Cyclic photophosphorylationNon-cyclic photophosphorylation 1- It occurs in photosystem I. 1- It occurs in both photosystem I and photosystem II. 2- Only Atp is produced 2- Both ATP and NADPH are produced. 3- Electrons expelled by photosystem and return back. 3- Electrons expelled by photosystem but do not return back. 4- Photolysis of water does not occur. 4- Photolysis of water occur. 5- Oxygen is not released. 5- Oxygen is released. 6- Water is not consumed. 6- Water is consumed.