<P> Human iron metabolism is the set of chemical reactions maintaining human homeostasis of iron at both the systemic and cellular level . The control of this necessary but potentially toxic metal is an important part of many aspects of human health and disease . Hematologists have been especially interested in systemic iron metabolism because iron is essential for red blood cells, where most of the human body's iron is contained . Understanding iron metabolism is also important for understanding diseases of iron overload, such as hereditary hemochromatosis, and iron deficiency, such as iron deficiency anemia . </P> <P> Iron is an essential bioelement for most forms of life, from bacteria to mammals . Its importance lies in its ability to mediate electron transfer . In the ferrous state, iron acts as an electron donor, while in the ferric state it acts as an acceptor . Thus, iron plays a vital role in the catalysis of enzymatic reactions that involve electron transfer (reduction and oxidation, redox). Proteins can contain iron as part of different cofactors, such as iron - sulfur clusters (Fe - S) and heme groups, both of which are assembled in mitochondria . </P> <P> Human cells require iron in order to obtain energy as ATP from a multi-step process known as cellular respiration, more specifically from oxidative phosphorylation at the mitochondrial cristae . Iron is present in the iron - sulfur clusters and heme groups of the electron transport chain proteins that generate a proton gradient that allows ATP synthase to synthesize ATP (chemiosmosis). </P> <P> Heme groups are part of hemoglobin, a protein found in red blood cells that serves to transport oxygen from the lungs to the tissues . Heme groups are also present in myoglobin to store and diffuse oxygen in muscle cells . </P>

The iron storage and iron transport proteins are