3. (a) The (acid) Bohr effect is defined as the up- take of protons by hemoglobin molecules at pH ≤ 6.5 as O2 is dissociated from the protein in solution. Approxi- mately 0.6 mole protons are taken up for each mole of O2 released by normal human hemoglobin. The effect is seen as a "shift to the right" in the O2 dissociation curves with decrease in pH, indicating that the O2 binding affinity of Hb decreases at lower pH. On the right is a diagram compar- ing the pH dependence of the p50 values of Hb Deer Lodge [His(32)Arg] (filled symbols) and of HbA (---) in the absence of organic phosphates, i.e., "Stripped", and in the presence of saturating concentrations of IHP. On the basis of the definition of the Bohr effect given above, explain why the data in the diagram reflect the Bohr effect for the two types of human hemoglobins. log p50 1.5 1.0 0.5 0.0 -0.5 5 6 stripped 7 pH +DPG 8 IHP 9 (b) The Bohr effect is generally decreased in Hb Deer Louge compared to that in HbA. Provi an explanation why the decrease can be attributed to the presence of the His(32)Arg mutation. (c) Crocodiles are able to remain under water for up to 1 hour because, in contrast to human they can utilize virtually 100% of the oxygen in their blood. Humans can extract only about 66% of t oxygen from their blood, as shown by oxygen dissociation curves. In contrast to human deoxyHb, cro odile deoxyHb does not bind 2,3-bisphosphoglycerate. However, crocodile deoxyHb does bind t HCO3 anion. Explain the mechanism of the influence of the HCO3- ion and its metabolic origin.

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Chapter1: Biochemistry: An Evolving Science
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3. (a)
The (acid) Bohr effect is defined as the up-
take of protons by hemoglobin molecules at pH ≤ 6.5 as
O2 is dissociated from the protein in solution. Approxi-
mately 0.6 mole protons are taken up for each mole of O2
released by normal human hemoglobin. The effect is seen
as a "shift to the right" in the O2 dissociation curves with
decrease in pH, indicating that the O2 binding affinity of Hb
decreases at lower pH. On the right is a diagram compar-
ing the pH dependence of the p50 values of Hb Deer
Lodge [His(32)Arg] (filled symbols) and of HbA (- - -) in the
absence of organic phosphates, i.e., “Stripped”, and in the
presence of saturating concentrations of IHP.
On the basis of the definition of the Bohr effect given
above, explain why the data in the diagram reflect the Bohr
effect for the two types of human hemoglobins.
log p50
1.5
1.0
0.5
0.0
-0.5
5
6
stripped
7
pH
+DPG
8
IHP
9
(b) The Bohr effect is generally decreased in Hb Deer Louge compared to that in HbA. Provide
an explanation why the decrease can be attributed to the presence of the His(32)Arg mutation.
(c) Crocodiles are able to remain under water for up to 1 hour because, in contrast to humans,
they can utilize virtually 100% of the oxygen in their blood. Humans can extract only about 66% of the
oxygen from their blood, as shown by oxygen dissociation curves. In contrast to human deoxyHb, croc-
odile deoxyHb does not bind 2,3-bisphosphoglycerate. However, crocodile deoxyHb does bind the
HCO3 anion. Explain the mechanism of the influence of the HCO3- ion and its metabolic origin.
Transcribed Image Text:3. (a) The (acid) Bohr effect is defined as the up- take of protons by hemoglobin molecules at pH ≤ 6.5 as O2 is dissociated from the protein in solution. Approxi- mately 0.6 mole protons are taken up for each mole of O2 released by normal human hemoglobin. The effect is seen as a "shift to the right" in the O2 dissociation curves with decrease in pH, indicating that the O2 binding affinity of Hb decreases at lower pH. On the right is a diagram compar- ing the pH dependence of the p50 values of Hb Deer Lodge [His(32)Arg] (filled symbols) and of HbA (- - -) in the absence of organic phosphates, i.e., “Stripped”, and in the presence of saturating concentrations of IHP. On the basis of the definition of the Bohr effect given above, explain why the data in the diagram reflect the Bohr effect for the two types of human hemoglobins. log p50 1.5 1.0 0.5 0.0 -0.5 5 6 stripped 7 pH +DPG 8 IHP 9 (b) The Bohr effect is generally decreased in Hb Deer Louge compared to that in HbA. Provide an explanation why the decrease can be attributed to the presence of the His(32)Arg mutation. (c) Crocodiles are able to remain under water for up to 1 hour because, in contrast to humans, they can utilize virtually 100% of the oxygen in their blood. Humans can extract only about 66% of the oxygen from their blood, as shown by oxygen dissociation curves. In contrast to human deoxyHb, croc- odile deoxyHb does not bind 2,3-bisphosphoglycerate. However, crocodile deoxyHb does bind the HCO3 anion. Explain the mechanism of the influence of the HCO3- ion and its metabolic origin.
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