OCR A 5.2.1 · 20 written questions · 49 marks · about 60 minutes · marked as you go
This free quiz has 20 written exam questions on photosynthesis, all taken from OCR A Level Biology A papers (A level, 2017 to 2025). 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 photosynthesis, from the link with respiration and chloroplast structure through pigments and TLC, the light-dependent stage and the Calvin cycle to limiting factors.
What the quiz covers (OCR A spec 5.2.1)
Photosynthesis and respiration (5.2.1(a)): how the raw materials and products of the two processes are linked, using a sealed terrarium and respirometer data.
Chloroplast structure (5.2.1(b)): labelling a TEM of a chloroplast, where the pigments sit, and comparing chloroplasts with mitochondria.
Photosynthetic pigments and TLC (5.2.1(c)): the roles of primary and accessory pigments, the stationary phase, calculating an Rf value and improving faint spots.
The light-dependent stage (5.2.1(d)): the final electron acceptor, drawing conclusions from a Hill reaction experiment, and what happens when excess light energy is lost as heat.
The Calvin cycle and triose phosphate (5.2.1(e)–(f)): RuBP, RuBisCO, GP and TP, Calvin's radioactive carbon experiment and the molecules made from TP.
Factors affecting photosynthesis (5.2.1(g)): defining a limiting factor, reading limiting factor graphs, a pondweed temperature investigation, changes in RuBP and GP when CO₂ falls, and why temperature matters most for the light-independent stage.
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 12-question Photosynthesis multiple choice quiz first.
Open the Photosynthesis 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.
Compare like with like: When data compare GM and unmodified plants, students compared the GM plant at two different times and concluded that genetic modification decreased carbon fixation.
✔ Gains credit: At 150 seconds the GM plants have a higher rate of CO₂ fixation than the unmodified plants.
Link less heat loss to ATP: Students said the GM plants fixed more CO₂ because of lower NPQ, but stopped there without explaining how that helps the Calvin cycle.
✔ Gains credit: Less light energy is converted to heat, so more electrons enter the electron transport chain and more ATP and reduced NADP are supplied to the Calvin cycle.
Thylakoid membranes, inside photosystems: Asked for the precise location of the pigments, students wrote 'grana' or just 'the chloroplast', which is not precise enough.
✔ Gains credit: The pigments are in the photosystems (light-harvesting systems) in the thylakoid membranes.
NADP, not NADPH, accepts electrons: Students named NADPH or reduced NADP as the final electron acceptor, but that is what the acceptor becomes after it has accepted the electrons.
✔ Gains credit: NADP (NADP⁺) is the final electron acceptor in the light-dependent stage.
Temperature doesn't excite enzymes: Answers on temperature were vague, or said temperature 'excites' the enzymes, and many forgot about denaturation at high temperatures.
✔ Gains credit: The light-independent stage is controlled by enzymes such as RuBisCO; higher temperature increases their kinetic energy so more enzyme-substrate complexes form, but high temperatures denature them.
Say what the plateau rules out: Students compared the CO₂ lines on a light intensity graph but ignored what the levelling off shows about light.
✔ Gains credit: Where the rate plateaus, light intensity is no longer the limiting factor; the higher plateau with more CO₂ at the same temperature shows CO₂ is limiting.
Deep water filters out wavelengths: Students knew algae live in water but didn't explain why that needs different pigments.
✔ Gains credit: Only shorter wavelengths of light (such as blue) reach deep water, so the alga needs pigments that absorb those wavelengths.
Limiting means it stops the rate rising: Students defined a limiting factor as something that 'inhibits' or 'reduces' the rate, which OCR does not allow.
✔ Gains credit: The factor in shortest supply, which prevents the rate of photosynthesis from increasing.
Keep practising
Try the Photosynthesis multiple choice quiz, the Respiration multiple choice quiz, the Plant and Animal Responses written quiz or the Respiration 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.