Thermodynamic and Kinetic Aspects of the Interconversion of Chemical and Osmotic Energies in Mitochondria

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Abstract
The conversion of osmotic energy into ATP has the following properties:a) K+, as effluent ion, can be replaced by Rb+, whereas when H+, as influent, is replaced by other cations, the synthesis is abolished.b) Both the effluent cation and the influent H+ seem to provide energy for the synthesis. The minimal sum of ΔpH +ΔpK, compatible with the synthesis, is 2.5 units, corresponding to an osmotic potential of 3.45 kcalories per gram‐ion equivalent−1. The number of ion equivalents exchanged per ATP synthesized is dependent on the dimension of the osmotic potential.c) The osmotic potential compatible with the ATP synthesis is partially affected by the phosphate potential. The conversion of redox into osmotic energy has the following properties:a) The number of K+ ion equivalents exchanged with protons per energy rich bond is dependent on the concentrations of H+ and K+ in the inner and outer aqueous phases, increasing up to a maximal value of 4.b) The number of K+ ion equivalents exchanged with protons per energy rich bond increases parallel to the increase of the amount of valinomycin, up to the value of 4. On the basis of available data the following thermodynamic parameters are evaluated:a) The relationship between osmotic potential and ATP synthesis.b) The relationship between redox and osmotic energy.c) The osmotic potential barrier for ion translocation. A molecular mechanism for the interconversion of osmotic and chemical energies is discussed.