Biology › Section D · Energy: metabolism, respiration, photosynthesis › Topic D.10

The light-dependent reactions

Plants eat sunlight - but only a thin slice of it, the wavelengths we see as color. The light-dependent reactions convert that light into two carryable currencies, ATP and NADPH: pigments in the thylakoid membrane catch photons, two photosystems boost electrons up an energy staircase, water is split to replace them, and the escaping protons drive an ATP mill that powers sugar assembly in the Calvin cycle.