The light-independent stage and limiting factorsEdexcel A-Level Biology B: Mind map

Exam questions on The light-independent stage and limiting factors

1. Cells of the green alga Chlorella were kept in bright light with a constant supply of carbon dioxide, so that the Calvin cycle was running steadily. The light was then switched off while the carbon dioxide supply continued, and the concentrations of ribulose bisphosphate (RuBP) and glycerate 3-phosphate (GP) in the cells were measured.
   Explain the changes in the concentrations of GP and RuBP after the light was switched off.2 marks
2. A grower produces tomatoes in a glasshouse. In winter she adds carbon dioxide to the air, uses artificial lighting and heats the glasshouse, but keeps the temperature below 35 °C.
   The grower finds that raising the temperature from 15 °C to 25 °C increases the rate of photosynthesis when light and carbon dioxide are plentiful. Explain why.2 marks
3. A leaf was illuminated at a constant light intensity and a constant temperature of 25 °C. The rate of photosynthesis was 8 arbitrary units at 0.04% carbon dioxide, 14 arbitrary units at 0.08% and 15 arbitrary units at 0.12%.
   Calculate the percentage increase in the rate of photosynthesis when the carbon dioxide concentration is raised from 0.04% to 0.08%.3 marks