Figure 1.

Scheme of the two-compartment ME-R model accounting for mitochondrial energetic and redox processes, their interactions, and transport between compartments. The model takes into account OxPhos and matrix-based processes in mitochondria (26,44) as well as in the extra-matrix compartment. In addition to energy metabolism and ion transport (H⁺, Ca²⁺, Na⁺, Pi) the model accounts for O₂^⋅− being produced in the mitochondrial electron transport chain from both complex I- and complex II-derived electron transport. O₂^⋅− may be dismutated to H₂O₂ by superoxide dismutase (MnSOD) in the matrix or be transported as such to the extra-matrix compartment through the inner membrane anion channel, where it will be scavenged by Cu,ZnSOD generating H₂O₂. In the mitochondrial matrix, H₂O₂ can either diffuse outside or be scavenged by the large capacity GSH and Trx systems. In the extra-matrix compartment H₂O₂ may be additionally scavenged by catalase (CAT). Grx accounts for the recovery of glutathionylated proteins in the matrix. Key to symbols: Concentric circles with an arrow across represent the ΔΨ_m. Dotted arrows indicate regulatory interactions either positive (arrowhead) or negative (●−). (Shunt) indicates the fraction of electrons from respiration diverging toward O₂^⋅−. Not indicated in the scheme is the shunt from complex II respiratory substrates.