Noncyclic photophosphorylation (Z scheme) is the process in which the electron expelled by the excited photocentre does not return to it. The lost electron is regained by phololysis of water, which produces O2. It is carried out in collaboration of both photosystems I and II. The two photosystems are connected through an electron transport chain. Both ATP and NADPH + H+ are synthesized by this kind of electron flow.