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Cyclic photophosphorylation occurs in both aerobic and anaerobic conditions, driven by the main primary source of energy available to living organisms, which is sunlight. All organisms produce a phosphate compound, ATP , which is the universal energy currency of life.
In cyclic photophosphorylation, cytochrome b 6 f uses electrons and energy from PSI to create more ATP and to stop the production of NADPH. Cyclic phosphorylation is important to create ATP and maintain NADPH in the right proportion for the light-independent reactions. The net-reaction of all light-dependent reactions in oxygenic photosynthesis ...
The cytochrome b 6 f complex is a dimer, with each monomer composed of eight subunits. [3] These consist of four large subunits: a 32 kDa cytochrome f with a c-type cytochrome, a 25 kDa cytochrome b 6 with a low- and high-potential heme group, a 19 kDa Rieske iron-sulfur protein containing a [2Fe-2S] cluster, and a 17 kDa subunit IV; along with four small subunits (3-4 kDa): PetG, PetL, PetM ...
If electrons only pass through once, the process is termed noncyclic photophosphorylation, but if they pass through PSI and the proton pump multiple times it is called cyclic photophosphorylation. When the electron reaches photosystem I, it fills the electron deficit of light-excited reaction-center chlorophyll P700 + of PSI.
Cyclic electron transport or cyclic photophosphorylation produces only ATP. The noncyclic variety involves the participation of both photosystems, while the cyclic electron flow is dependent on only photosystem I. Photosystem I uses light energy to reduce NADP + to NADPH + H +, and is active in both noncyclic and cyclic electron transport. In ...
In non-cyclic photophosphorylation, ferredoxin is the last electron acceptor thus reducing the enzyme NADP + reductase. It accepts electrons produced from sunlight - excited chlorophyll and transfers them to the enzyme ferredoxin: NADP + oxidoreductase EC 1.18.1.2 .
English: A diagram of cyclic phosphorylation (also referred to as cyclic electron flow or cyclic electron transport). It displays light reactions in the thylakoid membrane, with parts of the cycle highlighted. Cyclic phosphorylation occurs only in photosystem I and produces ATP, but not NADPH. Created using Inkscape.
The proton gradient can be generated through either noncyclic or cyclic photophosphorylation. Of the proteins that participate in noncyclic photophosphorylation, photosystem II (PSII), plastiquinone, and cytochrome b 6 f complex directly contribute to generating the proton gradient. For each four photons absorbed by PSII, eight protons are ...