Iron is the chief among the trace elements required for the body. The total content of iron is very small in the body. In an adult it is approximately 3 to 5 gm. It is widely distributed throughout the body. The major portion of it is found in the blood as hemoglobin. Muscle tissue contain about 3 percent of iron as myoglobin and the rest is stored in the liver, spleen, kidney and bone marrow as ferreting, hemosiderin and siderophilin.
Iron is essential to the processes of oxidation in the body. It is a constituent in compounds necessary for the transport of oxygen to the cells and for oxidation in the cells. In the body iron is present in the blood and liver. The hemoglobin of blood is compound of ‘heme’ an iron compound and ‘globin’, a protein. The synthesis of hemoglobin is based on iron in the body. The function of hemoglobin is to carry oxygen from the lungs to the cells. In lung it is associates with fresh oxygen and forms oxy hemoglobin. During circulation the oxygen is liberated in the cell and oxy hemoglobin becomes hemoglobin again. This is the special property of hemoglobin.
There is a small amount of in the plasma which is bound to a protein called transferring. In case of iron deficiency in the blood the level of plasma iron comes down and anemia occurs.
Iron is present in the muscle cells in two combinations, as myoglobin and a constituent of heme enzymes; myoglobin is a respiratory pigment present in the muscles of vertebrates and invertebrates. It is a compound of iron and protein. Myoglobin has capacity of storing oxygen in the muscle foe use in muscle contractions.
The iron containing enzymes in muscle make the oxidation of carbohydrates, fat and protein possible within the cell. These enzymes are the cytochromes, catalases and peroxides. Each enzyme has the same functions, namely bringing about the oxidative change within the tissue Iron serves in a double capacity in cellular oxidations. It carries oxygen to the cells in hemoglobin and makes oxidation possible in the cells through the iron containing enzymes.