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Question: 2 the chemical basis of life case study defects in...

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2 The Chemical Basis of Life CASE STUDY: Defects in Hemoglobin Structure and Function Hemoglobin is the major oxygen carrier that is used to deliver oxygen to our tissues. It is a heterotetrameric protein that is composed of two alpha subunits and two beta subunits. Each subunit has the ability to bind and release oxygen, and its ability to do so is influenced by the structure of the other subunits. Defects in hemoglobin structure or synthesis are collectively termed hemoglobinopathies. This group of diseases results from either defects in the synthesis of one of the hemoglobin chains or in defects in the structure of the hemoglobin molecule itself. Patients with defective hemoglobin have characteristic anemia, which leads to pallor, fatigue, and shortness of breath. Other clinical manifestations include reticulocytosis (elevation of the number of young red blood cells), splenomegaly (enlarged spleen), and urobilinuria (excess urobilins, which are breakdown products of hemoglobin, in the urine). Sickle Cell Anemia is a specific type of hemoglobinopathy caused by mutation of a single glutamic acid residue on the surface of hemoglobin to a valine, which results in a change in the surface properties of hemoglobin. This mutant hemoglobin is referred to as HbS. Presence of HbS causes protein aggregation under conditions of deoxygenation. The protein aggregates lead to malformed red blood cells that inhibit capillary flow. Questions: 1· The mutation in hemoglobin is a change from a glutamic acid to a valine, what are the chemical features of these two amino acids that may result in the defects caused by HbS 2. According to the principles of the hydrophobic effect, where should glutamic acid and valine normally be found in proteins? 3. How then do you think that the mutated valine residue can contribute to the aggregation of hemoglobin molecules in HbS?
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