?

Biochemistry

Free Version

Upgrade subject to access all content

Easy

Photosynthesis: Cyclic vs. Noncyclic Electron Transport

BIOCHM-8@GWIY

During photosynthesis, when the absorption of light energy exceeds the capacity of the biochemical reactions of ${ CO }_{ 2 }$ fixation in land plants, noncyclic electron transport likely stops and cyclic electron transport around photosystem I (PSI), e.g., from ferredoxin (Fd) to plastoquinone (PQ), predominates.

Which of the following would be observed under these conditions?

A

ATP synthesis slows and NADPH synthesis increases.

B

Both ATP and NADPH synthesis stop.

C

ATP synthesis stops and NADPH synthesis continues.

D

ATP synthesis continues and NADPH synthesis stops.

E

No change is observed in either ATP or NADPH synthesis.

F

Oxygen evolution increases.

G

Pumping of protons into the thylakoid lumen stops and the stromal pH decreases.