Thermodynamic relationships between the oxidation-reduction reactions and the ATP synthesis in suspensions of isolated pigeon heart mitochondria

The freeEnergy change of the transfer of the reducing equivalents between the NADH and cytochrome c equals the free energy change required to synthesize 2 moles of ATP outside the mitochondria, indicating that the coupled reactions remain in near equilibrium.

Abstract

Studies on the suspension of isolated pigeon heart mitochondria demonstrate that the mitochondrial respiratory chain consists of isopotential groups of components. The transfer of the reducing equivalents between two neighboring groups is coupled to the synthesis of ATP. The free energy change of the transfer of the reducing equivalents between the NADH and cytochrome c equals, within experimental error, the free energy change required to synthesize 2 moles of ATP outside the mitochondria. This indicates that the coupled reactions remain in near equilibrium. The Keq for the first two phosphorylation sites in State 4 is 6.8 × 106m−2 and is very close to the theoretical value (3.2 × 106m−2).