Question 1

Why is it advantageous for hemoglobin to have allosteric properties?

Accepted Answer

Hemoglobin binds oxygen in a positive cooperative manner.This allows it to become saturated in the lungs,where oxygen pressure is high.When the hemoglobin moves to tissues,the lower oxygen pressure induces it to release oxygen and thus deliver oxygen where it is needed.

Question 2

Which is NOT correct concerning the accepted models that describe cooperative binding?

Accepted Answer

A)   In the sequential model, the binding of a ligand changes the conformation of the subunit to which it binds, in turn inducing a change in neighboring subunits.
B)   All known allosteric proteins exhibit either the concerted or sequential model exclusive of the other.
C)   Both models incorporate a low affinity T-state and a higher affinity R-state.
D)   Both models explain the sigmoid-shaped binding curve.
E)   In the concerted model, all molecules exist either in the T-state or the R-state. B

Question 3

Which of the following is a genetic disease that results from a decreased production of one of the subunits of hemoglobin?

Accepted Answer

A)   thalassemia
B)   pernicious anemia
C)   megaloblastic hereditary anemia
D)   acanthocytosis
E)   aplastic anemia A

Question 4

In normal adult hemoglobin,HbA,the β6 position is a glutamate residue,whereas in sickle-cell hemoglobin,HbS,it is a ____________ residue.

Accepted Answer

The answer of In normal adult hemoglobin,HbA,the β6 position is...

Question 5

What oxidized heme protein does not reversibly bind oxygen?

Accepted Answer

A)   metmyoglobin
B)   oxyhemoglobin
C)   carboxyhemoglobin
D)   leghemoglobin
E)   None of the answers is correct.

Question 6

What is formed when carbon dioxide reacts with the amino terminal group of deoxyhemoglobin?

Accepted Answer

A)   amide
B)   imine
C)   carbonate
D)   carbamate
E)   None of the answers is correct.

Question 7

What is metmyoglobin?

Accepted Answer

The answer of What is metmyoglobin?...

Question 8

What is the composition of fetal hemoglobin?

Accepted Answer

A)   two   α\alphaα  chains and two  β\betaβ  chains.
B)   two   α\alphaα  chains and two  γ\gammaγ  chains.
C)   two   α\alphaα  chains and two  β\betaβ  chains
D)   two  α\alphaα  chains and two  δ\deltaδ  chains
E)   four  β\betaβ  chains

Question 9

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

Accepted Answer

The answer of The ability of myoglobin to bind oxygen...

Question 10

Another reason why hemoglobin is sensitive to changes in pH is that the T-state of hemoglobin is stabilized by a salt bridge between β₁ Asp 94 and the C-terminal ___________________ of the β1 chain.

Accepted Answer

The answer of Another reason why hemoglobin is sensitive to...

Question 11

What functional role does the "distal histidine" play in the function of myoglobin and hemoglobin?

Accepted Answer

The answer of What functional role does the "distal histidine"...

Question 12

Describe the structure of normal adult hemoglobin.

Accepted Answer

The answer of Describe the structure of normal adult hemoglobin....

Question 13

Which of the following is correct concerning fetal hemoglobin?

Accepted Answer

A)   Fetal hemoglobin is composed of two α and two γ subunits.
B)   Fetal hemoglobin binds 2,3-BPG more tightly than normal adult hemoglobin.
C)   Fetal hemoglobin binds oxygen less than HbA at all pO2.
D)   Fetal hemoglobin does not exist in the T-form.
E)   None of the answers is correct.

Question 14

Which of the following represents the most predominant form for the transfer of carbon dioxide in the blood?

Accepted Answer

A)   CO2
B)   H2CO3
C)   HCO3-
D)   CO32-
E)   None of the answers is correct.

Question 15

Hemoglobin-binding of oxygen is best described as a

Accepted Answer

A)   concerted model.
B)   Michaelis-Menten model.
C)   sequential model.
D)   combination of sequential and concerted models.
E)   None of the answers is correct.

Question 16

Sickle-cell anemia is caused by

Accepted Answer

A)   a decreased production of α chains of hemoglobin.
B)   a substitution of a Glu residue for a Phe residue at the β6 position.
C)   the loss of the heme group because the proximal His is oxidized.
D)   a substitution of a Val residue for a Glu residue at the β6 position.
E)   a substitution of Glu residue for His at the C-terminal of the α chain.

Question 17

Describe the chemical basis of the Bohr effect.

Accepted Answer

The answer of Describe the chemical basis of the Bohr...

Question 18

Which of the following is correct concerning the oxygenation plot of proteins X and Y shown below?

Accepted Answer

A)   Protein Y exhibits tighter oxygen binding than protein X.
B)   Protein Y would function as a better oxygen-transport protein than protein X.
C)   Protein X exhibits cooperative binding, whereas Y does not.
D)   Protein Y corresponds to myoglobin, and protein X corresponds to hemoglobin.
E)   Protein X contains multiple binding sites.

Question 19

Which of the following is correct concerning the oxygenation plot of proteins X and Y shown below?

Accepted Answer

A)   Protein Y exhibits tighter oxygen-binding than protein X.
B)   Protein Y corresponds to fetal hemoglobin, and protein X corresponds to normal adult hemoglobin.
C)   Protein X corresponds to fetal hemoglobin, and protein Y corresponds to normal adult hemoglobin.
D)   Protein X corresponds to myoglobin, and protein Y corresponds to hemoglobin.
E)   None of the answers is correct.

Question 20

Which of the following is the immediate product of the reaction between carbon dioxide and water?

Accepted Answer

A)   HCO2H
B)   HCO3-
C)   CO32-
D)   H2CO3-
E)   None of the answers is correct.

Exam 7: Hemoglobin: a Portrait of a Protein in Action

Why is it advantageous for hemoglobin to have allosteric properties?

Which is NOT correct concerning the accepted models that describe cooperative binding?

Which of the following is a genetic disease that results from a decreased production of one of the subunits of hemoglobin?

In normal adult hemoglobin,HbA,the β6 position is a glutamate residue,whereas in sickle-cell hemoglobin,HbS,it is a ____________ residue.

What oxidized heme protein does not reversibly bind oxygen?

What is formed when carbon dioxide reacts with the amino terminal group of deoxyhemoglobin?

What is metmyoglobin?

What is the composition of fetal hemoglobin?

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

Another reason why hemoglobin is sensitive to changes in pH is that the T-state of hemoglobin is stabilized by a salt bridge between β1 Asp 94 and the C-terminal ___________________ of the β1 chain.

What functional role does the "distal histidine" play in the function of myoglobin and hemoglobin?

Describe the structure of normal adult hemoglobin.

Which of the following is correct concerning fetal hemoglobin?

Which of the following represents the most predominant form for the transfer of carbon dioxide in the blood?

Hemoglobin-binding of oxygen is best described as a

Sickle-cell anemia is caused by

Describe the chemical basis of the Bohr effect.

Which of the following is correct concerning the oxygenation plot of proteins X and Y shown below?

Which of the following is correct concerning the oxygenation plot of proteins X and Y shown below?

Which of the following is the immediate product of the reaction between carbon dioxide and water?

Another reason why hemoglobin is sensitive to changes in pH is that the T-state of hemoglobin is stabilized by a salt bridge between β₁ Asp 94 and the C-terminal ___________________ of the β1 chain.