Q: Which equation correctly describes the fraction saturation ($$\theta) of $$myoglobin with oxygen at a given partial pressure $$pO_2$$?

$$\theta = \dfrac{[pO_2$]}{[pO_2$] + P_{50}}$$

Question 1

Which of the following best explains why myoglobin is nearly saturated with oxygen in both the lungs and peripheral tissues?

Accepted Answer

Myoglobin has a high affinity for oxygen, resulting in a hyperbolic oxygen-saturation curve and near-complete saturation at physiological oxygen pressures.

Question 2

Hemoglobin displays a sigmoidal oxygen binding curve due to which property?

Accepted Answer

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

Question 3

Which equation correctly describes the fraction saturation ($$	heta) of $$myoglobin with oxygen at a given partial pressure $$pO_2$$?

Accepted Answer

$$	heta = \dfrac{[pO_2$]}{[pO_2$] + P_{50}}$$

Question 4

A patient is exposed to carbon monoxide (CO). Which statement best explains the molecular basis of CO poisoning?

Accepted Answer

CO binds to the heme iron with much higher affinity than oxygen, displacing oxygen and preventing its transport.

Question 5

Which of the following is a direct consequence of the Bohr effect in active muscle tissue?

Accepted Answer

Hemoglobin's affinity for oxygen decreases due to lower pH, promoting oxygen release.

Question 6

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

Accepted Answer

2,3-BPG binds to deoxyhemoglobin, stabilizing the T state and decreasing hemoglobin's affinity for oxygen.

Question 7

At high altitude, the body adapts by increasing the concentration of 2,3-BPG. What is the physiological consequence of this adaptation?

Accepted Answer

Hemoglobin's affinity for oxygen decreases, facilitating oxygen release to peripheral tissues.

Question 8

Which structural difference between fetal hemoglobin (HbF) and adult hemoglobin (HbA) accounts for HbF's higher oxygen affinity?

Accepted Answer

HbF has fewer positively charged residues at the 2,3-BPG binding site, reducing its affinity for 2,3-BPG and increasing oxygen affinity.

Question 9

Which of the following best describes the molecular basis of sickle cell anemia?

Accepted Answer

A single amino acid substitution (Glu6Val) in the beta chain of hemoglobin, causing deoxy HbS to aggregate and deform red blood cells.

Question 10

Why are individuals heterozygous for sickle cell anemia more resistant to malaria?

Accepted Answer

Deformed red blood cells containing malaria parasites are selectively destroyed by the spleen due to sickling under low oxygen and low pH conditions.

Question 11

Which of the following is NOT a function of the heme group in myoglobin and hemoglobin?

Accepted Answer

Catalyzing the conversion of CO$$_2 to $$bicarbonate.

Question 12

Which of the following equations represents the conversion of CO$$_2 to $$bicarbonate in red blood cells?

Accepted Answer

$$CO_2 + H_2O$$ \rightarrow H_2CO_3 \rightarrow $$HCO_3^- + H$$^+$$

Question 13

Which statement best describes the role of allosteric effectors in hemoglobin function?

Accepted Answer

Allosteric effectors bind at specific sites, stabilizing either the T (inactive) or R (active) state, thereby modulating hemoglobin's oxygen affinity.

Question 14

Which of the following is a multi-step mechanism by which hemoglobin coordinates oxygen delivery and CO$$_2$$ removal?

Accepted Answer

CO$$_2 is $$converted to bicarbonate and a proton by carbonic anhydrase; the proton decreases pH, promoting oxygen release via the Bohr effect.

Question 15

Which of the following statements about hemocyanin is correct?

Accepted Answer

Hemocyanin uses copper atoms coordinated by histidine residues to bind oxygen, and is found in invertebrates.

Question 16

Which of the following best describes the induced fit model of protein-ligand interaction?

Accepted Answer

Ligand binding causes a conformational change in the protein, enhancing binding and function.

Question 17

Which of the following is true regarding the T to R transition in hemoglobin?

Accepted Answer

Oxygen binding causes the iron atom to move into the plane of the heme ring, triggering conformational changes that increase oxygen affinity.

Question 18

Which of the following is a correct statement about the role of carbaminohemoglobin in CO$$_2$$ transport?

Accepted Answer

Carbaminohemoglobin forms when CO$$_2$$ binds covalently to the N-terminus of hemoglobin chains, lowering oxygen affinity and promoting oxygen release.

Protein Function: Myoglobin and Hemoglobin – Structure, Function, and Regulation

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