Membrane bound hemoprotein which function as an electron carrier for several membrane bound oxygenases. It plays a role in fatty-acid desaturation and is also involved in several steps of the sterol biosynthesis pathway, particularly in the 4-demethylation of the 4,4'-dimethyl zymosterol. Present with 5390 molecules/cell in log phase SD medium. Belongs to the cytochrome b5 family.