Chemiosmosis - in Plants

In Plants

The light reactions of photosynthesis generate energy by chemiosmosis. Light energy (photons) are received by the antenna complex of Photosystem 2, which excites a pair of electrons to a higher energy level. These electrons travel down an electron transport chain, causing H+ to diffuse across the thylakoid membrane into the inter-thylakoid space. These H+ are then transported down their concentration gradient through an enzyme called ATP-synthase, creating ATP by phosphorylation of ADP to ATP. The electrons from the initial light reaction reach Photosystem 1, then are raised to a higher energy level by light energy and then received by an electron receptor and reduce NADP+ to NADPH+H. The electrons from Photosystem 2 get replaced by the splitting of water, called "photolysis." Two water molecules must be split in order to gain 4 electrons (as well as O2, the oxygen eudicots require for survival).