If a plant has plenty of NADPH available but is running low on ATP, how does the plant make up the ATP deficit during the daylight hours?
A) It uses photorespiration.
B) It uses noncyclic photophosphorylation.
C) It uses cyclic photophosphorylation.
D) It decreases the rate of chemiosmosis.
E) It increases the rate of the Calvin cycle.

Question

Quizplus · Accepted Answer

Cyclic photophosphorylation can be used by plants to generate additional ATP when they have plenty of NADPH but are running low on ATP. In cyclic photophosphorylation, electrons are cycled back through Photosystem I instead of being passed to NADP+ and instead generate additional ATP. This process does not produce additional reducing equivalents (NADPH) and therefore can be beneficial when an excess of reducing equivalents are already present.

If a Plant Has Plenty of NADPH Available but Is