Question 1

Which of the following best describes the primary force stabilizing the specific three-dimensional structure of a protein?

Accepted Answer

Non-covalent interactions such as hydrogen bonds, ionic interactions, and van der Waals forces

Question 2

A mutation replaces a glycine residue in the collagen triple helix with a serine. What is the most likely consequence?

Accepted Answer

The triple helix will be destabilized due to steric hindrance from the larger side chain.

Question 3

Which of the following statements about the peptide bond is correct?

Accepted Answer

It is rigid and planar due to resonance between the carbonyl and amide nitrogen.

Question 4

Which amino acid is most likely to be found in the interior of a globular protein?

Accepted Answer

Valine

Question 5

What is the main thermodynamic driving force for the folding of a globular protein in aqueous solution?

Accepted Answer

Hydrophobic effect, which increases entropy of water molecules

Question 6

Which of the following best describes a protein domain?

Accepted Answer

A part of a polypeptide chain that folds independently and has a specific function

Question 7

Which of the following is true regarding the Ramachandran plot?

Accepted Answer

It shows the possible values of $$\phi$$ and $$\psi$$ angles for peptide bonds without steric hindrance.

Question 8

Which of the following amino acids is most likely to disrupt an alpha helix?

Accepted Answer

Proline

Question 9

A protein is found to have multiple stable conformations. Which statement best explains this observation?

Accepted Answer

Proteins can undergo conformational changes, sometimes between a few stable states.

Question 10

Which of the following best describes the role of chaperone proteins in the cell?

Accepted Answer

They facilitate correct folding of newly synthesized or damaged proteins.

Question 11

Which of the following is a characteristic of fibrous proteins such as collagen?

Accepted Answer

They have a repetitive secondary structure and provide strength and flexibility.

Question 12

Which of the following statements about protein quaternary structure is correct?

Accepted Answer

It describes the spatial arrangement of multiple polypeptide subunits in a protein complex.

Question 13

Which of the following best explains why disulfide bonds are more common in extracellular proteins than in intracellular proteins?

Accepted Answer

The extracellular environment is more oxidizing, allowing disulfide bonds to form.

Question 14

Which of the following is a consequence of the hydrophobic effect in protein folding?

Accepted Answer

Hydrophobic side chains are buried in the protein core, increasing water entropy.

Question 15

A patient is diagnosed with sickle cell anemia. Which molecular event is responsible for this disease?

Accepted Answer

A substitution of valine for glutamate in the hemoglobin beta chain

Question 16

Which of the following best describes a protein motif?

Accepted Answer

A supersecondary structure formed by a specific combination of secondary elements

Question 17

Which of the following is true regarding intrinsically disordered protein segments?

Accepted Answer

They are rich in charged amino acids and lack a stable 3D structure.

Question 18

Which of the following statements about the Levinthal paradox is correct?

Accepted Answer

It suggests that proteins fold via specific pathways rather than random sampling.

Question 19

Which of the following best describes the role of the ubiquitin-proteasome system in proteostasis?

Accepted Answer

It tags misfolded or damaged proteins for degradation and recycles amino acids.

Protein Structure: Secondary, Tertiary, and Quaternary Organization

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