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In cyclic photophosphorylation, the high-energy electron released from P700, a pigment in a complex called photosystem I, flows in a cyclic pathway. The electron starts in photosystem I, passes from the primary electron acceptor to ferredoxin and then to plastoquinone , next to cytochrome b 6 f (a similar complex to that found in mitochondria ...
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.
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 ...
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.
Simplified diagram of photophosphorylation. PSII also relies on light to drive the formation of proton gradients in chloroplasts, however, PSII utilizes vectorial redox chemistry to achieve this goal. Rather than physically transporting protons through the protein, reactions requiring the binding of protons will occur on the extracellular side ...
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 ...
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 ...
The experimental evidence that oxygen is released through cyclic reaction of oxygen evolving complex (OEC) within one PSII was provided by Pierre Joliot et al. [18] They have shown that, if dark-adapted photosynthetic material (higher plants, algae, and cyanobacteria) is exposed to a series of single turnover flashes, oxygen evolution is ...