Simultaneous Measurement of Oxygen Consumption Rate and Thermogenesis in Biological Systems for Non-equilibrium Energetics

Abstract

We have recently proposed a theoretical model for the mechanism of heat production in the mitochondrial respiratory chain, derived from the overpotential of electrochemical reactions in enzyme catalysis. A key feature of this overpotential-derived thermogenesis model is that the distribution of energy consumption between thermogenesis and adenosine triphosphate synthesis changes depending on the reaction rate. To verify that similar energy partitioning occurs in other metabolic reactions linked to the respiratory chain, we developed a system for the simultaneous measurement of thermogenesis and respiration rate in yeast cells. We correlated the amount of thermogenesis with the respiration rate, finding that most thermogenesis in yeast cells is derived from fermentation, which is connected to the respiration rate. By investigating the relationship between fermentative heat production and respiration rate, we discovered that the energy partitioning between heat production and substance synthesis exists and changes depending on the respiration rate. This strongly suggests the existence of electrochemical overpotential-derived thermogenesis in metabolic processes.