Heme metabolism is an important metabolic process because
many important proteins contain heme
as a prosthetic group. When these hemoproteins turn over, the heme is
not salvaged, but is degraded. New heme is synthesized for their
replacements.
Heme is a member of a family of compounds called porphyrins. (text, sound, graphics, animation with sound)
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. Since this reaction is regulated in part by the
concentration of heme, the final step (which produces the heme) is also
mitochondrial. Most of the intermediate steps are cytoplasmic. (text,sound, graphics)
Summary of regulation of heme synthesis. (text)
Porphyrias are defects in porphyrin metabolism. (text,sound, graphics)
Heme degradation is an important metabolic process. (text,sound, graphics)
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. (text)
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. (text, graphics)
Regulation of iron uptake occurs at the basal membrane of the intestinal mucosal cells. These cells make an iron-binding protein, apoferritin. (text, graphics)
Iron transport and storage
involve changes of oxidation state. The capacity of the plasma to
transport iron is of clinical interest. Excess stored iron can cause
pathology. (text, graphics)
Test yourself with some multiple choice exam questions. (text)
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