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Hemoglobin

Hemoglobin is an oxygen-carrying protein, and acts as such in most mammals (Friedman 1273). Typically, hemoglobins have a tetrameric structure consisting of two ? polypeptide chains of 141 amino acids each and two ? polypeptide chains of 146 amino acids each, with each subunit containing an iron-porphyrin (heme) oxygen-binding site (Friedman 1273). Each polypeptide chain forms a ball around a heme group (Hardison 128). Hemoglobin is a very abundant protein in mammals, and gives red blood cells their color when it binds oxygen (Hardison 128). Hemoglobin binds oxygen in the lungs and transports it to tissues in the body which require it for respiration (Hardison 128). An oxygen carrier is needed because oxygen is not sufficiently soluble in plasma to supply the needs of the tissues of the body (Devlin 1026). If one was not present, the blood would have to circulate 87 times as fast as it does to supply the oxygen needs of the body (Devlin 1026).

Hemoglobin A is the major hemoglobin found in adult humans, comprising about 90 percent of their total hemoglobin (Devlin 1030). Two to three percent of adult hemoglobin is hemoglobin A2, which has two ? chains and two ? chains, which differ in amino acid sequence to ? chains and are under independent genetic control (Devlin 1030). There are several modified version of hemoglobin A in the human, most with sugars such as glucose, glucose-6-phosphate or fructose 1,6-bisphosphate bound to them. The most significant is hemoglobin A1C, hemoglobin with glucose bound covalently to the N terminal of the ? chain (Devlin 1030). This hemoglobin is present in uncontrolled diabetes, and its measurement can be used to monitor diabetic blood sugar control (Devlin 1030).

Hemoglobin F is the major hemoglobin present in the newborn, and contains two ? chains and two ? chains (Devlin 1030). Gamma chain synthesis declines shortly before birth, and ? chain synthesis begins: by the age of seven ...

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Hemoglobin. (1969, December 31). In LotsofEssays.com. Retrieved 19:46, March 28, 2024, from https://www.lotsofessays.com/viewpaper/1701078.html