Which Electron-Transferring Reactions in the Respiratory Chain Contribute to the Energy Conservation?

Summary

As starting point for this essay, it is assumed that the energy conserving act coupled with electron transfer in the mitochondrial respiratory chain is the transfer of negative charges from a specific site near the outer face of the inner membrane to a site near the inner face, and/or the transfer of positive charges in the opposite direction, resulting in a charge separation, negative inside. Little is known about which reactions are involved in Site-1 phosphorylation. Present evidence is in favour of the view that the only energy-conserving reactions in Site-2 phosphorylation is the transfer of electrons from ubisemiquinone, bound near the outer membrane, through cytochrome b to ubiquinone bound to the inner face. There is no electrogenic transfer of protons. Wikström's data indicates that in Site 3, about 20% of the charge transfer is due to electron transfer from ferrocytochrome c bound to the outer face to a binuclear centre in the middle of the membrane and 30% to the transfer of protons, required for the reduction of O₂ to H₂O, from the inner compartment to the centre. The remaining 50% is accounted for by the so-called “proton pump”, the nature of which is still obscure.