SSimonPractice206[1]

SSimonPractice206[1] - _ Name and ID# (usually your Social...

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_________________________________________________ ______________________ Name and ID# (usually your Social Security Number) 1. (3 points) You have discovered a new mutant human hemoglobin with properties virtually identical to those found in hemoglobin S. You would most likely find: a. there is an increased energy barrier to the quaternary conformational change in the mutant. b. the oxygen affinity of the mutant hemoglobin is increased. C . there is a hydrophobic patch on the surface which is exposed in the deoxygenated mutant and is not present in normal hemoglobin A. d. the mutant hemoglobin binds 2,3-DPG with less affinity than hemoglobin A. The substitution of val for glu at position 6 on the $ chains creates a hydrophobic patch on the surface of deoxyhemoglobin S which is not properly positioned for aggregation in the oxygenated protein. 2. (3 points) Symptoms of individuals with the mutant hemoglobin in question 1 are likely to include: a. progressive loss of neuronal tissue in the central nervous system at an early age in indivudals homozygous for the mutant hemoglobin. B . collapse of the vertebrae in individuals homozygous for the mutant hemoglobin. c. unusually high resistance to bacterial infections in individuals homozygous for the mutant hemoglobin. d. an unusually severe course and persistence of malarial disease in individuals who are homozygous or heterozygous for the mutant hemoglobin. Sickling hemoglobins predispose to infarcts in the bones and the spleen, resulting in spinal deformities and increased susceptibility to infection. Nerve cells are not targeted. The sickled cells trap malarial parasites, clearing them effectively, and presumably conferring resistance to malaria. 3. (3 points) In the human neonate, a fraction of the hemoglobin is a form of fetal hemoglobin (Hb F: " 2 ( 2 ) in which the N-termini of all the polypeptide chains are blocked by acetylation and a number of amino acid substitutions result in four fewer positive charges lining the cavity between the ( chains. You would expect that: A . binding of 2,3-DPG to the low affinity quaternary conformation of this form of Hb F is diminished, resulting in increased oxygen affinity under physiological conditions. b. binding of 2,3-DPG to the high affinity quaternary conformation of this form of Hb F is diminished, resulting in decreased oxygen affinity under physiological conditions. c. diminished binding of 2,3-DPG to the tetramers of this form of Hb F results in an increased tendency of the protein to dissociate into "( dimers. d. the combination of modifications and substitutions locks this form of Hb F into the high affinity quaternary conformation. The presence of positive charges in the cavity formed between the deoxygenated $ chains accounts for binding of 2,3-DPG to the deoxy form of hemoglobin, thereby lowering oxygen affinity. Fetal hemoglobin cannot bind DPG as well, and therefore has a higher oxygen affinity than adult hemoglobin in the presence of 2,3-DPG. 4. (3 points) A preparation of normal adult hemoglobin (Hb A) has first been digested with
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SSimonPractice206[1] - _ Name and ID# (usually your Social...

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