electron transport chain
electron transport chain (electron transport system) A sequence of biochemical reduction–oxidation reactions that effects the transfer of electrons through a series of carriers. An electron transport chain, also known as the respiratory chain, forms the final stage of aerobic respiration. In the mitochondria, NADH or FADH2, generated by the Krebs cycle, transfer their electrons through a chain of carrier molecules, including ubiquinone and a series of cytochromes, that undergo reversible reduction–oxidation reactions, accepting electrons and then donating them to the next carrier in the chain – a process known as electron flow. Cytochrome oxidase combines electrons and hydrogen ions with oxygen to form water (see illustration). This process is coupled to the formation of ATP (see chemiosmotic theory; oxidative phosphorylation). An electron transport chain also occurs in the thylakoid membranes of chloroplasts in photosynthesis; the carrier molecules include plastoquinone, plastocyanin, and ferredoxin. See photophosphorylation.
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Cytochrome , Cytochromes are electron-transporting protein pigments concerned with cell respiration that contain an iron-containing molecule called heme, allied t… Atp Synthesis , chemiosmotic theory A theory postulated by the British biochemist Peter Mitchell (1920–92) to explain the formation of ATP in the mitochondrial elect… Photophosphorylation , photophosphorylation The formation of ATP from ADP and inorganic phosphate using light energy in photosynthesis (compare oxidative phosphorylation).… Scanning electron microscopes , SEM See SCANNING ELECTRON MICROSCOPE.
sem. semester
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• seminary Cytochrome oxidase , cytochrome oxidase An enzyme containing both copper and iron that, because of its ability (unique among the cytochromes) to reduce molecular oxygen t… Scanning Electron Microscope , scanning electron microscope (SEM) A microscope that operates by scanning a finely focused beam of electrons across the specimen. The reflected elect…
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electron transport chain