Question 1

Which of the following best describes the role of a ligand in protein binding?

Accepted Answer

A ligand binds to a protein through non-covalent interactions, and this binding is reversible.

Question 2

Given the equilibrium $$P + L \rightleftharpoons PL$$, which equation correctly represents the dissociation constant $$K_d$$?

Accepted Answer

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

Question 3

If the affinity of a protein for its ligand increases, what happens to the dissociation constant $$K_d$$?

Accepted Answer

$$K_d$$ decreases

Question 4

Which of the following statements about induced fit is correct?

Accepted Answer

Induced fit increases ligand specificity by allowing the protein to adapt its shape to the ligand.

Question 5

The fraction of protein binding sites occupied by ligand ($$Y) is $$given by $$Y = \dfrac{[L]}{[L] + K_d}. $$What is the value of $$Y$$ when $$[L] = K_d$$?

Accepted Answer

$$Y = 0.5$$

Question 6

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

Accepted Answer

Hemoglobin has multiple subunits that allow conformational changes to be transmitted between them.

Question 7

What is the physiological significance of the Bohr Effect in hemoglobin?

Accepted Answer

It enables hemoglobin to deliver more oxygen to tissues that are actively metabolizing and producing high levels of CO$$_2.$$

Question 8

Which of the following is true regarding the effect of 2,3-BPG on hemoglobin?

Accepted Answer

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

Question 9

A patient is experiencing acidosis (low blood pH). What effect does this have on hemoglobin's ability to bind oxygen?

Accepted Answer

Acidosis decreases hemoglobin's affinity for oxygen, promoting oxygen release to tissues.

Question 10

Given the Henderson-Hasselbalch equation $$\mathrm{pH} = \mathrm{p}K_a + \log \left( \dfrac{[\mathrm{HCO}_3^-]}{[\mathrm{H}_2\mathrm{CO}_3]} \right)$$, calculate the pH of blood serum if $$[\mathrm{HCO}_3^-] = 0.24 M$$, $$[\mathrm{H}_2\mathrm{CO}_3] = 0.024 M$, \mathrm{p}K_a = 6.1.$$

Accepted Answer

$$\mathrm{pH} = 7.37$$

Question 11

Which of the following best describes the role of His HC3 in hemoglobin?

Accepted Answer

His HC3 forms a salt bridge that stabilizes the T-state of deoxyhemoglobin.

Question 12

What happens to the pK$$_a of $$His HC3 in deoxyhemoglobin compared to its free amino acid form?

Accepted Answer

The pK$$_a$$ increases due to stabilization by a salt bridge.

Question 13

Why does carbon monoxide (CO) bind more tightly to hemoglobin than oxygen?

Accepted Answer

CO binds to the iron in heme with a higher affinity due to its linear geometry.

Question 14

Which of the following is a consequence of the Bohr Effect during exercise?

Accepted Answer

Hemoglobin releases more oxygen in tissues with high CO$$_2$$ and low pH.

Question 15

What is the effect of 2,3-BPG concentration on oxygen delivery at high altitude?

Accepted Answer

2,3-BPG concentration increases, promoting oxygen release to tissues.

Question 16

Which statement best explains why the oxygen binding curve for hemoglobin is sigmoidal?

Accepted Answer

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

Question 17

Which of the following is an example of an allosteric effector of hemoglobin?

Accepted Answer

2,3-BPG

Question 18

If a patient hyperventilates, what happens to the pH of their blood and why?

Accepted Answer

pH increases due to decreased CO$$_2$$ concentration.

Question 19

Which of the following best describes the function of the prosthetic group in hemoglobin?

Accepted Answer

It binds oxygen reversibly and is required for protein function.

Protein-Ligand Binding and Hemoglobin Function: Biochemistry Study Notes

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