Question 1

Which of the following best describes the process by which preproinsulin is converted to mature insulin in the human body?

Accepted Answer

Preproinsulin undergoes folding, disulfide bond formation, and sequential proteolytic cleavages to yield mature insulin.

Question 2

Which of the following statements about the oxygen-binding curves of myoglobin and hemoglobin is correct?

Accepted Answer

Myoglobin displays a hyperbolic oxygen-binding curve, while hemoglobin displays a sigmoidal curve due to cooperative binding.

Question 3

Which of the following is a physiological advantage of producing digestive enzymes as inactive precursors (zymogens) in the pancreas?

Accepted Answer

It prevents the enzymes from digesting pancreatic tissue before reaching the gut.

Question 4

Which of the following best explains the Bohr effect in hemoglobin function?

Accepted Answer

A decrease in pH (increase in [H+]) decreases hemoglobin's affinity for O2, promoting O2 release in tissues.

Question 5

Which of the following is a key structural feature that allows antibodies to recognize a vast array of antigens?

Accepted Answer

The hypervariable complementarity-determining regions (CDRs) in the variable domains.

Question 6

A patient with a mutation that prevents the formation of disulfide bonds in proinsulin would most likely experience which of the following?

Accepted Answer

Impaired insulin folding and inability to produce active insulin.

Question 7

Which of the following best describes the role of 2,3-bisphosphoglycerate (2,3-BPG) in oxygen transport by hemoglobin?

Accepted Answer

2,3-BPG decreases hemoglobin's affinity for oxygen, favoring the T-state and promoting oxygen release in tissues.

Question 8

Which of the following statements about the structure of immunoglobulin G (IgG) is correct?

Accepted Answer

IgG consists of two identical heavy chains and two identical light chains held together by disulfide bonds.

Question 9

A mutation in the gene encoding the proximal histidine of myoglobin would most likely affect which aspect of its function?

Accepted Answer

The ability of myoglobin to bind oxygen at the heme group.

Question 10

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

Accepted Answer

HbF binds 2,3-BPG less strongly than HbA, favoring the R-state and higher oxygen affinity.

Question 11

Which of the following scenarios would most likely result in a rightward shift of the hemoglobin-oxygen dissociation curve?

Accepted Answer

Increased CO2, increased temperature, and increased 2,3-BPG concentration.

Question 12

Which of the following is a direct consequence of the cooperative binding of oxygen to hemoglobin?

Accepted Answer

The binding of one oxygen molecule increases the affinity of the remaining subunits for oxygen.

Question 13

Which of the following best describes the molecular mechanism underlying the T to R transition in hemoglobin upon oxygen binding?

Accepted Answer

Oxygen binding flattens the heme group, pulling the Fe2+ into the plane and triggering a conformational change that disrupts salt bridges and stabilizes the R-state.

Question 14

Which of the following is a function of the Fc region of an antibody molecule?

Accepted Answer

Signaling other immune cells, such as macrophages, to attack marked cells.

Question 15

Which of the following best explains why B-cells that produce antibodies against self-antigens are not normally found in circulation?

Accepted Answer

They are destroyed during development if they bind self-antigens, preventing autoimmunity.

Question 16

Which of the following is a key difference between the humoral and cellular branches of the adaptive immune response?

Accepted Answer

The humoral response involves B-lymphocytes producing antibodies, while the cellular response involves T-lymphocytes destroying infected cells.

Question 17

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

Accepted Answer

It forms a hydrogen bond with bound oxygen, increasing selectivity for O2 over CO.

Question 18

A patient is exposed to high altitude for several days. Which of the following adaptations would you expect to occur in their red blood cells to facilitate oxygen delivery to tissues?

Accepted Answer

Increase in 2,3-BPG concentration, decreasing hemoglobin's oxygen affinity and promoting oxygen release.

Protein Function and Evolution: Immunoglobulins, Oxygen Transport, and Allosteric Regulation

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