Heme is a member of a family of compounds called porphyrins . Heme synthesis occurs partly in the mitochondria and partly in the cytoplasm. The process begins in the mitochondria because one of the precursors is found only there. Most of the intermediate steps are cytoplasmic. Summary of regulation of heme synthesis.
Porphyrias are defects in porphyrin metabolism.
Heme degradation is an important metabolic process. Iron metabolism is shaped by iron's status as an essential nutrient for which there is no mechanism for excreting any excesses that may accumulate in the body. Iron absorption is affected by the form in which iron is presented to the digestive tract, and inorganic iron ions change oxidation state during the absorption process. Regulation of iron uptake occurs at the basal membrane of the intestinal mucosal cells. These cells make an iron-binding protein, apoferritin.