Potentials of the Respiratory Chain Elements

Calculation of the change in the free energy of redox reactions taking place in complexes and its comparison with that accepted for reactions in solutions indicates that in the presence of cooperativeness in the electron transfer or in the absence of an equilibrium with the medium, a conventional thermodynamics analysis 

Although a thermodynamic analysis of the functioning of the respiratory chain should be conducted using methods of nonequilibrium thermodynamics, in practice it is the so-called midpoints potentials determined by the method of potentiometric titration with the use of mediators13 that are used for characterizing the redox properties of the components of the respiratory chain. The method devised for this purpose is founded on the supposition that the mediator is oxidized or reduced only by the chain components of interest to us. The correctness of this supposition is usually controlled by independent methods, as for instance, the spectroscopic or ESR method. 

A table of the redox potentials of the components of the respiratory chain of mitochondria obtained this way is given below.13 

Each result was obtained on a number of appropriate mediators, not just one, and therefore does not depend on the nature of the mediator and its concentration (See Table 1). Table 1 shows that all the components can be divided into four groups according to their potentials with potentials of -300, 0, 230, and 

The Half-Reduction Potentials of the Components of the Mitochondrial Respiratory Chain (mV), pH = 7.2  

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