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8 Cards in this Set
- Front
- Back
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What is hemoglobin A?
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It is normal adult human hemoglobin. The two types of polypeptide are called the alpha chains, each containing 141 AA residues, and the B chains each containig 146 AA residues.
Thus hemoglobin A is a2b2. |
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Is all the hemoglobin in the blood of normal adults hemoglobin A?
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No. About 2.5% of the hemoglobin is hemoglobin A2, in which beta chains are replaced by theta chains(a2theta2).
The theta chains also have 146 AA residues, but 10 individual residues differ from those in the beta chains. |
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There are small amounts of hemoglobin A derivatives closely associated with hemoglobin A that represent glycated hemoglobins. TRUE/FALSE
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TRUE. One of these(hemoglobin A1c)(HbA1c) has a glucose attached to the terminal valine in each beta chain and is of special interest because the quantity in the blood increases in poorly controlled diabetes mellitus.
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Hemoglobin binds to O2 to form oxyhemoglobin, O2 attaching to the Fe2+ in the heme. TRUE/FALSE
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TRUE. The affinity of Hb for O2 is affected by pH, temperature and the concentration in the red cells of 2,3 biphosphoglycerate.
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2,3 BPG and H+ compete with O2 for binding to deoxygenated hemoglobin. TRUE/FALSE
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TRUE. There is a decrease of affinity of hemoglobin for o2 by shifting the positions of the 4 peptide chains(quartenary structure).
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What is a potential result when blood is exposed to various drugs and other oxidizing agents?
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The ferrous iron(Fe2+) that is normally in the molecule is converted to ferric iron(Fe3+) forming methmoglobin.
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What is a color characteristic of methmoglobin?
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It is dark colored, and may cause a dusky discoloration of the skin.
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Is methmoglobin ever reconverted naturally to hemoglobin?
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Yes. Some occurs naturally, but there is an enzyme system in the RBC, the NADH-methmoglobin reductase system, converts methmoglobin back to Hb. Absence of this system results in hereditary methmoglonemia.
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