How iron is transported in our body?

Iron is present in the human body in several types of molecules. Most of these molecules are chelates of iron. These chelates play vital roles in several physiological processes in body cells.

Iron is an essential element in human metabolism involved in many biological functions ranging from oxygen transport to various enzymatic reactions.

Iron circulates in the plasma in a variety of forms. The major form is bound to the glycoprotein transferrin. This protein is found at highest concentrations in the serum, cerebral spinal fluid, and joint fluid but also can be detected in mucosal membranes, particularly in inflamed tissue.

In addition, there is a pool of minor forms, termed ‘non-transferrin bound iron’, which includes iron bound to low molecular weight chelators, macromolecules and other proteins.

Iron bound to plasma transferrin is mainly derived from red blood cells which have been broken down in the spleen, and is in the process of being delivered to the bone marrow where it is efficiently re-incorporated into new red blood cells.

Other form of plasma iron include nonheme and heme iron. Ferritin-iron is likely to represent only a minute amount of total body iron, as the iron content of circulating ferritin is usually low.

Heme iron is carried as hemoglobin bound to haptoglobin and as heme bound to hemopexin. Heme iron is the iron present in myoglobin, hemoglobin and related compounds.

From these compounds, the heme is released by proteolytic enzymes in the gut. From the lumen the heme is transported inside the enterocyte across the brushborder membrane by an unindentified heme transport protein.
How iron is transported in our body?