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reaction centre has highest peak at 700nm, hence called P700. And PS II reaction, centre has highest peak at 680 nm, so called P680., , The Electron Transport System, , e Reaction centre of photosystem II absorbs light of 680 nm in red region and causing, electron to become excited. These electrons are picked by an electron acceptor which, passes to electron transport system consisting of cytochromes., , Photosystem II Photosystem 1, , , , a;, H20—> 2e°+ 2H* + [0], , e Electrons are passed down the electron transport chain and then to the pigment of PS, lL, , e Electron in the PSI also get excited due to light of wavelength 700nm and are, transferred to another accepter molecule having a greater redox potential., , e When electron passes in downhill direction, energy is released. This is used to reduce, the ADP to ATP and NADP+ to NADPH. The whole scheme of transfer of electron is, , 4/10, Material Downloaded From SUPERCOP, , called Z-scheme due to its shape., e Photolysis of water release electrons that provide electron to PS II. Oxygen is also, released during this process., , 2H2O > 4H* + Op, + 4e, ¢ Difference between cyclic and non-cyclic photophosphorylation, , Cyclic photophosphorylation Non-cyclic photophosphorylation, , . Itis performed by photosystem I, , . It is performed by collaboration of both PS, , , , , , independently., land PS II., . An external source of electron is not ., . . The process requires an external electron, required., . donor., . It synthesizes only ATP. ., . . 3. It synthesizes ATP and NADH both., . It occurs only in stromal or intergranal . ., . . It occurs in the granal thylakoids only., thylakoids., Photosystem Il Photosystem I, Photosystem I ——— ——, , NADP*, , Coecenara + NADPH, , , , , , ox, H2O0—> 2e"+ 2H* + [O}, Chemiosmotic Hypothesis of ATP FORMATION, , This hypothesis was proposed by Mitchell in 1961. ATP synthesis is linked to development of, proton gradient across the membrane of thylakoid and mitochondria., , The process that causes development of proton gradient across the membrane is