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a) How much more O2 can be transported by the blood when erythrocytes leave the lungs? Consider that a normal adult has a concentration of 15 g hemoglobin/100 mL of blood and that the hemoglobin is 98% saturated with O2 at the usual pO2 of 100 torr in the lung at sea level. b) On the basis of the graph, explain how myoglobin facilitates the diffusion of O2 through muscle cells. Would myoglobin be effective as an O2-transport protein in cells of other tissues? Explain

a) How much more O2 can be transported by the blood when erythrocytes leave the lungs? Consider that a normal adult has a concentration of 15 g hemoglobin/100 mL of blood and that the hemoglobin is 98% saturated with O2 at the usual pO2 of 100 torr in the lung at sea level. b) On the basis of the graph, explain how myoglobin facilitates the diffusion of O2 through muscle cells. Would myoglobin be effective as an O2-transport protein in cells of other tissues? Explain

Biochemistry
Biochemistry
9th Edition
ISBN:9781319114671
Author:Lubert Stryer, Jeremy M. Berg, John L. Tymoczko, Gregory J. Gatto Jr.
Publisher:Lubert Stryer, Jeremy M. Berg, John L. Tymoczko, Gregory J. Gatto Jr.
Chapter1: Biochemistry: An Evolving Science
Section: Chapter Questions
Problem 1P
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a) How much more O2 can be transported by the blood when erythrocytes
leave the lungs? Consider that a normal adult has a concentration of 15 g hemoglobin/100 mL of blood
and that the hemoglobin is 98% saturated with O2 at the usual pO2 of 100 torr in the lung at sea level.

b) On the basis of the graph, explain how myoglobin facilitates the diffusion of O2 through muscle cells. Would myoglobin be effective as an O2-transport protein in cells of other tissues? Explain.

1. (a) The solubility of the dioxygen (O₂) molecule in blood at 37° C and ionic strength equivalent to 0.15 M NaCl is ~10-4 M. How much more O₂ can be transported by the blood when erythrocytes leave the lungs? Consider that a normal adult has a concentration of 15 g hemoglobin/100 mL of blood and that the hemoglobin is 98% saturated with O2 at the usual pO2 of 100 torr in the lung at sea level. 1.00 (b) The diagram to the right contrasts the oxygen binding curve of normal human hemoglobin (HbA) to that of myoglobin, a single polypeptide hemeprotein that serves as an oxygen storage protein in cardiac and skeletal mus- cle. The partial pressure of O2 (pO2) is given along the hor- izontal axis in units of torr (mm Hg) and is directly propor- tional to the concentration of dissolved oxygen in the solu- tion. The variable Yoz represents the fraction of heme sites Yo occupied by ligand. It is seen that the O2 dissociation curve for myoglobin is hyperbolic in shape while that of hemoglo- bin is sigmoidal. The two proteins exhibit high sequence identity and possess the same prosthetic group, iron-pro- tophyrin IX. The dashed curve is of a hypothetical mutant form of Hb with a p50 identical to that of normal HbA. In active muscle tissue the pO2 is approximately 10 torr at the cell surface but only 1 torr in mitochondria. Active mus- cle tissue consumes 0₂ much faster than other tissues. For myoglobin the pO2 at 50% saturation is 2.8 torr. On the ba- sis of the graph, explain how myoglobin facilitates the diffu- sion of O2 through muscle cells. Would myoglobin be effec- tive as an O2-transport protein in cells of other tissues? Ex- plain. 0.80 0.60 0.40 0.20 0.0 Myoglobin Venous pressure 20 40 Hemoglobin in whole blood Arterial pressure 60 p0₂ (tor) Comparison of oxygen dissociation curves for human hemoglobin (HbA) and myoglobin. The p50 of normal he- moglobin is 26 torr. That of myoglobin is 2.8 torr. 80 100 120
Transcribed Image Text:1. (a) The solubility of the dioxygen (O₂) molecule in blood at 37° C and ionic strength equivalent to 0.15 M NaCl is ~10-4 M. How much more O₂ can be transported by the blood when erythrocytes leave the lungs? Consider that a normal adult has a concentration of 15 g hemoglobin/100 mL of blood and that the hemoglobin is 98% saturated with O2 at the usual pO2 of 100 torr in the lung at sea level. 1.00 (b) The diagram to the right contrasts the oxygen binding curve of normal human hemoglobin (HbA) to that of myoglobin, a single polypeptide hemeprotein that serves as an oxygen storage protein in cardiac and skeletal mus- cle. The partial pressure of O2 (pO2) is given along the hor- izontal axis in units of torr (mm Hg) and is directly propor- tional to the concentration of dissolved oxygen in the solu- tion. The variable Yoz represents the fraction of heme sites Yo occupied by ligand. It is seen that the O2 dissociation curve for myoglobin is hyperbolic in shape while that of hemoglo- bin is sigmoidal. The two proteins exhibit high sequence identity and possess the same prosthetic group, iron-pro- tophyrin IX. The dashed curve is of a hypothetical mutant form of Hb with a p50 identical to that of normal HbA. In active muscle tissue the pO2 is approximately 10 torr at the cell surface but only 1 torr in mitochondria. Active mus- cle tissue consumes 0₂ much faster than other tissues. For myoglobin the pO2 at 50% saturation is 2.8 torr. On the ba- sis of the graph, explain how myoglobin facilitates the diffu- sion of O2 through muscle cells. Would myoglobin be effec- tive as an O2-transport protein in cells of other tissues? Ex- plain. 0.80 0.60 0.40 0.20 0.0 Myoglobin Venous pressure 20 40 Hemoglobin in whole blood Arterial pressure 60 p0₂ (tor) Comparison of oxygen dissociation curves for human hemoglobin (HbA) and myoglobin. The p50 of normal he- moglobin is 26 torr. That of myoglobin is 2.8 torr. 80 100 120
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