Principles Of Biology (POB) Exam 2 Practice

In the light reactions, NADP+ is reduced to which molecule?

NADH NADPH NADP+ NAD+

Correct Answer:

NADPH

Explanation:

NADP+ serves as the final electron acceptor in the light reactions of photosynthesis, so it gets reduced to NADPH. As electrons move from water through the photosynthetic electron transport chain (PSII → plastoquinone → cytochrome b6f → plastocyanin → PSI) they end up on ferredoxin, and ferredoxin-NADP+ reductase transfers those electrons to NADP+, along with a proton, forming NADPH. This NADPH carries reducing power to the Calvin cycle to help convert CO2 into sugars. NADH is a product of respiration and is not the carrier produced by the light reactions, and NAD+ is the oxidized form, not the reduced carrier used here. The phosphate-containing NADP+ is specifically reduced to NADPH, which is why NADPH is the correct product.

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