Question 1

Which of the following best describes the role of molecular chaperones in proteostasis?

Accepted Answer

They assist in the correct folding of nascent and misfolded proteins, preventing aggregation.

Question 2

A protein is denatured by the addition of urea and β-mercaptoethanol. After removal of these chemicals, the protein regains its native structure and function. What does this experiment demonstrate?

Accepted Answer

The amino acid sequence alone contains all the information necessary for correct folding.

Question 3

Which of the following is a direct consequence of dysfunctional proteasomal degradation in cells?

Accepted Answer

Accumulation of misfolded proteins and potential formation of aggregates

Question 4

Which equation correctly represents the reversible binding of a protein (P) to its ligand (L) to form a protein-ligand complex (PL)?

Accepted Answer

$$ P + L \rightleftharpoons PL $$

Question 5

Hemoglobin displays a sigmoidal oxygen-binding curve because:

Accepted Answer

It undergoes cooperative binding, where binding of one O₂ increases affinity for additional O₂.

Question 6

Which of the following best explains why hemoglobin is more effective than myoglobin at delivering oxygen from the lungs to tissues?

Accepted Answer

Hemoglobin’s cooperative binding allows it to load oxygen efficiently in the lungs and release it in tissues.

Question 7

Which of the following is a homotropic modulator of hemoglobin?

Accepted Answer

Oxygen (O₂)

Question 8

A decrease in blood pH from 7.4 to 7.2 will have what effect on hemoglobin’s oxygen-binding curve?

Accepted Answer

Shift the curve to the right, decreasing oxygen affinity

Question 9

Which process is primarily responsible for degrading large protein aggregates and damaged organelles in the cell?

Accepted Answer

Autophagy-lysosome pathway

Question 10

Which of the following is NOT a possible fate of a misfolded protein in the cell?

Accepted Answer

Direct conversion into DNA

Question 11

A patient has a mutation that disrupts the function of Hsp70. Which cellular process is most likely to be impaired?

Accepted Answer

Protein folding and prevention of aggregation

Question 12

Which of the following best describes the role of the 19S regulatory cap in the proteasome?

Accepted Answer

It recognizes ubiquitin-tagged proteins and removes ubiquitin before degradation.

Question 13

Which of the following is a consequence of amyloid accumulation in cells?

Accepted Answer

Formation of insoluble protein aggregates associated with neurodegenerative diseases

Question 14

Which of the following statements about the heme group in myoglobin and hemoglobin is TRUE?

Accepted Answer

It is a non-protein prosthetic group containing an Fe²⁺ ion that binds oxygen.

Question 15

Which of the following best explains why oxygen binding to hemoglobin is described as allosteric?

Accepted Answer

Oxygen binding at one site increases the affinity at other sites through conformational changes.

Question 16

Which of the following is a real-life example of a disease caused by protein misfolding and aggregation?

Accepted Answer

Alzheimer’s disease

Question 17

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

Accepted Answer

Increased CO₂ and H⁺ lower hemoglobin’s oxygen affinity, promoting O₂ release in tissues.

Question 18

Which of the following is the correct order of protein structure formation?

Accepted Answer

Primary → Secondary → Tertiary → Quaternary

Question 19

Which of the following is a function of the nucleotide exchange factor (NEF) in the Hsp70 chaperone cycle?

Accepted Answer

It facilitates the release of ADP and binding of new ATP to Hsp70.

Protein Structure, Folding, Proteostasis, and Function

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