Question 1

Which of the following best describes the primary function of myoglobin in muscle tissue?

Accepted Answer

Stores oxygen for use during periods of high metabolic demand.

Question 2

Hemoglobin and myoglobin both contain a heme group. What is the role of the central Fe$$^{2+}$$ ion in the heme group?

Accepted Answer

It reversibly binds O$$_2$$ for storage or transport.

Question 3

Which of the following statements about the oxygen-binding curves of myoglobin and hemoglobin is correct?

Accepted Answer

Myoglobin displays a hyperbolic curve, while hemoglobin displays a sigmoidal curve due to cooperativity.

Question 4

What is the effect of carbon monoxide (CO) on hemoglobin's ability to transport oxygen?

Accepted Answer

CO binds to hemoglobin with much higher affinity than O$$_2$$, preventing oxygen binding and leading to poisoning.

Question 5

The equilibrium dissociation constant ($$K_d) $$for a protein-ligand interaction is defined as:

Accepted Answer

$$K_d = \frac{[P][L]}{[PL]}$$

Question 6

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

Accepted Answer

Hemoglobin exhibits cooperative binding, allowing it to release a large amount of oxygen in response to small decreases in pO$$_2.$$

Question 7

A patient is exposed to a low concentration of carbon monoxide. Which of the following best describes the effect on their hemoglobin?

Accepted Answer

Hemoglobin will bind CO preferentially, reducing oxygen transport and potentially causing hypoxia.

Question 8

The Hill coefficient ($$n) in $$the Hill equation for cooperative binding provides information about:

Accepted Answer

The degree of cooperativity in ligand binding.

Question 9

Which of the following is a correct statement about the Bohr effect in hemoglobin?

Accepted Answer

A decrease in pH decreases hemoglobin's affinity for oxygen, promoting oxygen release in tissues.

Question 10

Which of the following best describes the role of 2,3-bisphosphoglycerate (2,3-BPG) in oxygen transport?

Accepted Answer

2,3-BPG binds to hemoglobin and stabilizes the T-state, decreasing oxygen affinity and promoting oxygen release.

Question 11

A mutation in the beta chain of hemoglobin leads to the formation of hemoglobin S (HbS), which causes sickle cell anemia. What is the molecular basis for the sickling of red blood cells in this disease?

Accepted Answer

HbS forms aggregates due to exposed hydrophobic patches, distorting red blood cell shape.

Question 12

Which of the following equations correctly relates the fraction of occupied binding sites ($$Y) to $$ligand concentration ($$[L]) $$and the dissociation constant ($$K_d) $$for a simple protein-ligand interaction?

Accepted Answer

$$Y = \frac{[L]}{[L] + K_d}$$

Question 13

Which of the following is a function of globular proteins as described in the study materials?

Accepted Answer

Storage and transport of ions and molecules.

Question 14

If the $$K_d$$ for a protein-ligand interaction is $$1 \ \muM$$, what is the ligand concentration at which half of the protein binding sites are occupied?

Accepted Answer

$$1 \ \muM$$

Question 15

Which of the following best explains why myoglobin is not effective for oxygen transport in blood?

Accepted Answer

Myoglobin binds oxygen too tightly and does not release it efficiently at tissue pO$$_2.$$

Question 16

Which of the following statements about the heme group in hemoglobin is correct?

Accepted Answer

The central Fe$$^{2+}$$ ion in the heme group has six coordination sites.

Question 17

A patient at high altitude adapts by increasing the concentration of 2,3-BPG in their erythrocytes. What is the physiological consequence of this adaptation?

Accepted Answer

Increased 2,3-BPG decreases hemoglobin's oxygen affinity, promoting oxygen release in tissues.

Question 18

Which of the following best describes the structural change that occurs in hemoglobin upon oxygen binding?

Accepted Answer

The Fe$$^{2+}$$ ion moves into the plane of the porphyrin ring, triggering a transition from the T (tense) state to the R (relaxed) state.

Question 19

Which of the following is a correct statement about the relationship between $$K_d$$ and binding affinity?

Accepted Answer

A lower $$K_d$$ indicates stronger binding affinity.

Lecture 5: Globular Proteins: Structure, Function, and Oxygen Binding

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