Category: catabolism
Mitochondrial inner-membrane electron transport chain coupled to chemiosmotic ATP synthesis. Complex I (NADH:CoQ oxidoreductase) — NADH → CoQ; METFORMIN TARGET. Complex II (succinate dehydrogenase = TCA enzyme) — succinate → CoQ; doesn't pump protons. Complex III (CoQ:cytochrome c oxidoreductase) — Q-cycle pumps protons. Complex IV (cytochrome c oxidase) — final O2 reduction; CYANIDE + carbon monoxide target. Complex V (ATP synthase) — H+ flow drives ATP synthesis; OLIGOMYCIN target. Uncouplers (2,4-DNP historic, fatal hyperthermia) collapse the H+ gradient → heat instead of ATP. Mitochondrial myopathies / encephalopathies (MELAS, MERRF, LHON) arise from mutations in mtDNA-encoded ETC subunits.