Where do the light-dependent reactions occur?

Where do the light-dependent reactions occur?

• A. Stroma
• B. Nucleus
• C. Thylakoid membranes
• D. Cytoplasm

Answer: (C)

Light-dependent reactions occur in the thylakoid membranes inside chloroplasts. These membranes host the photosystems, the electron transport chain, and ATP synthase, all working together to convert light energy into chemical energy. When light is absorbed by chlorophyll, electrons are excited and travel through the electron transport chain, pumping protons into the thylakoid lumen and driving ATP formation. Water is split at photosystem II, releasing oxygen and providing electrons. The excited electrons ultimately reduce NADP+ to NADPH, supplying reducing power for the later stages of photosynthesis. The stroma, not the thylakoid membranes, is where the Calvin cycle uses ATP and NADPH to synthesize sugars, while the nucleus and cytoplasm are not the sites of these light-driven reactions.

Light-dependent reactions occur in the thylakoid membranes inside chloroplasts. These membranes host the photosystems, the electron transport chain, and ATP synthase, all working together to convert light energy into chemical energy. When light is absorbed by chlorophyll, electrons are excited and travel through the electron transport chain, pumping protons into the thylakoid lumen and driving ATP formation. Water is split at photosystem II, releasing oxygen and providing electrons. The excited electrons ultimately reduce NADP+ to NADPH, supplying reducing power for the later stages of photosynthesis. The stroma, not the thylakoid membranes, is where the Calvin cycle uses ATP and NADPH to synthesize sugars, while the nucleus and cytoplasm are not the sites of these light-driven reactions.