(photosynthetic phosphorylation) The production of ATP from ADP and inorganic phosphate utilizing light-induced photosynthetic electron transport as a source of energy. Two types of photophosphorylation occur, noncyclic and cyclic. In noncyclic photophosphorylation electrons are passed from water to NADP + via * photosystems I and II . During the transfer of electrons from the primary electron acceptor of photosystem II (termed C550) to P700 through plastoquinone, plastocyanin, and various cytochromes, one molecule of ATP is formed. In cyclic photophosphorylation only photosystem I is involved. Energy absorbed by P700 releases electrons, which are absorbed by a primary acceptor termed P430. Electrons then pass, via cytochrome b 6, into the chain connecting the primary electron acceptor of photosystem II to photosystem I. A molecule of ATP is formed as the electron passes down to P700. Cyclic phosphorylation does not produce reduced NADP +. |
