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Cytochrome Oxidase

©1999 Timothy Paustian, University of Wisconsin-Madison

An animation of cytochrome oxidase. Electrons flow through the CuA site (a copper atom), are donated to heme a and then end up reducing the active site containing heme a3 and CuB (a second copper atom). Oxygen binds to the active site after heme a3 and CuB are reduced with two electrons. Reduction with a third electron causes a change in the binding of the oxygen, forming water and resulting in the translocation of two protons across the membrane. The fourth and final electron helps reduce the final oxygen to water and causes two more protons to move across the membrane. Formation of two water molecules from one oxygen uses four electrons, consumes four protons from the cytoplasm and four more protons are pumped across the membrane. In this animation the protons, electrons and oxygen have been enlarged to improve clarity.

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