Question 1

Which of the following statements best explains why hemoglobin exhibits cooperative binding of oxygen, while myoglobin does not?

Accepted Answer

Hemoglobin has multiple subunits that interact, enabling conformational changes upon oxygen binding.

Question 2

Which equation correctly represents the equilibrium constant $$K_a$$ for the binding of a ligand (L) to a protein (P) to form a complex (PL)?

Accepted Answer

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

Question 3

A patient with sickle cell anemia has a mutation in the hemoglobin gene. Which amino acid substitution is responsible for this disease?

Accepted Answer

Glutamic acid to valine

Question 4

2,3-Bisphosphoglycerate (2,3-BPG) is a negative allosteric modulator of hemoglobin. What is the effect of increased 2,3-BPG concentration on hemoglobin's oxygen affinity?

Accepted Answer

It decreases hemoglobin's affinity for oxygen.

Question 5

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

Accepted Answer

Hemoglobin releases oxygen more readily at low pH.

Question 6

A ligand binds to a protein with $$K_a = 50 	ext{ mM}^{-1}. If $$the ligand concentration is $$[L] = 0.3 	ext{ mM}$$, what fraction of the binding sites are occupied? Use $$Y = \frac{K_a[L]}{1 + K_a[L]}.$$

Accepted Answer

$$Y = 0.94$$

Question 7

Which statement about fetal hemoglobin (HbF) compared to adult hemoglobin (HbA) is correct?

Accepted Answer

HbF has a higher affinity for oxygen than HbA.

Question 8

Which of the following is a consequence of carbon monoxide (CO) binding to hemoglobin?

Accepted Answer

CO increases hemoglobin's affinity for oxygen, but prevents oxygen release to tissues.

Question 9

Which of the following best describes the quaternary structure of hemoglobin?

Accepted Answer

It is a tetramer composed of two alpha and two beta subunits.

Question 10

During intense exercise at high altitude, which factor most contributes to increased oxygen delivery to tissues?

Accepted Answer

Increased 2,3-BPG concentration in red blood cells

Question 11

Which of the following is true regarding the effect of pH on oxygen binding to hemoglobin in the lungs?

Accepted Answer

Higher pH in the lungs increases hemoglobin's affinity for oxygen.

Question 12

A mutation replaces a glutamic acid with a valine in the beta chain of hemoglobin. What is the most likely consequence?

Accepted Answer

Formation of hydrophobic patches leading to sickle-shaped red blood cells

Question 13

Which of the following best explains why athletes often train at high altitude?

Accepted Answer

High altitude increases 2,3-BPG, which decreases hemoglobin's oxygen affinity and enhances oxygen delivery to tissues.

Question 14

Which of the following is a direct effect of the Bohr equation $$	ext{CO}_2 + 	ext{H}_2	ext{O} \leftrightarrow 	ext{H}_2	ext{CO}_3 \leftrightarrow 	ext{H}^+ + 	ext{HCO}_3^- on $$hemoglobin function?

Accepted Answer

Increased $$	ext{CO}_2$$ leads to lower pH, promoting oxygen release from hemoglobin.

Question 15

If 75% of the binding sites on a protein are occupied by ligand, and $$K_a = 50 	ext{ mM}^{-1}$$, what is the ligand concentration $$[L]$$? Use $$Y = \frac{K_a[L]}{1 + K_a[L]}.$$

Accepted Answer

$$[L] = 0.03 	ext{ mM}$$

Question 16

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

Accepted Answer

2,3-BPG binds to the deoxygenated form of hemoglobin, stabilizing it and promoting oxygen release.

Question 17

Which of the following is a reason why myoglobin is not an effective oxygen transporter in blood?

Accepted Answer

Myoglobin binds oxygen too tightly and does not release it efficiently to tissues.

Question 18

Which of the following best describes the effect of a Glu to Val substitution in hemoglobin compared to a Glu to Lys substitution?

Accepted Answer

Glu to Val creates a hydrophobic patch, leading to sickle cell anemia; Glu to Lys does not.

Question 19

Which of the following is true regarding the oxygen dissociation curve of hemoglobin?

Accepted Answer

It is sigmoidal, indicating cooperative binding.

Protein Function: Hemoglobin – Structure, Binding, and Modulation

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