A heme protein that transfers electrons,and exhibits intense absorption bands (the 
and 
bands, the band having the longer wavelength) between 510 and 615 nm in the reduced form. Cytochromes are designated types a, b, c or d, depending on the position of the band, which depends on the type of heme. The iron undergoes oxidation-reduction between oxidation states Fe(II)and Fe(III). Most cytochromes are hemochromes, in which the fifth and sixth coordination sites in the iron are occupied by strong field ligands, regardless of the oxidation state of iron. Cytochromes may be distinguished by the wavelength of the band, such as cytochrome c-550. Certain specific cytochromes with particular functions, are designated with suffixes, such as cytochrome a1,b2, etc., but this practice is discouraged.
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