erinevatest alaühikutest koosnev valguline kompleks mitokondrite elektrontranspordi ahelas, mis katalüüsib redutseeritud tsütokroomi c oksüdeerumist ja hapniku redutseerumist vee tekkega, millega kaasneb prootonite liikumine maatriksist membraanide vaheruumi ja prootonite gradiendi tekkimine ATP sünteesiks, Multi-subunit protein complex in the mitochondrial electron transport chain, catalyzes the oxydation of reduced cytochrome c and reduction of oxygen with the formation of water, that in turn cause the movement of protons from the mitochondrial matrix to the intermembrane space and formation of the proton gradient.