Cytochrome c oxidase

Cytochrome c oxidase is the terminal enzyme complex of the mitochondrial respiratory chain. It transfers electrons from cytochrome c to oxygen, reduces oxygen to water, and pumps protons across the inner mitochondrial membrane.

Cytochrome c: A small heme protein that carries electrons between respiratory-chain complexes and other cellular enzymes. It donates the electrons that cytochrome c oxidase passes to oxygen.
Electron transport chain: A series of membrane-associated protein complexes that transfer electrons and help establish a proton gradient. Cytochrome c oxidase is the chain's terminal complex.
Cellular respiration: The set of metabolic reactions by which cells extract energy from nutrients and produce ATP. The enzyme performs the final oxygen-dependent step of mitochondrial respiration.
Mitochondrial DNA: The small, usually circular genome found in mitochondria, encoding a limited set of proteins and RNAs. It encodes core cytochrome c oxidase subunits, including subunit I.
Oxygen reduction: The gain of electrons by molecular oxygen, producing water or partially reduced oxygen compounds. Cytochrome c oxidase completes respiration by reducing oxygen to water.
Mitochondrial inner membrane: The selectively permeable membrane that encloses the mitochondrial matrix and houses respiratory-chain complexes. The enzyme is embedded here and pumps protons across it.
ATP synthase: A membrane enzyme that uses proton flow down an electrochemical gradient to synthesize ATP. It uses the gradient to which cytochrome c oxidase contributes.
Nuclear DNA: The DNA contained in a cell's nucleus, encoding most cellular proteins. Most cytochrome c oxidase subunits and assembly factors are encoded in the nucleus.
Proton pumping: The transport of protons across a membrane, driven by an energy-releasing process. The enzyme couples electron transfer to proton movement across the inner mitochondrial membrane.
Complex I: A respiratory-chain complex that transfers electrons from NADH to ubiquinone while pumping protons. It begins one major electron-entry route that ultimately supplies cytochrome c oxidase.

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