Practise 40 exam-style questions on Rate of photosynthesis for AQA GCSE Biology. Write your answer as you would in the exam and get it marked in seconds against the mark scheme, point by point, with an AI tutor on hand if you get stuck.
40 questions
1–6 marks each
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20 questions, marked as you go
Sample questions with model answers
Here are 4 of the questions in this topic, each with a model answer, an explanation of why it earns the marks and the mark scheme an examiner would use.
Question 1
2 marks
Describe one advantage and one disadvantage of increasing greenhouse light intensity to maximise photosynthesis.
Model answer
Advantage: increases photosynthetic rate and crop yield. Disadvantage: higher energy costs (electricity for lamps) may reduce profit; risk of overheating.
Explanation
More light can drive higher photosynthesis and bigger yields, but artificial lighting costs money and can heat the greenhouse, so economic and temperature factors limit excessive lighting.
Mark scheme
1 mark
advantage: increases rate / yield
1 mark
disadvantage: higher energy cost / cost may outweigh profit (or overheating)
Question 2
3 marks
A student uses a light meter and records light intensity at distances 10 cm, 20 cm and 30 cm from a lamp. Predict the relative light intensities using the inverse square law (express as relative numbers with intensity at 10 cm = 1).
Model answer
Intensity ? 1/d² so at 10 cm = 1; at 20 cm intensity = 1/(2)² = 1/4 = 0.25; at 30 cm = 1/(3)² = 1/9 ˜ 0.11.
Explanation
Using I ? 1/d², if I at 10 cm is 1 then at 20 cm (double the distance) intensity is 1/4, and at 30 cm (triple) it is 1/9 (~0.11).
Mark scheme
1 mark
statement: intensity ? 1/distance²
1 mark
20 cm = 1/4
1 mark
30 cm = 1/9 (˜0.11)
Question 3
3 marks
A student measures starch production in two leaves: one exposed to light all day and one kept in shade. Predict the relative starch amounts and justify using photosynthesis concepts.
Model answer
Leaf in full light will have more starch because photosynthesis produces glucose which is converted to starch; shaded leaf has low light so less photosynthesis and less starch accumulation.
Explanation
Light drives photosynthesis to make sugars; leaves with more light produce more sugars which are stored as starch. Shade reduces light-driven sugar production, so less starch forms.
Mark scheme
1 mark
leaf in light has more starch than shaded leaf
1 mark
photosynthesis in light produces glucose
1 mark
glucose converted to starch for storage so more photosynthesis -> more starch
Question 4
4 marks
Explain why water stress (drought) reduces photosynthesis in leaves, mentioning stomata and biochemical effects.
Model answer
Drought causes stomata to close to reduce water loss, which reduces CO2 uptake and lowers photosynthesis. Prolonged water stress can damage enzymes and reduce chlorophyll, further reducing photosynthetic capacity.
Explanation
To conserve water plants close stomata, but this limits CO2 entry so the Calvin cycle slows. Severe drought also affects cell biochemistry and chlorophyll levels, further reducing photosynthesis.
Mark scheme
2 marks
stomatal closure reduces CO2 diffusion into leaf so less CO2 for photosynthesis
Award up to 2 marks for stomata and CO2 link.
2 marks
biochemical effects: enzyme activity reduced or chlorophyll decreased/damage to photosynthetic machinery under prolonged stress
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