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Plastoquinone (PQ) is a terpenoid-quinone (meroterpenoid) molecule involved in the electron transport chain in the light-dependent reactions of photosynthesis. The most common form of plastoquinone, known as PQ-A or PQ-9, is a 2,3-dimethyl-1,4- benzoquinone molecule with a side chain of nine isoprenyl units.
The light-harvesting complex (or antenna complex; LH or LHC) is an array of protein and chlorophyll molecules embedded in the thylakoid membrane of plants and cyanobacteria, which transfer light energy to one chlorophyll a molecule at the reaction center of a photosystem. The antenna pigments are predominantly chlorophyll b, xanthophylls, and ...
The first reaction of Q cycle is the 2-electron oxidation of ubiquinol by two oxidants, c 1 (Fe 3+) and ubiquinone: CoQH 2 + cytochrome c 1 (Fe 3+) + CoQ' → CoQ + CoQ' −• + cytochrome c 1 (Fe 2+) + 2 H + (intermembrane) The second reaction of the cycle involves the 2-electron oxidation of a second ubiquinol by two oxidants, a fresh c 1 ...
Each photosystem has two main subunits: an antenna complex (a light harvesting complex or LHC) and a reaction center. The antenna complex is where light is captured, while the reaction center is where this light energy is transformed into chemical energy. At the reaction center, there are many polypeptides that are surrounded by pigment proteins.
Each antenna is alternately connected to a transmitter having a particular source impedance, and a receiver having the same input impedance (the impedance may differ between the two antennas). It is assumed that the two antennas are sufficiently far apart that the properties of the transmitting antenna are not affected by the load placed upon ...
However, if a different frequency is sent into the feeds, they will arrive at the ends at different times, the phase relationship will not be maintained, [3] and squint will result. Frequency-dependant phase shifting of the elements of the array can be used to compensate for the squint, [4] which leads to the concept of a squintless antenna or ...
Cytochrome c 1 transfers its electron to cytochrome c (not to be confused with cytochrome c1), and the B H Heme transfers its electron to a nearby ubiquinone, resulting in the formation of a ubisemiquinone. Cytochrome c diffuses. The first ubiquinol (now oxidised to ubiquinone) is released, whilst the semiquinone remains bound. Round 2:
The difference between Photosystem II and the bacterial reaction center is the source of the electron that neutralizes the pair of chlorophyll a molecules. In the bacterial reaction center, the electron is obtained from a reduced compound haem group in a cytochrome subunit or from a water-soluble cytochrome-c protein.