Haem
Heme (haem) is a cofactor for several heme-containing proteins that function in oxygen binding or metabolism as well as in electron transport. Hemes are most commonly recognized as components of hemoglobin, the red pigment in blood, but are also found in a number of other biologically important hemoproteins such as myoglobin and cytochromes, and many others. Hemoglobins are the primary oxygen-binding proteins.The organs mainly involved in heme synthesis are the liver (highly variable rate of synthesis) and the bone marrow (in which rate of synthesis of Heme is relatively constant).