Oxidative Chemiosmotic coupling

Mitchell, P. (1966). Chemiosmotic Coupling in Oxidative and Photosynthetic Phosphorylation. Glynn Research, Bodmin, Cornwall, U.K. 

ATP formation coupled to electron flow in mitochondria is usually called oxidative phosphorylation. Because electron flow involves both reduction and oxidation, more appropriate names are respiratory phosphorylation and respiratory-chain phosphorylation, terminology that is also more consistent with photophosphorylation for ATP formation in photosynthesis. As with photophosphorylation, the mechanism of oxidative phosphorylation is not yet fully understood in molecular terms. Processes like phosphorylation accompanying electron flow are intimately connected with membrane structure, so they are much more difficult to study than are the biochemical reactions taking place in solution. A chemiosmotic coupling mechanism between electron flow and ATP formation in mitochondria is generally accepted, and we will discuss some of its characteristics next. 

Fig. 1.3. A scheme of oxidative phosphorylation according to the chemiosmotic coupling hypothesis.

The inconsistency between experiment and prediction must lead to the rejection of the model used to describe the system. In the case of oxidative phosphorylation this has led to a refined model, in which the chemiosmotic coupling is visualized as taking place within units of one (or a few) respiratory chain(s) plus ATP synthase, while the pumped protons have only limited access to the bulk phase inside and/or outside the mitochondrion [42]. This more refined model can again be tested by deriving from it flux-force relations according to the MNET approach. A discussion of the refined model can be found in Ref. 43. 

Nicholls, D.G., Cannon, B., Grav, H.J. and Lindberg, O. (1974) In Dynamics of Energy-Transducing Membranes (Emster, L., Estabrook, R.W. and Slater, E.C., eds.) pp. 529-537, Elsevier, Amsterdam. Mitchell, P. (1966) Chemiosmotic Coupling in Oxidative and Photosynthetic Phosphorylation. Glynn Res. Ltd., Bodmin, Cornwall, England. 

The anisotropic organization of electron carriers across the membrane accounts for the vectorial transport of protons from the inside to the outside of the membrane, which occurs with the passage of electrons. The coupling of this proton gradient to a proton-translocating ATP synthase (also known as ATP synthetase) accounts for the chemiosmotic coupling in oxidative phosphorylation. 

Mitchell, P., Chemiosmotic coupling in oxidative and photosynthetic phosphorylation, Biol. Rev. Camb. Philos. Soc., 1966, 41, 445-502. WiKSTEOM, M.K., Proton pump coupled to cytochrome c oxidase in mitochondria. Nature, 1977, 266, 271-273. 

See also Electron Transport, P/O Ratio, Chemiosmotic Coupling, Integrity of Mitochondrial Membranes, Uncoupling ETS and Oxidative Phosphorylation, The FIFO Complex, Oxidation as a Metabolic Energy Source (from Chapter 12)... 

In 1961, Peter Mitchell proposed the now widely accepted chemiosmotic coupling hypothesis to explain ATP synthesis as a result of electron transport (ETS) and oxidative phosphorylation. It consists of the following principles ... 

See also Chemiosmotic Coupling, Oxidative Phosphorylation, Uncoupling ETS and Oxidative Phosphorylation, Respiratory Control... 

Mechanism of Oxidative Phosphorylation Chemiosmotic Coupling (Figure 15.15)... 

Chemiosmotic coupling is the mechanism most widely used to explain the manner in which electron transport and oxidative phosphorylation are coupled to one another. In this mechanism, the proton gradient is directly linked to the phosphorylation process. The way in which the proton gradient leads to the production of ATP depends on ion channels through the inner mitochondrial membrane these channels are a feature of the structure of ATP synthase. Protons flow back into the matrix through proton channels in the Fq part of the ATP synthase. The flow of protons is accompanied by formation of ATP, which occurs in the Fj unit. 

Fillingame, R. The Proton-Translocating Pumps of Oxidative Phosphorylation. Ann. Rev. Biochem. 49, 1079-1114 (1980). [A review of chemiosmotic coupling.]... 

Figure 1. Chemiosmotic coupling in oxidative phosphorylation. The model is drawn according to Mitchell s hypothesis for mitochondria, but might also apply to other systems of phosphorylation.

Mitchell, P., "Chemiosmotic Coupling in Oxidative and Photosynthetic Phosphorylation" Glsmn Research Ltd. Bodmin, 1966 Mitchell, P., "Chemiosmotic Coupling and Energy Transduction" Glynn Research Ltd. Bodmin, 1968... 

Mitchell P. Chemiosmotic coupling in oxidative and photosynthetic phosphorylation. Biol Rev Camb Philos Soc 1966 41 445-502. 

Slater, E. C., 1967, An evaluation of the Mitchell hypothesis of chemiosmotic coupling in oxidative and photo synthetic coupling, Eur. J. Biochem. 1 317. 

Mitchell s chemiosmotic theory postulates that the energy from oxidation of components in the respiratory chain is coupled to the translocation of hydrogen ions (protons, H+) from the inside to the outside of the inner mitochondrial membrane. The electrochemical potential difference resulting from the asymmetric dis-... 

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