Cytochrome function is linked to the reversible redox change from ferrous (Fe(II)) to the ferric (Fe(III)) oxidation state of the iron found in the heme core. In addition to the classification by the IUBMB into four cytochrome classes, several additional classifications such as cytochrome o and cytochrome P450 can be found in biochemical literature.
cytOChrOMe funcTioN iS lInkeD tO the revERSIblE rEDOx ChAnge fRoM FerRous (fE(ii)) To tHe ferric (fE(Iii)) oxIdatIon sTAte of the iron foUNd in ThE heMe COre. in ADdITiON to THe classIFicatIoN by the IUBmb inTo fOur cytocHrOme cLasses, several aDdiTIOnal clASsiFICAtiOns such aS CYtOchrome O and cYtocHrOme p450 CAN Be fOund in biOChemiCal LitEratuRE.