OCR A 5.2.2 · 20 written questions · 42 marks · about 50 minutes · marked as you go
This free quiz has 20 written exam questions on respiration, all taken from OCR A Level Biology A papers (A level, 2017 to 2025, plus OCR practice or sample papers). Short answers mark themselves. For longer answers you write your answer, then tick off the OCR mark-scheme points you made, so you see exactly where the marks are. Twenty real OCR A Level Biology exam questions on respiration, from why cells need ATP and the structure of the mitochondrion through glycolysis, the link reaction, the Krebs cycle and chemiosmosis to anaerobic respiration and RQ.
What the quiz covers (OCR A spec 5.2.2)
Why cells respire and the mitochondrion (5.2.2(a)–(b)): why processes need ATP, labelling mitochondria in a sperm cell and linking membrane structure to function.
Glycolysis and the link reaction (5.2.2(c)–(d)): the type of reaction catalysed by PFK, how oxidation happens in glycolysis, and where and how CO₂ is released.
The Krebs cycle and coenzymes (5.2.2(e)–(f)): substrate-level phosphorylation, the reactions between intermediates, and what NAD and FAD do in beta oxidation.
Oxidative phosphorylation and chemiosmosis (5.2.2(g)–(h)): where FAD is reduced and oxidised, how ATP synthase makes ATP, and Jagendorf's thylakoid experiment.
Anaerobic respiration and yeast practicals (5.2.2(i)): interpreting a yeast batch culture graph and completing a method for comparing yeast respiration rates.
Respiratory substrates and RQ (5.2.2(j)–(k)): why fatty foods release more energy, using RQ values to deduce diets, and RQ changes during exercise.
How to use it
Write every answer in full, as you would in the exam: the mark for each question is shown, so you know how much to write. When you self-mark, only tick a point if your answer clearly makes it, then read the examiner's tip under each question. Your progress is saved on your device, so you can do it in two sittings, and at the end you can retry just the questions where you dropped marks.
Prefer multiple choice? Try the 17-question Respiration multiple choice quiz first.
Open the Respiration quiz in a new tab (easier on a phone)
Where students lose marks (from OCR examiners' reports and mark schemes)
Each point below is followed by wording that gained marks.
Glucose first, then ethanol: On a yeast batch culture graph, many wrote from memory that yeast respires aerobically then anaerobically, ignoring what the graph actually showed.
✔ Gains credit: Anaerobic respiration of glucose to ethanol happened first; once the glucose was used up, the yeast respired the ethanol aerobically.
No gradient, no ATP: Students said thylakoids in the more acidic solution would make more ATP because there are more H⁺ ions, missing that the inside of the thylakoids was already at the same pH.
✔ Gains credit: ATP is only made where there is a proton gradient between the thylakoid space and the solution, so protons can diffuse out through ATP synthase.
RQ 0.8 isn't always protein: When RQ rose from 0.7 during exercise, many said protein was being respired at 0.8 instead of seeing a shift from fat towards carbohydrate.
✔ Gains credit: Lipids have an RQ of about 0.7 and carbohydrate 1.0, so a rising RQ means more carbohydrate is being used, with some fat still respired.
Calculate the RQ to justify: Students justified a diet in words (more oxygen used than CO₂ made) without any calculated values, and some confused protein with lipid.
✔ Gains credit: Calculate RQ = CO₂ produced ÷ O₂ consumed for each organism, then match the value to the respiratory substrate.
Pumped out, diffuse back: Students wrote that protons are pumped through ATP synthase, or that energy is 'produced' to join ADP and Pi.
✔ Gains credit: Protons are pumped into the intermembrane space, then flow down their concentration gradient through ATP synthase into the matrix, providing energy to join ADP and Pi.
No ATP from the link reaction: When describing substrate-level phosphorylation, some said ATP is made in the link reaction, or described oxidative phosphorylation instead.
✔ Gains credit: Substrate-level phosphorylation happens in glycolysis (when triose phosphate is converted to pyruvate) and once per turn of the Krebs cycle.
Don't reuse the question's example: Asked for another way ATP contributes to respiration, many repeated the glycolysis example already given, or named moving pyruvate into mitochondria without saying 'active transport'.
✔ Gains credit: ATP is used for the active transport of pyruvate into the mitochondrion, or to synthesise respiratory enzymes.
Get the protons into the thylakoid: Students described what H⁺ ions do inside the chloroplast without first explaining how they leave the solution and get there.
✔ Gains credit: Protons diffuse down their concentration gradient into the chloroplasts and are moved into the thylakoid space, so the pH of the solution rises.
Keep practising
Try the Respiration multiple choice quiz, the Photosynthesis multiple choice quiz, the Photosynthesis written quiz, or browse all our OCR A Level Biology quizzes. Our OCR A masterclasses (Year 12 on Wednesdays at 5.15pm, Year 13 on Tuesdays at 6.30pm) work through real exam questions on one topic each week.
Questions, mark schemes and examiners' report extracts © OCR.