Oxidative phosphorylation chemiosmotic model

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.

Before the general acceptance of the chemiosmotic model for oxidative phosphorylation, the assumption was that the overall reaction equation would take the following form ... 

The complete set of equations, describing oxidative phosphorylation according to the chemiosmotic model, is as follows ... 

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. 

Describe the chemiosmotic model of oxidative phosphorylation and relate experimental evidence that only the proton-motive force links the respiratory chain and ATP synthesis. 

Which of the following experimental observations provide evidence supporting the chemiosmotic model of oxidative phosphorylation ... 

The mosaic nonequilibrium thermodynamics formulation of oxidative phosphorylation uses the chemiosmotic model as a basis, besides assuming that the membrane has certain permeability to protons, and that the ATP synthase is a reversible pump coupled to the hydrolysis of ATP. It is assumed that the reversibility of the reactions allows the coupled transfer of electrons in the respiratory chain for the synthesis of ATP, and the proton gradient across the inner mitochondrial... 

In their work on oxidative phosphorylation in mitochondria, Baum et al.(1971) pioneered the use of double inhibitor titration of electron transfer reactions and of ATPase as an approach for the study of the interaction between energy transducers. In the chemiosmotic model, the coupling between two enzyme complexes is mediated by the "delocalized" protons, so that if one of the two transducers is kinetically limiting the overall rate, the inhibition of the other complex should not influence the overall velocity of the process. 

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