The reduction of iron (III) to iron(II) has a cell potential of 0.271 volts. This reduction is only 0.254 volts in cytochrome c. it is 0.220 volts in cytochromec1. it is 0.071 volts in cytochrome b, and only 0.02volts in cytochrome b5.for a few examples. Why can the reduction potential change based upon the cytochrome?
The Cytochromes associated with the electron transport system (oxidation part of oxidative phosphorylation) all contain iron in either the 2+ or 3+ oxidation state, and can switch from one to the other.