Figure 1.

Production of ATP and ROS by the electron transport chain. Nutrients in the form of glucose, fatty acids, or amino acids are converted into the Krebs cycle intermediates and then oxidized by 8 different enzymes. During carbon oxidation electrons are extracted and ferried through the respiratory complexes to drive ATP production (OXPHOS). Electrons from the Krebs cycle enter the respiratory chain via NADH at Complex I or succinate at Complex II. Electron flow to the terminal acceptor di-oxygen which creates the transmembrane electrochemical potential of protons which drives ATP production by Complex V. Red circles: represent major sites for ROS production in mitochondria (Univalent reduction of di-oxygen (O₂) to H₂O. The standard redox potentials for each univalent reduction of O₂, O₂•⁻, H₂O₂, and OH•^. are indicated in the diagram). Pdh; pyruvate dehydrogenase, Odh; 2-oxoglutarate dehydrogenase, I, Complex I; II, Complex II; III, Complex III; IV, Complex IV; V, Complex V; ANT, adenine nucleotide translocase; VDAC, voltage-dependent anion channel.