Cytochrome c. Computer artwork of the molecular structure of the protein cytochrome c550. The secondary structure of alpha helices is shown, along with the haem group (sticks) containing its iron atom (red). Cytochrome molecules perform oxidation and reduction reactions for electron transport, a chain of reactions used to power cellular processes that require energy. The iron ion accepts the electron. As cytochromes perform a key step in the production of energy they are found in all living organisms, however simple or complex.