Question 1

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

Accepted Answer

The decrease in hemoglobin's oxygen affinity at low pH, facilitating oxygen release in metabolically active tissues.

Question 2

What is the primary role of 2,3-bisphosphoglycerate (2,3-BPG) in red blood cells?

Accepted Answer

It stabilizes the T state of hemoglobin, promoting oxygen release.

Question 3

Which equation correctly represents the dissociation constant ($$K_d) $$for the binding of a ligand (L) to a protein (P)?

Accepted Answer

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

Question 4

A patient with chronic lung disease has elevated CO$$_2$$ levels in their blood. How does this affect hemoglobin's oxygen-binding affinity, and why?

Accepted Answer

Affinity decreases because CO$$_2$$ forms carbamates that stabilize the T state.

Question 5

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

Accepted Answer

Myoglobin has a higher affinity for oxygen than hemoglobin at low pO$$_2.$$

Question 6

During vigorous exercise, muscle tissues produce more H$$^+$$ and CO$$_2. $$What is the physiological consequence of this on oxygen delivery?

Accepted Answer

Hemoglobin releases more oxygen due to the Bohr effect and carbamate formation.

Question 7

Which amino acid residue in hemoglobin is protonated at low pH, leading to the formation of a salt bridge that stabilizes the T state?

Accepted Answer

Histidine 146

Question 8

A mutation in hemoglobin reduces its ability to bind 2,3-BPG. What is the most likely effect on the oxygen dissociation curve?

Accepted Answer

The curve shifts to the left, indicating increased oxygen affinity.

Question 9

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

Accepted Answer

HbF does not bind 2,3-BPG as effectively as HbA.

Question 10

Which of the following is a direct result of carbamate formation on hemoglobin?

Accepted Answer

Release of a proton, contributing to the Bohr effect.

Question 11

A patient is exposed to high altitude, resulting in increased 2,3-BPG production. What is the physiological significance of this adaptation?

Accepted Answer

It decreases hemoglobin's oxygen affinity, enhancing oxygen release to tissues.

Question 12

Which of the following best describes the role of carbonic anhydrase in red blood cells?

Accepted Answer

It catalyzes the conversion of CO$$_2 to $$bicarbonate, facilitating CO$$_2$$ transport.

Question 13

Which of the following is true regarding the oxygen-binding curve of hemoglobin?

Accepted Answer

It is sigmoidal, reflecting cooperative binding of oxygen.

Question 14

If the partial pressure of oxygen ($$pO_2) at $$which hemoglobin is 50% saturated is 26 mmHg, what does this value represent?

Accepted Answer

The $$K_d ($$dissociation constant) for oxygen binding to hemoglobin.

Question 15

Which of the following statements about the T (tense) and R (relaxed) states of hemoglobin is correct?

Accepted Answer

The T state is stabilized by salt bridges and 2,3-BPG.

Question 16

A person with a mutation that increases the positive charge in the central cavity of hemoglobin would most likely experience which of the following?

Accepted Answer

Decreased binding of 2,3-BPG and increased oxygen affinity.

Question 17

Which of the following best explains why myoglobin is more effective than hemoglobin at storing oxygen in muscle tissue?

Accepted Answer

Myoglobin has a higher oxygen affinity and is a monomer.

Question 18

Which of the following is a consequence of the formation of salt bridges between His146 and Asp94 in hemoglobin?

Accepted Answer

Stabilization of the T state and promotion of oxygen release.

Question 19

A patient is given a drug that increases the pH of their blood. What effect will this have on hemoglobin's oxygen affinity?

Accepted Answer

Oxygen affinity will increase, making it harder to release oxygen to tissues.

Protein Function: Oxygen-Binding Proteins (Hemoglobin and Myoglobin)

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