Question 1

Which of the following best explains why hemoglobin (Hb) is more effective than myoglobin (Mb) at transporting oxygen from the lungs to tissues in mammals?

Accepted Answer

Hemoglobin can switch between high and low affinity states due to cooperative binding, allowing efficient oxygen loading in the lungs and unloading in tissues.

Question 2

Given the binding curve equation for myoglobin: $$	heta = \frac{pO_2$}{pO_2$ + P_{50}}$$, what does $$P_{50}$$ represent?

Accepted Answer

The partial pressure of O$$_2 at $$which 50% of myoglobin is saturated.

Question 3

A protein has a $$K_D of 5 nM $$for its ligand, while another has a $$K_D of 30 nM $$for the same ligand. Which statement is correct?

Accepted Answer

The protein with $$K_D = 5 nM $$has a higher affinity for the ligand.

Question 4

Which of the following is a key assumption of the law of mass action for ligand binding that is violated by hemoglobin's cooperative binding?

Accepted Answer

Binding does not alter the receptor; ligands bind independently.

Question 5

The Hill equation for cooperative binding is $$	heta = \frac{[L]^n}{K_D + [L]^n}. $$What does the Hill coefficient $$n \u003e 1$$ indicate?

Accepted Answer

Positive cooperativity.

Question 6

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

Accepted Answer

Hemoglobin releases more O$$_2 at $$lower pH, facilitating oxygen delivery to metabolically active tissues.

Question 7

Which model of allostery assumes that all subunits of a protein switch between conformations simultaneously?

Accepted Answer

Symmetry (MWC) model.

Question 8

In the context of protein-ligand binding, what does a low $$K_D$$ value indicate?

Accepted Answer

High affinity between protein and ligand.

Question 9

A patient with lactic acidosis (low blood pH) is experiencing hypoxia. According to the Bohr effect, what will happen to the oxygen delivery by hemoglobin?

Accepted Answer

Hemoglobin will release more oxygen to the tissues, increasing oxygen delivery.

Question 10

Which of the following statements about the induced-fit model of protein-ligand interaction is correct?

Accepted Answer

Ligand binding induces a conformational change in the protein, optimizing the interaction.

Question 11

Given the Hill plot equation $$\log\left(\frac{	heta}{1-	heta}ight) = n\log[L] - \log K_D$$, what does the slope of the linear region represent?

Accepted Answer

The Hill coefficient, indicating the degree of cooperativity.

Question 12

Which structural feature allows hemoglobin to exhibit cooperative binding?

Accepted Answer

It has multiple subunits that can communicate conformational changes.

Question 13

If the partial pressure of O$$_2 in $$the lungs is 85 mmHg and in the capillaries is 25 mmHg, and hemoglobin has a Hill coefficient of 3.2 and $$P_{50} of 31 $$mmHg, what is the change in fractional O$$_2$$ saturation ($$\Delta	heta) $$from lungs to capillaries?

Accepted Answer

$$\Delta	heta = -0.63$$

Question 14

Which of the following best describes the role of the distal histidine in the heme pocket of myoglobin and hemoglobin?

Accepted Answer

It forms a hydrogen bond with bound O$$_2$$, increasing O$$_2$$ selectivity over CO.

Question 15

Which of the following is true regarding the T (tense) and R (relaxed) states of hemoglobin?

Accepted Answer

The T state is stabilized by salt bridges and has lower affinity for oxygen.

Question 16

Which of the following equations correctly relates the equilibrium dissociation constant $$K_D to $$the rate constants for association ($$k_{on}) $$and dissociation ($$k_{off}$$)?

Accepted Answer

$$K_D = k_{off}/k_{on}$$

Question 17

Which of the following best describes allosteric regulation in hemoglobin?

Accepted Answer

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

Question 18

Which of the following is a real-world consequence of the Bohr effect during intense exercise?

Accepted Answer

Hemoglobin releases more oxygen to muscles due to lower pH from lactic acid production.

Protein Function: Oxygen Binding and Allostery in Hemoglobin and Myoglobin

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