Photosynthesis Light Reactions 3

Question 1

Which component of the thylakoid membrane directly uses the proton gradient to synthesize ATP?

Accepted Answer

ATP synthase (CF1-CF0)

Answer

The chloroplast ATP synthase (CF1-CF0 complex) uses the proton-motive force created by the proton gradient across the thylakoid membrane to drive ATP synthesis.

Question 2

What is the significance of the high proton concentration in the thylakoid lumen?

Accepted Answer

It creates a proton-motive force that drives ATP synthesis

Answer

The accumulation of protons in the thylakoid lumen creates a electrochemical gradient (proton-motive force) that powers ATP synthase to produce ATP.

Question 3

Which electron carrier in the light reactions is embedded in the thylakoid membrane and carries both electrons and protons?

Accepted Answer

Plastoquinone

Answer

Plastoquinone (PQ) is a lipid-soluble molecule embedded in the thylakoid membrane that picks up electrons and protons from PSII and delivers them to the cytochrome b6f complex.

Question 4

At which absorption wavelength does Photosystem I show maximum efficiency?

Accepted Answer

700 nm

Answer

Photosystem I has its reaction center chlorophyll a (P700) with an absorption maximum at 700 nm, hence its designation.

Question 5

What happens to the electrons that are used to reduce NADP+ in the light reactions?

Accepted Answer

They are permanently incorporated into NADPH

Answer

The electrons transferred to NADP+ remain in NADPH, which then carries them to the Calvin cycle where they are used in the reduction of 3-PGA.

Photosynthesis Practice Test

Photosynthesis Practice Test

Photosynthesis Light Reactions 3