As electrons are passed through the system of electron carriers associated with photosystem ii, they lose energy. what happens to this energy?

a) it excites electrons of the reaction center of photosystem i.
b) it is lost as heat.
c) it is used to establish and maintain a proton gradient.
d) it is used to phosphorylate nad+ to nadph, the molecule that accepts electrons from photosystem i.

Option C) It is used to establish and maintain a proton gradient

Explanation:

Once light photons excite photosystem II, electrons of the main central chlorophyl  are ejected to reach another energy level.  One different molecule accepts those electrons, and they are delivered to a redox chain (also called respiratory chain). Passing across this chain, protons are pumped to the other side of the membrane of chloroplasts, or equivalent, and a proton gradient is produced.  This gradient will allow ATP production. This is energy to be used in the Calvin cycle.

Finally those electrons will arrive to the photosystem I, where Option D occurs, that is NAD+ will be phosphorylated to NADPH, that represents reducing power for the Calvin cycle

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