CAIE A Level Biology 9700 · Photosynthesis
A plant is placed under a light source that emits only far-red light of wavelength 720 nm. It is known that this wavelength is absorbed by photosystem I (PSI) but not by photosystem II (PSII).
Explain the effect of this lighting condition on: (i) cyclic photophosphorylation, (ii) non-cyclic photophosphorylation, (iii) the Calvin cycle.
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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