Component of the ubiquinol-cytochrome c oxidoreductase, a multisubunit transmembrane complex that is part of the mitochondrial electron transport chain which drives oxidative phosphorylation. The respiratory chain contains 3 multisubunit complexes succinate dehydrogenase (complex II, CII), ubiquinol-cytochrome c oxidoreductase (cytochrome b-c1 complex, complex III, CIII) and cytochrome c oxidase (complex IV, CIV), that cooperate to transfer electrons derived from NADH and succinate to molecular oxygen, creating an electrochemical gradient over the inner membrane that drives transmembrane transport and the ATP synthase. The cytochrome b-c1 complex catalyzes electron transfer from ubiquinol to cytochrome c, linking this redox reaction to translocation of protons across the mitochondrial inner membrane, with protons being carried across the membrane as hydrogens on the quinol. In the process called Q cycle, 2 protons are consumed from the matrix, 4 protons are released into the intermembrane space and 2 electrons are passed to cytochrome c (PubMed:3015618) (Probable). Cytochrome c1 is a catalytic core subunit containing a c-type heme. It transfers electrons from the [2Fe-2S] iron-sulfur cluster of the Rieske protein to cytochrome c (By similarity). a quinol + 2 Fe(III)-[cytochrome c](out) = a quinone + 2 Fe(II)-[cytochrome c](out) + 2 H(+)(out) Binds 1 heme c group covalently per subunit. Component of the ubiquinol-cytochrome c oxidoreductase (cytochrome b-c1 complex, complex III, CIII), a multisubunit enzyme composed of 10 subunits. The complex is composed of 3 respiratory subunits cytochrome b (cob), cytochrome c1 (cyt-1) and Rieske protein (fes-1), 2 core protein subunits pep and ucr-1, and 5 low-molecular weight protein subunits qcr6, qcr7, qcr8, qcr9 and probably NCU16844/qcr10 (PubMed:226365, PubMed:6273583, PubMed:18251112, PubMed:6302289). The complex exists as an obligatory dimer and forms supercomplexes (SCs) in the inner mitochondrial membrane with NADH-ubiquinone oxidoreductase (complex I, CI) and cytochrome c oxidase (complex IV, CIV), resulting in different assemblies (supercomplexes SCI(1)III(2), SCIII(2)IV(1) and SCIII(2)IV(2) as well as higher order I(x)III(y)IV(z) megacomplexes) (PubMed:17873079, PubMed:19239619). Belongs to the cytochrome c family.