Photophosphorylation

Photophosphorylation is the process of phosphorylation of ADP to form ATP using the energy from photons (e.g. from sunlight) in photosynthesis. There are two types: cyclic photophosphorylation and non-cyclic photophosphorylation.

In photophosphorylation, light energy is used to pump protons across a biological membrane, mediated by flow of electrons through an electron transport chain, storing potential energy in a proton gradient. The protons return across the membrane though an enzyme called ATP synthase which synthesises ATP from ADP and inorganic phosphate. ATP is essential in the Calvin cycle to supply energy for the synthesis of carbohydrates from carbon dioxide and NADPH.