Which stage of photosynthesis captures light energy to synthesize ATP and NADPH?

• A. Light-dependent reactions
• B. Calvin cycle
• C. Dark reactions
• D. Glycolysis

Answer: (A)

Light energy is captured in the light-dependent reactions. In this stage, photons energize chlorophyll in the photosystems, driving electrons through an electron transport chain in the thylakoid membranes. As this happens, a proton gradient is built up and ATP synthase uses it to produce ATP. The energized electrons are also transferred to NADP+, forming NADPH, which provides reducing power for the next stage. Water is split to replace the electrons, releasing oxygen as a by-product. The ATP and NADPH generated here are then used by the Calvin cycle to synthesize sugars from CO2. The Calvin cycle itself uses these products rather than capturing light energy, and glycolysis is a separate pathway in respiration, not photosynthesis.