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Photosystem I (PSI, or plastocyanin–ferredoxin oxidoreductase) is one of two photosystems in the photosynthetic light reactions of algae, plants, and cyanobacteria. 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 ...
The cyclic light-dependent reactions occur only when the sole photosystem being used is photosystem I. Photosystem I excites electrons which then cycle from the transport protein, ferredoxin (Fd), to the cytochrome complex, b 6 f, to another transport protein, plastocyanin (Pc), and back to photosystem I. A proton gradient is created across the ...
Studies have actually demonstrated that the two wavelengths together have a synergistic effect on the photosynthetic activity, rather than an additive one. [ 1 ] Each photosystem has two parts: a reaction center, where the photochemistry occurs, and an antenna complex , which surrounds the reaction center.
Unlike non-cyclic photophosphorylation, NADP + does not accept the electrons; they are instead sent back to the cytochrome b 6 f complex. [citation needed] In bacterial photosynthesis, a single photosystem is used, and therefore is involved in cyclic photophosphorylation.
Photosystem II is present on the thylakoid membranes inside chloroplasts, the site of photosynthesis in green plants. [9] The structure of Photosystem II is remarkably similar to the bacterial reaction center, and it is theorized that they share a common ancestor. The core of Photosystem II consists of two subunits referred to as D1 and D2 ...
They are transmembrane proteins embedded in the chloroplast thylakoid or bacterial cell membrane. Plants, algae, and cyanobacteria have one type of PRC for each of its two photosystems. Non-oxygenic bacteria, on the other hand, have an RC resembling either the Photosystem I centre (Type I) or the Photosystem II centre (Type II).
Using this cyclic electron chain around photosystem one (PS I), chlororespiration compensates for the lack of light. This cyclic pathway also allows electrons to re-enter the PQ pool through NAD(P)H enzyme activity and production, which is then used to supply ATP molecules (energy) to plant cells.
In photosynthesis, plastocyanin functions as an electron transfer agent between cytochrome f of the cytochrome b 6 f complex from photosystem II and P700+ from photosystem I. Cytochrome b 6 f complex and P700 + are both membrane-bound proteins with exposed residues on the lumen-side of the thylakoid membrane of chloroplasts. Cytochrome f acts ...