The protonmotive force and respiratory control : Building blocks of mitochondrial physiology Part 1

Clarity of concepts and consistency of nomenclature are trademarks of the quality of a research field across its specializations, facilitating transdisciplinary communication and education. As research and knowledge on mitochondrial physiology expand, the necessity for harmonization of nomenclature on mitochondrial respiratory states and rates has become apparent. Peter Mitchell’s concept of the protonmotive force establishes the link between the electric and chemical components of energy transformation and coupling in oxidative phosphorylation. This unifying concept provides the framework for developing a consistent terminology on mitochondrial physiology and bioenergetics. We follow IUPAC guidelines on general terms of physical chemistry, extended by concepts of open systems and irreversible thermodynamics. We align the nomenclature of classical bioenergetics on respiratory states with a concept-driven constructive terminology to address the meaning of each respiratory state. Hence we focus primarily on the conceptual ‘why’ along with clarification of the experimental ‘how’. The capacity of oxidative phosphorylation, OXPHOS, provides diagnostic reference values and is, therefore, measured at kinetically saturating concentrations of ADP, inorganic phosphate and fuel substrates. The contribution of intrinsically uncoupled oxygen consumption is most easily studied by arresting phosphorylation, when oxygen consumption compensates mainly for the proton leak, and the corresponding states are collectively classified as LEAK states. The oxidative capacity of the electron transfer system, ETS, reveals the limitation of OXPHOS capacity mediated by the phosphorylation system. Experimental standards for evaluation of respiratory coupling states must be followed for the development of databases of mitochondrial respiratory function in diverse physiological and experimental conditions and organisms. This page contains no comments