CBSE Class 10 Answered

Photophosphorylation is the process of creating ATP using a proton gradient created by the energy gathered from sunlight. Since formation of this proton gradient is light-dependent, the process is called photophosphorylation.

Noncyclic Photophosphorylation refers to the ATP generated by protons moved across the thylakoid membranes during the Z-scheme. The Cytb6-f complex acts as an electron transport chain. As the electrons lose energy (during a series of re/dox reactions), protons are moved into the thylakoid space. This proton gradient can be used to generate ATP chemiosmotically.

During cyclic photophosphorylation the electrons are recycled, hence the name cyclic photophosphorylation. The excited electrons resulting from the absorption of light in photosystem I are received by the primary electron acceptor and then transferred to the cytb6-f complex which acts as an electron transport chain. The electrons return back to the reaction center of Photosystem I, where the cycle is ready to start all over. The electrons are using to translocate Protons which the ATPase uses to synthesize ATP. No reduction of NADP+ occurs in Cyclic Photophosphorylation.