Respiratory pigments found widely in aerobic organisms. They consist of proteins with an iron prosthetic group similar to that of hemoglobin. The oxidation of cytochromes by molecular oxygen, and their subsequent reduction in the cell, is the principal route by which atmospheric oxygen enters into c...
Heme oxidation-reduction reactions such as photosynthesis and respiration. ... (09 Oct 1997) ... 
Proteins essential for oxidation-reduction processes in cells.Enzymes of the electron transport chain that are pigmented by virtue of their haemprosthetic groups. Very highly conserved in evolution.