respiratory chain
Oxford Dictionary of Biochemistry:
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respiratory chain
or electron-transport chain
the sequence of enzymes and other proteins within the mitochondrion and prokaryotic cell membranes by which instrates, including NADH and succinate, are oxidized by dioxygen. It is fundamental to tissue respiration (def. 2) which has the function of maintaining tissue metabolism through oxidative phosphorylation. The chain can be separated into a number of particles (see respiratory complex) each of which contains individual elements of the chain. The mechanism involves, in the case of NADH, removal by NADH dehydrogenase of a proton plus two electrons. In the case of succinate, there is a transfer of two hydride ions (i.e. two protons plus two electrons) by succinate dehydrogenase to ubiquinone; other flavoproteins can similarly oxidize fatty acyl-CoA or β -hydroxybutyrate or α -glycerophosphate. The protons are initially released to the intermembrane space, and the electrons are transferred by the appropriate flavoprotein to ubiquinone, from which they are transferred singly in sequence to cytochrome b, cytochrome c 1, cytochrome c, and cytochrome a /a 3 at which point they reduce molecular oxygen to promote formation of water with the protons that were formed earlier. Many other components are also involved. In tightly coupled mitochondria, the protons released to the intermembrane space reach the mitochondrial matrix (the space in which they react with molecular oxygen) by transfer through the inner mitochondrial membrane by the F0 F1 complex of the mitochondrial ATPase (see H+ -transporting ATP synthase), with concomitant phosphorylation of ADP to ATP. See also chemiosmotic coupling hypothesis.
the sequence of enzymes and other proteins within the mitochondrion and prokaryotic cell membranes by which instrates, including NADH and succinate, are oxidized by dioxygen. It is fundamental to tissue respiration (def. 2) which has the function of maintaining tissue metabolism through oxidative phosphorylation. The chain can be separated into a number of particles (see respiratory complex) each of which contains individual elements of the chain. The mechanism involves, in the case of NADH, removal by NADH dehydrogenase of a proton plus two electrons. In the case of succinate, there is a transfer of two hydride ions (i.e. two protons plus two electrons) by succinate dehydrogenase to ubiquinone; other flavoproteins can similarly oxidize fatty acyl-CoA or β -hydroxybutyrate or α -glycerophosphate. The protons are initially released to the intermembrane space, and the electrons are transferred by the appropriate flavoprotein to ubiquinone, from which they are transferred singly in sequence to cytochrome b, cytochrome c 1, cytochrome c, and cytochrome a /a 3 at which point they reduce molecular oxygen to promote formation of water with the protons that were formed earlier. Many other components are also involved. In tightly coupled mitochondria, the protons released to the intermembrane space reach the mitochondrial matrix (the space in which they react with molecular oxygen) by transfer through the inner mitochondrial membrane by the F0 F1 complex of the mitochondrial ATPase (see H+ -transporting ATP synthase), with concomitant phosphorylation of ADP to ATP. See also chemiosmotic coupling hypothesis.
| respiratory burst, respiration, resorcinol | |
| respiratory complex, respiratory control, respiratory pigment |
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Oxford Dictionary of Biochemistry
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