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Practise 40 exam-style questions on Photosynthetic reaction 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.
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.
Name the leaf tissue that contains the most chloroplasts.
Palisade mesophyll
Palisade mesophyll cells are packed with chloroplasts and are the main sites of photosynthesis in the leaf.
palisade mesophyll
Allow palisade cells
Explain why algae in ponds may increase oxygen concentration during the day but decrease it at night.
During the day algae photosynthesise and produce O2; at night photosynthesis stops but respiration continues, consuming O2, so oxygen decreases.
Photosynthesis adds oxygen when light is available; in darkness only respiration consumes oxygen.
day: photosynthesis produces O2
night: photosynthesis stops but respiration continues so O2 is used
A student places potted plants in a growth chamber and reduces CO2 concentration. Explain the effect this would have on photosynthesis and plant growth.
Lower CO2 reduces rate of photosynthesis (CO2 becomes limiting) so less glucose produced; less respiration and building materials result in slower growth and lower biomass.
CO2 is a substrate for the Calvin cycle; reducing its concentration lowers carbohydrate production and hence growth.
decreased photosynthesis / rate falls
less glucose / less building materials / less respired energy
reduced growth / less biomass
Write the symbol equation for photosynthesis. Use chemical symbols and the word light.
CO2 + H2O + light ? C6H12O6 + O2
Photosynthesis uses carbon dioxide and water with light energy to make glucose (C6H12O6) and oxygen (O2). Each chemical symbol must be correct to score the mark.
CO2
H2O
C6H12O6
Accept C6H12O6
O2
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