Question 1

Which of the following best explains why hemoglobin is considered an allosteric protein?

Accepted Answer

It undergoes conformational changes upon ligand binding that affect the affinity of other binding sites.

Question 2

What is the primary physiological role of myoglobin in muscle tissue?

Accepted Answer

To store oxygen for use during periods of high metabolic demand.

Question 3

Which statement accurately describes the heme group in hemoglobin?

Accepted Answer

It is a prosthetic group with a central iron ion in the ferrous (Fe2+) state bound to protoporphyrin.

Question 4

Upon oxygen binding, what structural change occurs in the heme group of hemoglobin?

Accepted Answer

The iron ion moves into the plane of the porphyrin ring.

Question 5

Which of the following best describes the effect of carbon monoxide (CO) on hemoglobin function?

Accepted Answer

CO binds to the heme group with much higher affinity than O2, blocking oxygen binding and transport.

Question 6

Which of the following is true regarding the quaternary structure of adult hemoglobin (HbA)?

Accepted Answer

It is a tetramer composed of two alpha and two beta chains ($$\$$alpha_2$$\$$beta_2$$).

Question 7

Which of the following best explains the sigmoidal shape of the hemoglobin oxygen-binding curve?

Accepted Answer

Hemoglobin exhibits cooperative binding, where binding of one O2 increases the affinity for subsequent O2 molecules.

Question 8

Which of the following molecules binds to hemoglobin and stabilizes the T (tense) state, thereby promoting oxygen release in tissues?

Accepted Answer

2,3-bisphosphoglycerate (2,3-BPG)

Question 9

The Bohr effect describes the influence of which factors on hemoglobin’s affinity for oxygen?

Accepted Answer

pH and carbon dioxide concentration

Question 10

Which of the following equations represents the reaction catalyzed by carbonic anhydrase in red blood cells?

Accepted Answer

$$\mathrm{CO_2 + H_2O \rightarrow HCO_3^- + H^+}$$

Question 11

Which of the following statements best describes the relationship between myoglobin and the subunits of hemoglobin?

Accepted Answer

They have very similar tertiary structures, but different primary structures.

Question 12

A patient is exposed to high levels of carbon monoxide. Which of the following best describes the effect on oxygen delivery to tissues?

Accepted Answer

Oxygen delivery decreases because CO occupies the heme sites, preventing O2 binding.

Question 13

Which of the following best explains why hemoglobin is more efficient than myoglobin at delivering oxygen from the lungs to tissues?

Accepted Answer

Hemoglobin exhibits cooperative binding, allowing it to release more oxygen in tissues where $$pO_2 is $$low.

Question 14

Which of the following changes occurs when hemoglobin transitions from the T state to the R state?

Accepted Answer

The subunits rotate approximately 15 degrees relative to each other.

Question 15

Which of the following best describes the effect of decreasing blood pH on hemoglobin’s oxygen-binding affinity?

Accepted Answer

Affinity decreases, promoting oxygen release in tissues.

Question 16

Which of the following statements about 2,3-bisphosphoglycerate (2,3-BPG) is correct?

Accepted Answer

2,3-BPG binds to the central cavity of deoxyhemoglobin and decreases oxygen affinity.

Question 17

A mutation causes hemoglobin to have a higher affinity for oxygen and a left-shifted oxygen-binding curve. What is a likely physiological consequence?

Accepted Answer

Decreased oxygen delivery to tissues due to reduced release.

Question 18

Which of the following best describes the role of the proximal histidine in hemoglobin?

Accepted Answer

It coordinates the iron ion in the heme group.

Question 19

Which of the following is a direct effect of CO2 binding to hemoglobin?

Accepted Answer

CO2 binds to the N-terminal amino groups, stabilizing the T state and promoting oxygen release.

Question 20

Which of the following best explains why oxygen is poorly soluble in water and requires transport proteins like hemoglobin?

Accepted Answer

Oxygen is a small, nonpolar molecule with low solubility in aqueous environments.

Protein Binding, Molecular Recognition, and Allostery: Hemoglobin and Myoglobin

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