The process by which ATP formation occurs inside the cell is known as phosphorylation. When this ATP synthesis occurs from the ADP in the presence of light, this process is known as the photophosphorylation. If the photophosphorylation involves both the PS I and PS II reaction centers in a non-cyclic pattern this process is known as non-cyclic photophosphorylation. In the non-cyclic photophosphorylation both the photosystems are linked by the electron transport chain. As a result of this Z scheme ATP and NADPH+H+ and oxygen are obtained.