Question

The Calvin cycle is considered light-independent because it can occur in darkness. However, most often the Calvin cycle takes place in sunlight.
Which of the following likely explains why?
A) The enzymes involved in the Calvin cycle are unable to bind substrates in the dark.
B) Sunlight is important in activating carbon fixation in the Calvin cycle
C) The Calvin cycle requires ATP and NADPH, which require sunlight to be produced
D) RußP regeneration requires sunlight in order to occur and continue the Calvin cycle.

Answer 1

Answer:

C) The Calvin cycle requires ATP and NADPH, which require sunlight to be produced

Explanation:

The light-dependent phase of photosynthesis includes the photolysis of water molecules. The released electrons are passed to PSII to PSI via electron carriers and finally to NADP+ to reduce it into NADPH.

Transfer of electrons via electron carriers also generates the proton concentration gradient which in turn drives ATP synthesis. ATP and NADPH formed during light reactions are used in the Calvin cycle as an energy source and electron donor respectively.

Hence, to continue, the Calvin cycle requires the synthesis of ATP and NADPH in the presence of light.