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Unformatted text preview: Eyrthrocytes Erythrocytes, or red blood cells (RBCs), transport oxygen (O 2 ) and carbon dioxide (CO 2 ) in the blood. Erythrocytes contain the protein hemoglobin to which both O 2 and CO 2 attach. Mature erythrocytes lack a nucleus and most cellular organelles, thereby maximizing the cell's volume and thus its ability to carry hemoglobin and transport O 2 . Erythrocytes are shaped like flattened donuts with a depressed center (rather than a donut hole). Their flattened shape maximizes surface area for the exchange of O 2 and CO 2 and allows flexibility that permits their passage through narrow capillaries. Hemoglobin contains both a protein portion, called globin, and nonprotein heme groups. Globin consists of four polypeptide chains, each of which contains a heme group. The heme group is a red pigment that contains a single iron atom surrounded by a ring of nitrogen-containing carbon rings. pigment that contains a single iron atom surrounded by a ring of nitrogen-containing carbon rings....
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- Spring '10