What happens to the free energy released as electrons are passed from photosystem II to photosystem I through a series of electron carriers?
A) It excites electrons of the reaction center in photosystem I.
B) It is used to establish and maintain a proton gradient.
C) It is used to synthesize ATP through substrate-level phosphorylation.
D) It is used to phosphorylate NAD⁺ to NADPH.

Question

Quizplus · Accepted Answer

The free energy released as electrons are passed through the electron carriers is used to establish and maintain a proton gradient. This proton gradient is essential for the synthesis of ATP through chemiosmosis. Option A is incorrect because photosystem I receives electrons from photosystem II, it does not excite them. Option C is incorrect because substrate-level phosphorylation is not used in photosynthesis. Option D is incorrect because NAD⁺ is not phosphorylated to NADPH, but rather reduced.

What Happens to the Free Energy Released as Electrons Are