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Plants, algae, cyanobacteria

Photosynthesis – Light Reactions

Capture of light energy to produce ATP and NADPH, with O₂ as a byproduct.

Overview

The light-dependent reactions of photosynthesis occur in the thylakoid membranes of chloroplasts. Photosystems I and II absorb photons, driving electron transport that generates a proton gradient for ATP synthesis (photophosphorylation) and reduces NADP⁺ to NADPH. Water is split by Photosystem II, releasing O₂.

Cellular Location

Thylakoid membrane (chloroplast)

Clinical Significance

Foundation of nearly all food webs; responsible for atmospheric oxygen; key target for improving crop yields.

Key Molecules

Key Enzymes

Related Pathways