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7. 2,3-Bisphosphoglycerate (2,3-BPG) is an allosteric modifier that binds to the central cavity of hemoglobin. 2,3-BPG affects hemoglobin affinity for oxygen by binding at a site different than the oxygen binding site and promoting a shape change in the molecule. The result of 2,3-BPG binding is that oxygen binding curves shift right. When the small molecule is the same as the normal ligand for the protein this interaction is called homotropic as it is for oxygen and hemoglobin. The interaction of 2,3-BPG with hemoglobin is heterotropic since BPG and oxygen are not the same and do not bind to the same site. a) Define 2,3-BPG, cooperativity, oxygen affinity, and allosterism. How do all of these terms relate? b) The molecule 2,3-BPG binds to the deoxy form of hemoglobin in the central cavity. Explain why that makes sense for oxygen delivery and why BPG is said to stabilize the deoxy state. c) How do the levels of O2 in the atmosphere compare at sea level versus high altitude? Predict the blood levels of BPG for people who live at high altitudes, like Denver. How will those levels of BPG help their hemoglobin function better? d) In the mutant hemoglobin known as Hb Providence, an asparagine residue in the ?-chain replaces Lys82. In normal hemoglobin, Lys82 projects into the central cavity of the hemoglobin molecule. Predict the effect of the Lys ? Asn mutation on the affinity of allosteric modifiers (relative to normal Hb e.g. Hba) and describe the effect the mutation would have on the function (oxygen binding) of Hb Providence. e) Under appropriate conditions, hemoglobin dissociates into its four subunits. Isolated ? subunits bind oxygen, but the O2 saturation curve is hyperbolic instead of sigmoidal. In addition, the saturation curve is not affected by the presence of H+, CO2, or 2,3-BPG. What do these observations indicate about the cooperativity and allosterism observed in hemoglobin?

          7. 2,3-Bisphosphoglycerate (2,3-BPG) is an allosteric modifier that binds to the central cavity of hemoglobin. 2,3-BPG affects hemoglobin affinity for oxygen by binding at a site different than the oxygen binding site and promoting a shape change in the molecule. The result of 2,3-BPG binding is that oxygen binding curves shift right. When the small molecule is the same as the normal ligand for the protein this interaction is called homotropic as it is for oxygen and hemoglobin. The interaction of 2,3-BPG with hemoglobin is heterotropic since BPG and oxygen are not the same and do not bind to the same site.

a) Define 2,3-BPG, cooperativity, oxygen affinity, and allosterism. How do all of these terms relate?

b) The molecule 2,3-BPG binds to the deoxy form of hemoglobin in the central cavity. Explain why that makes sense for oxygen delivery and why BPG is said to stabilize the deoxy state.

c) How do the levels of O2 in the atmosphere compare at sea level versus high altitude? Predict the blood levels of BPG for people who live at high altitudes, like Denver. How will those levels of BPG help their hemoglobin function better?

d) In the mutant hemoglobin known as Hb Providence, an asparagine residue in the ?-chain replaces Lys82. In normal hemoglobin, Lys82 projects into the central cavity of the hemoglobin molecule. Predict the effect of the Lys ? Asn mutation on the affinity of allosteric modifiers (relative to normal Hb e.g. Hba) and describe the effect the mutation would have on the function (oxygen binding) of Hb Providence.

e) Under appropriate conditions, hemoglobin dissociates into its four subunits. Isolated ? subunits bind oxygen, but the O2 saturation curve is hyperbolic instead of sigmoidal. In addition, the saturation curve is not affected by the presence of H+, CO2, or 2,3-BPG. What do these observations indicate about the cooperativity and allosterism observed in hemoglobin?

7. 2,3-Bisphosphoglycerate (2,3-BPG) is an allosteric modifier that binds to the central cavity of hemoglobin. 2,3-BPG affects hemoglobin affinity for oxygen by binding at a site different than the oxygen binding site and promoting a shape change in the molecule. The result of 2,3-BPG binding is that oxygen binding curves shift right. When the small molecule is the same as the normal ligand for the protein this interaction is called homotropic as it is for oxygen and hemoglobin. The interaction of 2,3-BPG with hemoglobin is heterotropic since BPG and oxygen are not the same and do not bind to the same site.

a) Define 2,3-BPG, cooperativity, oxygen affinity, and allosterism. How do all of these terms relate?

b) The molecule 2,3-BPG binds to the deoxy form of hemoglobin in the central cavity. Explain why that makes sense for oxygen delivery and why BPG is said to stabilize the deoxy state.

c) How do the levels of O2 in the atmosphere compare at sea level versus high altitude? Predict the blood levels of BPG for people who live at high altitudes, like Denver. How will those levels of BPG help their hemoglobin function better?

d) In the mutant hemoglobin known as Hb Providence, an asparagine residue in the ?-chain replaces Lys82. In normal hemoglobin, Lys82 projects into the central cavity of the hemoglobin molecule. Predict the effect of the Lys ? Asn mutation on the affinity of allosteric modifiers (relative to normal Hb e.g. Hba) and describe the effect the mutation would have on the function (oxygen binding) of Hb Providence.

e) Under appropriate conditions, hemoglobin dissociates into its four subunits. Isolated ? subunits bind oxygen, but the O2 saturation curve is hyperbolic instead of sigmoidal. In addition, the saturation curve is not affected by the presence of H+, CO2, or 2,3-BPG. What do these observations indicate about the cooperativity and allosterism observed in hemoglobin?

Added by Janice S.

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