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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 parts: a reaction center, where the photochemistry occurs, and an antenna complex, which surrounds the reaction center. The antenna complex contains hundreds of chlorophyll molecules which funnel the excitation energy to the center of the photosystem. At the reaction center, the energy will be trapped and transferred to ...
In a transmitter, the antenna feed is considered to be all components between the transmitter's final amplifier and the antenna's feedpoint. [3] In a receiver, it is all components between the antenna and the receiver's input terminals. In some cases such as parabolic dishes it is also defined to include the feed antenna or feed horn.
Cytochrome b is a protein found in the membranes of aerobic cells. In eukaryotic mitochondria (inner membrane) and in aerobic prokaryotes, cytochrome b is a component of respiratory chain complex III (EC 1.10.2.2) — also known as the bc1 complex or ubiquinol-cytochrome c reductase.
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.
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: