The light-independent reaction (Calvin cycle)AQA A-Level Biology: Mind map

Exam questions on The light-independent reaction (Calvin cycle)

1. A plant biochemist is studying the first step of the Calvin cycle in an extract of chloroplasts, using carbon dioxide and the five-carbon compound ribulose bisphosphate (RuBP).
   Explain, using the number of carbon atoms in each compound, how one carbon dioxide molecule reacting with RuBP leads to the formation of two molecules of GP.2 marks
2. A culture of algae is kept in bright light with a constant supply of carbon dioxide. The concentrations of glycerate 3-phosphate (GP), reduced NADP and ribulose bisphosphate (RuBP) in the cells are steady. The carbon dioxide supply is then suddenly stopped while the light stays on.
   Explain the change in the concentration of RuBP after the carbon dioxide supply is stopped.2 marks
3. A herbicide that inhibits the enzyme catalysing the reduction of glycerate 3-phosphate (GP) to triose phosphate (TP) is sprayed on a field of wheat in bright sunlight.
   Predict and explain the effect of the herbicide on the concentrations of GP, triose phosphate and RuBP in the wheat leaves.3 marks