Figure 1 - Organization of the branched respiratory chain of plant mitochondria. Complex I, NADH dehydrogenase; complex II, succinate dehydrogenase; complex III, cytochrome bc1; complex IV, cytochrome oxidase; AOX, alternative oxidase; c, cytochrome c; Q, ubiquinone; QH2, ubiquinol; INT, internal NAD(P)H dehydrogenase; EXT, external NAD(P)H dehydrogenase.