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Cytochrome b 6 f and ATP synthase work together to produce ATP (photophosphorylation) in two distinct ways. In non-cyclic photophosphorylation, cytochrome b 6 f uses electrons from PSII and energy from PSI [citation needed] to pump protons from the stroma to the lumen. The resulting proton gradient across the thylakoid membrane creates a proton ...
In the reaction center of PSII of plants and cyanobacteria, the light energy is used to split water into oxygen, protons, and electrons. The protons will be used in proton pumping to fuel the ATP synthase at the end of an electron transport chain. A majority of the reactions occur at the D1 and D2 subunits of PSII.
ATP synthase is the enzyme that makes ATP by chemiosmosis. It allows protons to pass through the membrane and uses the free energy difference to convert phosphorylate adenosine diphosphate (ADP) into ATP. The ATP synthase contains two parts: CF0 (present in thylakoid membrane) and CF1 (protrudes on the outer surface of thylakoid membrane).
The formation of ATP is energetically unfavorable and would not normally proceed. In order to drive this reaction forward, ATP synthase couples ATP synthesis to an electrochemical gradient that drives rotational motor mechanism allowing for ATP production. Because of its rotating subunit, ATP synthase is a molecular machine.
Both the structure of ATP synthase and its underlying gene are remarkably similar in all known forms of life. ATP synthase is powered by a transmembrane electrochemical potential gradient, usually in the form of a proton gradient. In all living organisms, a series of redox reactions is used to produce a transmembrane electrochemical potential ...
F-type proton ATPase [12] [13] (or F-ATPase) typically operates as an ATP synthase that dissipates a proton gradient rather than generating one; i.e. protons flow in the reverse direction compared to V-type ATPases. In eubacteria, F-type ATPases are found in plasma membranes.
In plants, ATP is synthesized in the thylakoid membrane of the chloroplast. The process is called photophosphorylation. The "machinery" is similar to that in mitochondria except that light energy is used to pump protons across a membrane to produce a proton-motive force. ATP synthase then ensues exactly as in oxidative phosphorylation. [28]
Reaction centers are present in all green plants, algae, and many bacteria.A variety in light-harvesting complexes exist across the photosynthetic species. Green plants and algae have two different types of reaction centers that are part of larger supercomplexes known as P700 in Photosystem I and P680 in Photosystem II.