Photophosphorylation is the synthesis of ATP during photosynthesis. It is of two types: (i) Cyclic photophosphorylation: In cyclic photophosphorylation only ATP is produced. It starts with P700 which being excited releases electrons that are accepted by ferredoxine. The electrons passess through plastoquinone, cyt. −b6 , cyt.-f and plastocyanin to P700 . The energy released between cyt. −b6 and cyt.-f is used to form ATP. (ii) Non-cyclic photophosphorylation: In non-cyclic photophosphorylation electron released from P680 goes through PS-I and PS-II to NADP+ , i.e., ATP and NADPH2 are formed in non-cyclic photophosphorylation. O2 is released in PS-II by photolysis of water.