CAIE A Level Biology 9700 · Photosynthesis
A scientist incubated isolated chloroplasts with 14C-labeled carbon dioxide (14CO2) in the light. After a brief exposure, the first organic compound containing 14C was identified as 3-phosphoglycerate (GP). After a longer incubation, 14C appeared in triose phosphate (TP). Explain the sequence of reactions in the Calvin cycle that accounts for these observations. In your answer, refer to the roles of rubisco, ATP, reduced NADP, and the need to regenerate RuBP.
6 marks, so the mark scheme is looking for about 6 separate creditworthy points. Making the same point twice in different words earns it once.
Explain means: Give the reasons or the mechanism: why or how something happens. Link each point to the next with because, so or which means. A list of facts with no links usually loses the reasoning marks.
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