Question 1

Which of the following best describes the Bohr effect in hemoglobin?

Accepted Answer

The decrease in oxygen affinity of hemoglobin at low pH, facilitating oxygen release in tissues.

Question 2

Given the dissociation constant $$K_d$$ for a protein-ligand interaction, which of the following statements is correct?

Accepted Answer

$$K_d is $$inversely proportional to the affinity of the ligand for the protein.

Question 3

The Hill coefficient ($$n) is $$used to describe cooperativity in ligand binding. Which of the following statements is true?

Accepted Answer

A Hill coefficient of $$n \u003e 1$$ indicates positive cooperativity.

Question 4

Which of the following best explains the molecular basis for the allosteric regulation of hemoglobin by 2,3-BPG?

Accepted Answer

2,3-BPG binds to the central cavity of deoxyhemoglobin, stabilizing the T (tense) state and decreasing oxygen affinity.

Question 5

A patient with sickle cell disease has a mutation that substitutes valine for glutamic acid at position 6 of the beta-globin chain. What is the primary biochemical consequence of this mutation?

Accepted Answer

Formation of hemoglobin aggregates (fibers) under low oxygen conditions.

Question 6

Which of the following equations correctly represents the fractional saturation ($$Y) of a $$protein-ligand interaction?

Accepted Answer

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

Question 7

Which of the following statements about myoglobin and hemoglobin is correct?

Accepted Answer

Myoglobin exhibits a hyperbolic oxygen binding curve, while hemoglobin exhibits a sigmoidal curve due to cooperativity.

Question 8

Which of the following best describes the function of the distal histidine in hemoglobin?

Accepted Answer

It stabilizes the bound oxygen molecule and reduces the binding of carbon monoxide.

Question 9

A mutation in hemoglobin increases its affinity for oxygen. What is the most likely physiological consequence?

Accepted Answer

Reduced oxygen delivery to tissues due to decreased release of oxygen.

Question 10

Which of the following statements about gene families is correct?

Accepted Answer

Gene families arise from the process of gene duplication and subsequent functional specialization.

Question 11

Which of the following best explains why fetal hemoglobin (HbF) has a higher oxygen affinity than adult hemoglobin (HbA)?

Accepted Answer

HbF binds 2,3-BPG less strongly than HbA, resulting in higher oxygen affinity.

Question 12

Which of the following is the correct definition of $$P_{50} in $$the context of oxygen binding?

Accepted Answer

$$P_{50} is $$the partial pressure of oxygen at which hemoglobin is 50\% saturated.

Question 13

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

Accepted Answer

The $$eta$$ subunits rotate relative to the $$eta$$ subunits, causing a transition from the T (tense) to the R (relaxed) state.

Question 14

Which of the following is a direct consequence of the cooperative binding of oxygen to hemoglobin?

Accepted Answer

The oxygen binding curve of hemoglobin is sigmoidal.

Question 15

Which of the following best describes the role of the porphyrin (heme) prosthetic group in hemoglobin?

Accepted Answer

It is an organic molecule complexed with an iron atom that binds oxygen.

Question 16

Which of the following best explains why the oxygen binding curve of myoglobin is hyperbolic while that of hemoglobin is sigmoidal?

Accepted Answer

Myoglobin is a monomer and does not exhibit cooperativity, while hemoglobin is a tetramer and does.

Question 17

Which of the following statements about the Perutz mechanism of cooperativity in hemoglobin is correct?

Accepted Answer

Oxygen binding to one subunit increases the affinity of the remaining subunits for oxygen.

Question 18

Which of the following is a likely effect of increased chloride ion concentration on hemoglobin's oxygen affinity?

Accepted Answer

Increased chloride ion concentration decreases hemoglobin's oxygen affinity.

Question 19

Which of the following best describes an ancestral gene?

Accepted Answer

A gene that existed before duplication or divergent evolution and is presumed to have had sequence similarity to modern genes.

Hemoglobin, Myoglobin, and Allosteric Regulation: Study Notes

Guida di studio - Domande di pratica

Study guide - Flashcard