Hemoglobin: The oxygen-carrying pigment and predominant protein in the red blood cells. Hemoglobin forms an unstable, reversible bond with oxygen. In its oxygenated state it is called oxyhemoglobin and is bright red. In the reduced state it is called deoxyhemoglobin and is purple-blue.
Each hemoglobin molecule is made up of four heme groups surrounding a globin group. Heme contains iron and gives a red color to the molecule. Globin consists of two linked pairs of polypeptide chains. The development of each chain is controlled at a separate genetic locus. Changes in the amino acid sequence of these chains results in abnormal hemoglobins. For example, hemoglobin S is found in sickle-cell disease, a severe type of anemia in which the red cells become sickle-shaped when oxygen is in short supply.
When red blood cells die, the hemoglobin within them is released and broken up: the iron in hemoglobin is salvaged, transported to the bone marrow by a protein called transferrin and used again in the production of new red blood cells; the remainder of the hemoglobin becomes a chemical called bilirubin that is excreted into the bile which is secreted into the intestine, where it gives the feces their characteristic yellow-brown color.
Library > Literature & Language > Dictionary ( hÄ“ ' mÉ™-glÅ ' bÄn ) n. ( Abbr. Hb or hg or hgb. ) The iron-containing respiratory pigment in red blood cells of ...
Medical Author: Siamak Nabili, MD, MPH Medical Editor: William C. Shiel, Jr., MD, FACP, FACR. What is hemoglobin? How is hemoglobin measured? What are normal hemoglobin values?
Describes how a hemoglobin test is used, when a hemoglobin test is ordered, and what the results of a hemoglobin test might mean
3-dimensional structure of hemoglobin. The four subunits are shown in red and yellow, and the heme groups in green.
Hemoglobin is a protein in red blood cells that carries oxygen. A blood test can tell how much hemoglobin you have in your blood. Veins and arteries vary ...