In photosynthesis, what is the role of NADP-?

• A. Absorb light energy
• B. Trap and transfer electrons and hydrogen ions
• C. Pumps protons across a membrane
• D. Store energy as ATP

Answer: (B)

NADP+ acts as the carrier that traps electrons and a hydrogen ion, becoming NADPH. In the light-dependent reactions, light energy drives electrons through the electron transport chain to photosystem I. At the end of this chain, electrons are transferred to NADP+, with a proton added to form NADPH. This NADPH carries high-energy electrons to the Calvin cycle, supplying the reducing power needed to convert carbon dioxide into sugars.

Other options don’t fit because absorbing light energy is done by pigments like chlorophyll, proton pumping across a membrane is the role of the electron transport chain complexes that build the proton gradient, and storing energy as ATP is the job of ATP synthase using that gradient. NADPH, not ATP, provides the reducing equivalents for carbon fixation.