respiratory chain complex IV https://github.com/geneontology/go-ontology/issues/27727 cytochrome c oxidase complex electron transport complex IV cellular_component A part of the respiratory chain, containing the 13 polypeptide subunits of cytochrome c oxidase, including cytochrome a and cytochrome a3. Catalyzes the oxidation of reduced cytochrome c by dioxygen (O2). GO:0045277 GO:0045287 cytochrome complex respiratory chain complex transmembrane transporter complex