Biochemistry of Iron

IRON METABOLISM 11-61 Iron is quantitatively the most important of the biological trace metals. Iron-proteins play a prominent part in the utilization of foodstuffs, both in supplying the tissues with oxygen for respiration and in the respiratory process itself. A normal, adult, 70-kg man contains about 4 gm of iron. Of this about 70% is present as hemoglobin in the blood; about 25% as storage iron, ferritin and hemosiderin; 5% as muscle myoglobin; and the remainder, less than 0.5%, as tissue enzymes and plasma transferrin. The amount of iron present in the human body is subject, however, to considerable variation. It may be reduced to nearly one-third in iron-deficiency anemia or increased to more than ten times its normal value in hemochromatosis. The most dramatic variations occur in the storage compartments which may be reduced to zero in iron deficiency, although the amount of iron present as hemoglobin and other proteins may also be reduced in extreme cases. In