Overpotential-derived thermogenesis in mitochondrial respiratory chain

Thermogenesis, which is associated with intracellular aerobic respiration, is a fundamental function that controls the internal temperatures of living organisms. Proton leakage is considered to be correlated with thermogenesis through aerobic respiration. It is widely known that in electrochemical cells such as fuel cells, overpotentials applied to redox reactions generate heat as energy loss. Even in the electrochemical reaction system of the mitochondrial respiratory chain, a considerable amount of heat is generated by overpotential. However, the physical mechanism of thermogenesis is not yet clear. We propose a thermogenesis model based on the electrochemical overpotential of the mitochondrial respiratory chain. As a result of quantitatively estimating the value of the overpotential applied in each reaction of the mitochondrial respiratory chain, we found that 39-63% of the initial free energy in the respiratory chain was converted into heat, and the rate of thermogenesis changed depending on respiratory activity. Furthermore, that heat was intensively produced in complex IV. The overpotential-derived thermogenesis model is expected to open a research field for electrochemically elucidating mitochondrial functions.