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Which of the following is false?

a. The release of oxygen from the R form of hemoglobin in red blood cells is more pronounced than in pure hemoglobin as the concentration of oxygen decreases.

b. In the presence of 2,3-bisphosphoglycerate, the affinity for oxygen in fetal hemoglobin is higher than maternal hemoglobin

c. Myoglobin does not use an allosteric effect

d. Hydrogen ions and carbon dioxide will help increase the release of oxygen from the R form of hemoglobin in the tissue.

e. None of the above

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Related questions

Match the words (A-E) with the statements below: ( 10 pts)

A. Bohr

B. 2, 3-BPG

C. Carbamate

D. Carbon dioxide

E. Concerted

F. Distal Histidine

G. Heme

H. Hemoglobin

I. Myoglobin

J. Sickle Cell Anemia

This has the ability to protect against carbon monoxide binding to the heme _______________

This is the molecule whose function is to facilitate diffusion of oxygen in muscle cells. ___________

The ability of myoglobin to bind oxygen depends on the presence of a bound prosthetic group called .

The shape of this protein has a sigmoidal curve _______________

As the partial pressure of ___________ increases, the affinity of oxygen binding to hemoglobin decreases. (there can be two answers)

The effect of hydrogen ions and carbon dioxide on the binding of oxygen to hemoglobin is called the _____________ effect

___________ is an allosteric effector that binds to the positive charges on the hemoglobin molecule .

Hemoglobin binding of oxygen is best described as a combination of sequential and ______________ model.

Carbon dioxide forms ______________ groups in proteins by reaction with N-terminal groups.

This condition is a result of a single-point mutation in the β chain of hemoglobin:__________________

1. The dominant motif found in hemoglobin and myoglobin is: a) twisted beta sheet b) beta barrel c) helix-loop-helix d) 7-TM 2. Myoglobin has how many polypeptide chains? A) 1 b) 2 c) 3 d) 4 3. Structurally and functionally, hemoglobin closely resembles a(n) a) transmembrane protein b) mucopolysaccharide c) bile salt d) allosteric enzyme 4. The oxygen binding site in hemoglobin and myoglobin is called: a) BPG b) heme c) proximal-His d) N-terminal carbamate 5. The proximal His residue in hemoglobin and myoglobin binds to which atom or molecule? A) CO2 b) O2 c) Fe d) BPG 6. The distal His residue in hemoglobin and myoglobin binds to which atom or molecule? A) CO2 b) O2 c) Fe d) BPG 7. BPG binds to: a) N-terminal carbamate b) proximal His c) heme group d) central cavity 8. Indirect activity of CO2 is a result of increased concentration of which chemical species? A) BPG b) H+ c) heme iron d) distal His 9. Direct activity of CO2 is a result of binding to which molecular feature? A) the heme group b) the N-terminal ends of the 4 polypeptide chains c) the central cavity d) the proximal His 10. The sigmoidal, cooperative binding curve commonly observed for hemoglobin is a result of: a) competition between CO2 and O2 for heme binding. B) competition between heme and distal His for O2 binding c) competition between BPG and CO2 for binding at the central cavity site d) T to R transition 11. Hemoglobin has a tendency to release its oxygen to the tissues because: a) in this region pH is high and O2 concentrations are low b) in this region both pH and O2 concentrations are low c) in this region both pH and O2 concentrations are high d) there is much BPG in this region 12. Which statement about fetal hemoglobin is not true? A) fetal hemoglobin has gamma chains instead of beta chains b) fetal hemoglobin binds BPG less strongly than maternal hemoglobin c) fetal hemoglobin binds oxygen less strongly than maternal hemoglobin d) fetal hemoglobin binds oxygen more strongly than maternal hemoglobin 13. Which process is most responsible for the sickling of cells seen in sickle cell disease? A) aggregation of the oxygenated R form of hemoglobin-S to form insoluble fibers b) aggregation of the deoxygenated T form of hemoglobin-S to form insoluble fibers c) Hemoglobin-S does not contain heme d) Hemoglobin-S contains a mutant form of heme which will not bind oxygen 14. A person with sickle-cell trait is very unlikely to catch which disease? A) malaria b) colon cancer c) avian flu d) whooping cough 15. A person with a genetic defect which results in the synthesis of an insufficient amount of the alpha chain of hemoglobin is said to have which disease? A) alpha thalassemia b) beta thalassemia c) pernicious anemia d) Crohn’s disease

Normal adult hemoglobin is called Hemoglobin A (Hb A). Ninety-eight percent of adult hemoglobin is Hb A and 2% is Hb A2. There are other forms of hemoglobin. For example, the developing fetus has a different kind of hemoglobin than most normal adults. Fetal hemoglobin (Hb F) is synthesized beginning at the third month of gestation and continues up through birth. After the neonate is born, hemoglobin F synthesis declines (because synthesis of the (chain declines) and hemoglobin A is synthesized. By the time the baby is six months old, 98% of its hemoglobin is Hemoglobin A. There is also a mutant form of hemoglobin called Hemoglobin S, which is found in persons with the disease sickle cell anemia. The disease sickle cell anemia is one of the major health problems facing the African-American community. The World Health Organization estimates that 250,000 babies world wide are born with sickle cell anemia. Currently there is no cure. A person afflicted with sickle cell anemia has inherited a defective gene from each parent. The defective gene is the one coding for the β-chain. The amino acid at position 6 on each β chain has been mutated from a glutamate to a valine. Normal α chains have a decreased affinity for the mutated β chains; thus assembly of the HbS tetramer is more difficult. Red blood cells containing HbS form a sickle shape because the Hb S molecules polymerize. Hb S molecules are more likely to polymerize when in the deoxygenated T form than in the oxygenated R form. The polymerized Hb deforms the normal discoid shape of the red blood cells, producing a sickle-shaped cell. The sickle shaped red blood cells become trapped in capillaries and organs, depriving the victim of adequate oxygen supply and causing chronic pain and organ damage.

Glover, R. E., Ivy, E. D., Orringer, E. P., Maeda, H., and Mason, R. (1999) Molecular Pharmacology 55, pp. 1006-1010.

Huang, J., Hadimani, S. B., Rupon, J. W., Ballas, S. K., Kim-Shapiro, D. B., and S. Bruce King (2002) Biochemistry 41, pp. 2466-2474.

S. Bruce King (2003) J.Clin. Invest., 111, pp. 171-172.

1) Why do you think Hb S has higher tendency to polymerize compared to Hb A?

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