vessel types under the table without matching them to the descriptions asked for.
18(c) Gibberellin inhibitors and crop yield (3 marks)
Most understood that shorter stems would not fall over, but few explained why standing plants give a higher yield, and very few picked up that the question said production of gibberellin was inhibited, not its release, so the concentration of the hormone would fall.
16(a)(ii) Chloroplasts and mitochondria (2 marks)
A simple-looking question on one structural similarity and one difference. Errors included calling the membranes ‘plasma membranes’, saying chloroplasts have no DNA, and giving starch as a structural difference when it is a product.
How to use this paper
Sit it in one go, 2 hours 15 minutes, then mark it. The multiple-choice section is also on the quiz page if you want to retry it quickly.
For each part you dropped marks on, read the examiners’ comment. On this paper the recurring faults were terminology (‘signals’, ‘second active site’), skipped calculation steps (degrees of freedom) and not answering the word that mattered (‘rate’, ‘at rest’, ‘production’).
Work the big topics with the OCR exam questions by topic and the written quizzes, then come back to the paper later in the year.
Convert your mark with the OCR grade boundaries.
Questions and examiners’ comments are summarised from OCR’s published question paper, mark scheme and report for H420/01 June 2025, © OCR.