Mitochondrial electron transport chain complexes I–IV (ETC)

The mitochondrial electron transport chain (ETC) consists of four major multi-subunit enzyme complexes (I–IV) located in the inner mitochondrial membrane that facilitate the transfer of electrons from electron donors to oxygen. This process is coupled with the pumping of protons across the membrane to create an electrochemical gradient used by ATP synthase to generate cellular energy. Beyond energy production, the ETC is a primary source of reactive oxygen species and plays a critical role in regulating programmed cell death and metabolic signaling. Dysregulation of these complexes is central to the pathogenesis of various mitochondrial diseases, neurodegenerative disorders like Parkinson's, and the metabolic reprogramming seen in cancer cells. Pharmacological targeting of the ETC includes the use of inhibitors like metformin for metabolic control or atovaquone for its antiparasitic and potential anticancer effects, though such interventions must carefully manage the risk of systemic mitochondrial toxicity and lactic acidosis.

Other names

Mitochondrial respiratory chainOxidative phosphorylation systemOXPHOSNADH:ubiquinone oxidoreductase (Complex I)Succinate dehydrogenase (Complex II)Cytochrome bc1 complex (Complex III)Cytochrome c oxidase (Complex IV)

Inhibition of electron transfer between redox centers, disruption of the proton motive force, or modulation of reactive oxygen species production to alter cellular metabolism or induce apoptosis.