Copper is essential to antioxidant defenses, brain function, collagen synthesis, and it plays a key role in energy metabolism. The role that copper plays in energy metabolism is sometimes overlooked. In the inner mitochondrial membrane, cytochrome c oxidase catalizes the rate-limiting terminal step of oxidative phosphorylation (see Fig. 4). The copper, in subunit II of this complex, transfers the electrons from cytochrome c to the copper and iron containing center of the catalytic subunit 1. A vectoral Bohr mechanism (conformation shift due to oxygenation change) moves reduced protons from the inner aqueous space through the mitochondrial membrane and the heme-copper oxidases then release them into the external space [ Papa S., et al, Biochimie, 1998 Oct;80(10):821-36]. This proton translocation builds up a proton gradient or pump across the inner mitochondrial membrane that drives the synthesis of the energy dynamo, ATP.