8. Compare the job of the abnormal hemoglobin protein that causes sickle cell disease to the normal hemoglobin protein. Explain how this causes sickle cell disease.
Hemoglobin is a protein found in red blood cells that carries oxygen from the lungs to the body's tissues and carbon dioxide from the tissues to the lungs. In sickle cell disease, an abnormal hemoglobin protein is produced, which causes red blood cells to change their shape and become sickle-shaped instead of the normal biconcave shape. This abnormal shape of red blood cells causes several problems in the body.
Normal hemoglobin protein is composed of four subunits, two alpha-globin chains, and two beta-globin chains, each of which contains a heme group that binds to oxygen. In contrast, sickle hemoglobin (HbS) is caused by a single amino acid substitution in the beta-globin chain, where a valine replaces a glutamic acid residue at the sixth position. This change in the amino acid sequence of the beta-globin chain causes HbS to stick together under low oxygen conditions, forming long, rigid fibers that distort the shape of red blood cells.
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