Health Tooty Fruity

Hemoglobin and myoglobin are proteins that transport and store oxygen. Heme is a compound found in both of these proteins. Hemoglobin is composed of four units; each unit has a protein chain and a heme group. Myoglobin has one protein chain and one heme group. Heme is a compound that has iron in the center, as seen in Figure 11-1.

Hemoglobin is the most important protein found in red blood cells. About two-thirds of the iron in the body (about 2.5 grams) is inside the heme found in hemoglobin, as seen in Figure 11-2. Hemoglobin has the unique ability to very rapidly acquire oxygen from the lungs. Hemoglobin then transports oxygen to the rest of the body. Hemoglobin releases oxygen as needed as the blood moves through the tissues.

Myoglobin (myo means muscle) is a protein that contains heme and is found in muscle cells. About 15 percent of the iron in the body is found in myoglobin. Myoglobin has a great affinity for oxygen, which it binds and holds. The oxygen






Figure 11-1 Heme in red blood cells with iron(Fe) in the center.


Figure 11-2 Iron distribution in the body.

is bound directly to the iron atom inside myoglobin. The myoglobin then stores the oxygen inside muscle cells. When oxygen is not readily available from blood, myoglobin releases its stored oxygen for the use of the muscle cell.