Question 1

Which of the following statements best describes a positive homotropic allosteric effector in hemoglobin?

Accepted Answer

It binds at the active site and increases the binding affinity of oxygen to other subunits.

Question 2

Which equation correctly represents the release of oxygen from hemoglobin in the presence of BPG, CO$$_2$$, and H$$^+$$?

Accepted Answer

$$\mathrm{Hb-(O_2$)_4 + BPG + CO_2$ + H^+ \rightleftharpoons Hb-BPG-CO_2$-H^+ + 4O_2}$$

Question 3

What is the effect of increased H$$^+$$ concentration (decreased pH) on hemoglobin's oxygen affinity?

Accepted Answer

It decreases hemoglobin's affinity for oxygen by favoring the T state.

Question 4

Which of the following is a negative heterotropic allosteric effector of hemoglobin?

Accepted Answer

2,3-bisphosphoglycerate (2,3-BPG)

Question 5

During hyperventilation, CO$$_2$$ levels in the blood decrease. What is the physiological consequence for oxygen delivery to tissues?

Accepted Answer

Oxygen delivery to tissues decreases due to stabilization of the R state.

Question 6

Which amino acid substitution in fetal hemoglobin reduces BPG binding affinity, resulting in higher O$$_2$$ affinity?

Accepted Answer

Serine at position 143

Question 7

The Bohr effect describes how changes in pH affect hemoglobin's oxygen binding. Which of the following best summarizes this effect?

Accepted Answer

As pH decreases, hemoglobin releases more oxygen.

Question 8

Which of the following is true regarding the T and R states of hemoglobin?

Accepted Answer

The R state has a higher affinity for oxygen than the T state.

Question 9

Which of the following best explains why sickle-cell disease provides a survival advantage in malaria-endemic regions?

Accepted Answer

Sickled erythrocytes block malaria parasite entry and reduce parasite survival.

Question 10

Which of the following blots is used to detect specific DNA sequences?

Accepted Answer

Southern blot

Question 11

What is the role of 2,3-bisphosphoglycerate (2,3-BPG) in hemoglobin function?

Accepted Answer

It decreases hemoglobin's affinity for oxygen by stabilizing the T state.

Question 12

Which of the following equations represents the formation of carbamate from hemoglobin and bicarbonate?

Accepted Answer

$$\mathrm{NH_2$ + $$HCO_3$$^- \rightarrow -N-COO^- + H^+ + H_2O}$$

Question 13

Which of the following statements about allosteric effectors is correct?

Accepted Answer

Heterotropic effectors bind at sites other than the active site.

Question 14

A patient is experiencing acidosis (low blood pH). What is the expected effect on hemoglobin's oxygen delivery?

Accepted Answer

Oxygen delivery to tissues will increase.

Question 15

Which of the following best describes the narrowing of the central channel in hemoglobin during the T to R transition?

Accepted Answer

It decreases the binding affinity for BPG.

Question 16

Which blotting technique is used to detect specific RNA sequences?

Accepted Answer

Northern blot

Question 17

Which of the following is a consequence of a mutation in the hemoglobin gene that is only present in somatic cells?

Accepted Answer

It will not be inherited by the next generation.

Question 18

Which of the following statements about evolutionary relationships among globins is correct?

Accepted Answer

A greater number of amino acid differences indicates a more ancient divergence.

Question 19

Which of the following is true regarding the inheritance pattern of sickle-cell disease?

Accepted Answer

Heterozygotes are usually asymptomatic except under oxygen stress.

Allosteric Regulation of Hemoglobin: Effectors, Mechanisms, and Clinical Relevance

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