AAB MT Hematology

AAB MT Hematology What is hemoglobin composed of? - ANSWER 4 heme, 4 iron, 4 globins What disorder does a defect in heme synthesis lead to? - ANSWER Porphyria Porphyria - ANSWER Deficiency in the enzymes of the porphyrin pathway leads to insufficient production of heme. The principal problem in these deficiencies is the accumulation of porphyrins, the heme precursors, which are toxic to tissue in high concentrations. What is methemoglobin? - ANSWER Methemoglobin is a form of hemoglobin that contains ferric [Fe3+] iron and has a decreased ability to bind oxygen. However, the ferric iron has an increased affinity for bound oxygen. When methemoglobin concentration is elevated in red blood cells, tissue hypoxia can occur. What is the function of the enzyme methemoglobin-cytochrome C reductase in a red blood cell? - ANSWER To keep iron in the ferrous state What product is formed when ferrous iron of hemoglobin is oxidized to the ferric state? - ANSWER Methemoglobin What is carboxyhemoglobin? - ANSWER A stable complex of carbon monoxide and hemoglobin that forms in RBCs when carbon monoxide is inhaled or produced in normal metabolism. Large quantities of it hinder delivery of O2 to the body. Tobacco smoking (through carbon monoxide inhalation) raises the blood levels of COHb by a factor of several times from its normal concentrations. Which hemoglobin has a 200 times greater binding capacity for the hemoglobin molecule than oxygen? - ANSWER Carboxyhemoglobin Which hemoglobin derivative causes irreversible changes in RBCs? - ANSWER Sulfhemoglobin -- makes blood incapable of carrying ox