chemiosmotic theory
A proposed mechanism of oxidative phosphorylation in the mitochondrion and chloroplast that requires (1) electron transport to be arranged across the mitochondrial or chloroplast membrane so that protons are vectorially transported to its outer surface, (2) ATP synthesis to be arranged in the membrane so that the proton gradient can be used to drive ATP synthesis, and (3) that the mitochondrial/chloroplast membrane is impermeable to protons and defines an osmotically isolated space. The electron transport chain is composed alternately of hydrogen atom carriers and electron carriers, so that transfer from the former to the latter permits liberation of protons and their vectorial transport across the mitochondrial or chloroplast membrane. Because proton transport is not accompanied by an equivalent transport of electrons across the membrane, it generates not only a chemical potential (pH) but also an electron potential (), and the two together are termed the proton motive force. (see also chemical coupling hypothesis; conformational hypothesis; electrochemical gradient; P:O ratio; proton motive force)
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