Question

Answer the following:
(1) Which photosystem is operational during cyclic photophosphoryl
(ii) Which organisms show cyclic photophosphorylation ? plan
() How does Peso regain its lost electrons ?
(iv) Which reaction centre brings about splitting of water ? Dhe

Answer 1

• Cyclic photophosphorylation can be defined as the synthesis of ATP coupled to electron transport activated by Photosystem I solely, and can therefore proceed in long-wave-length light (03BB 2265 700 nm). This proces is unaffected by the specific inhibitors of Photosystem II, such as CMU, DCMU and orthophenanthroline.
• In bacterial photosynthesis, a single photosystem is used, and therefore is involved in cyclic photophosphorylation. It is favored in anaerobic conditions and conditions of high irradiance and CO2 compensation points.
• Photosystem II: During the light reactions of photosynthesis, photosystem II reaction centre P 680 absorbs light to boost its electrons and attains oxidized state. To reduce the oxidized chlorophyll molecules or to regain the lost electrons, the source of electrons is water in green plants and cyanobacteria.Water splitting The oxidation of water to molecular oxygen requires extraction of four electrons and four protons from two molecules of water.