photophosphorylation

Photophosphorylation is the process by which light energy is used to synthesize ATP (adenosine triphosphate) from ADP (adenosine diphosphate) and phosphate. This occurs during the light-dependent reactions of photosynthesis within the chloroplasts of plant cells.12

Sunlight absorbed by pigments like chlorophyll excites electrons, which then travel through an electron transport chain. This flow generates a proton gradient across the thylakoid membranes. The potential energy stored in this gradient is used by an enzyme complex to convert ADP and phosphate into ATP, the cell's primary energy currency. This process is distinct from oxidative phosphorylation, which occurs in mitochondria. Water molecules are split to replace electrons, releasing oxygen as a byproduct.342