The Crucial Role of Iron in the Body
You learned from the "Hemoglobin and the Heme Group: Metal Complexes in the Blood" tutorial that iron is necessary for oxygen transport in the blood. Recall that iron is the central atom of the heme group, a metal complex that binds molecular oxygen (O2) in the lungs and carries it to all of the other cells in the body (e.g., the muscles) that need oxygen to perform their activities. Without iron in the heme group, there would be no site for the oxygen to bind, and thus no oxygen would be delivered to the cells (which would result in the cells dying). In addition to hemoglobin, other important proteins in the body that contain heme groups (and therefore contain iron) include myoglobin, which takes oxygen from hemoglobin and allows the oxygen to diffuse throughout the muscle cells, and the cytochromes, which supply the body with its energy currency. (You will learn more about cytochromes in the Chem 152 tutorial, "Energy for the Body: Oxidative Phosphorylation".) Other proteins, such as those needed for DNA synthesis and cell division, also rely on iron. Furthermore, iron is used to help produce the connective tissues in our body, some of the neurotransmitters in our brain, and to maintain the immune system. Hence, iron is necessary for allowing the cells that need oxygen to obtain O2, for supplying the body with a reliable source of energy, and for maintaining several other important structures and systems in the body.
Because iron plays such a crucial role in the body, it is important for us to maintain an adequate supply of iron to form hemoglobin and the other molecules in the body that depend on iron to function properly. Yet, our bodies continually lose iron (in small amounts) through everyday process such as urination, defecation, sweating, and sloughing off skin cells. Bleeding, particularly menstrual bleeding in women, contributes to further loss of iron from the body. To compensate for these losses and to maintain an adequate supply of iron, we should consume approximately 18 mg of iron daily. Certain conditions, including heavy bleeding and pregnancy, further increase the requirement for iron consumption. Good dietary sources of iron include red meat, liver, egg yolk, beans, nuts, and fortified cereals.
When the body's supply of available iron is too low, a condition known as iron deficiency results. People with iron deficiency cannot produce an adequate amount of hemoglobin to meet their body's oxygen-transport needs. When the deficiency becomes severe (so that there are too few circulating red blood cells or the hemoglobin content of these cells is very low), the condition is diagnosed as iron-deficiency anemia. The most common symptoms of iron-deficiency anemia are tiredness and weakness (due to the inadequate oxygen supply to the body's cells) and paleness in the hands and eyelids (due to the decreased levels of oxygenated hemoglobin, which is red-colored). Iron-deficiency anemia can be treated with iron supplements, and by adopting strategies to improve the body's absorption of the iron in the supplements (e.g., taking iron with vitamin C, which enhances absorption, but not with milk, which limits absorption).
It is also possible to have too much iron deposited in the body tissues. This condition is known as iron overload. If the iron overload becomes severe (usually when the total amount of iron in the body exceeds 15 g), the condition is diagnosed as hemochromatosis. Hemochromatosis can result in serious damage to the body's tissues, including cirrhosis of the liver, heart failure, diabetes, abdominal pain, and arthritis. A recessive genetic mutation can put some people (e.g., those of Irish or Celtic descent) at a higher risk for developing hemochromatosis. Treatment for hemochromatosis consists of removing blood from the patient to decrease the amount of iron in the body, and treating the symptoms (e.g., liver disease and diabetes).
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This page created by Matt Traverso, Washington University in St Louis.
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