Thermodynamic and Electrochemical Mitochondrial Cycles (in the Direct and Reverse Directions)

A meta-analysis of the functional states of mitochondria was carried out using a mathematical model based on changes in the direction and speed of thermodynamic (TD) and electrochemical (EC) parameters (pressure, volume, temperature, entropy, Gibbs potential, exergy, etc.), which are interrelated. A mathematical model of the TC and EC cycle of mitochondria was constructed using the basic principle of supramolecular functional interactions. The model describes the TD and EC reactions that occur in the mitochondrial matrix–inner membrane–intermembrane space system and are accompanied by an accumulation of electrochemical potential and charge separation (ionization). Four functional states of mitochondria were studied in the situation where the speed and direction of electron movement along the respiratory chain changed in the thickness of the inner membrane in association with fluctuations in heat flow. The TD and EC cycle of mitochondria is a continuous succession of transitions between quasi-static states, in which quasi-equilibrium states change recurrently, displaying typical coherent stability of non-equilibrium processes according to I. Prigogine. The mathematical model of the TD behavior of mitochondria and the limitations imposed by laws of physical and chemical thermodynamics indicate that the highest degree of TD efficiency in the process of mitochondrial respiration corresponds to the state where Gibbs energy and exergy are at a minimum and entropy is at a maximum; the functional state was consequently identified as a basic one.