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The transfer of electrons from a donor molecule to an acceptor molecule can be spatially separated into a series of intermediate redox reactions. This is an electron transport chain (ETC). Electron transport chains often produce energy in the form of a transmembrane electrochemical potential gradient.
The electrons are transferred to plastoquinone and two protons, generating plastoquinol, which released into the membrane as a mobile electron carrier. This is the second core process in photosynthesis. The initial stages occur within picoseconds, with an efficiency of 100%. The seemingly impossible efficiency is due to the precise positioning ...
Electron transfer (ET) occurs when an electron relocates from an atom, ion, or molecule, to another such chemical entity. ET describes the mechanism by which electrons are transferred in redox reactions. [2] Electrochemical processes are ET reactions. ET reactions are relevant to photosynthesis and respiration and commonly involve transition ...
This process of reducing quinone is comparable to that which takes place in the bacterial reaction center. Photosystem II obtains electrons by oxidizing water in a process called photolysis. Molecular oxygen is a byproduct of this process, and it is this reaction that supplies the atmosphere with oxygen.
Light-dependent reactions of photosynthesis at the thylakoid membrane. Photosystems are functional and structural units of protein complexes involved in photosynthesis. Together they carry out the primary photochemistry of photosynthesis: the absorption of light and the transfer of energy and electrons.
Ferredoxin: NADP + reductase is the last enzyme in the transfer of electrons during photosynthesis from photosystem I to NADPH. [2] The NADPH is then used as a reducing equivalent in the reactions of the Calvin cycle. [2] Electron cycling from ferredoxin to NADPH only occurs in the light in part because FNR activity is inhibited in the dark. [11]
The excited electrons lost from the reaction center of photosystem I are replaced by transfer from plastocyanin, whose electrons come from electron transport through photosystem II. Photosystem II, as the first step of the Z-scheme , requires an external source of electrons to reduce its oxidized chlorophyll a reaction center.
Photosystem I [1] is an integral membrane protein complex that uses light energy to catalyze the transfer of electrons across the thylakoid membrane from plastocyanin to ferredoxin. Ultimately, the electrons that are transferred by Photosystem I are used to produce the moderate-energy hydrogen carrier NADPH . [ 2 ]