Photosynthesis (light-dependent reactions)

What is photosynthesis (light-dependent reactions)?

The light-dependent reactions of photosynthesis happen in the thylakoid membranes of chloroplasts. Light excites electrons in chlorophyll, driving an electron transport chain that pumps H⁺ into the thylakoid lumen. The H⁺ gradient drives ATP synthase (photophosphorylation). Water is split (photolysis) to replace lost electrons, producing O₂. NADP is reduced to NADPH. ATP and NADPH then power the Calvin cycle in the stroma.