Q: Collagen is characterized by a triple-stranded helix stabilized by which repeating tripeptide motif?

$\text{Gly-X-Y}$, where X is Pro and Y is Pro or hydroxyproline

Question 1

Which of the following statements best describes the role of hydrogen bonds in protein secondary structure formation according to Pauling’s rules?

Accepted Answer

Hydrogen bonds stabilize the folding processes and products by forming between backbone amide groups.

Question 2

A Ramachandran plot is used to visualize which aspect of protein structure?

Accepted Answer

Sterically allowed values of the backbone dihedral angles $\phi$ and $\psi$ for polypeptides.

Question 3

Which amino acid is most likely to disrupt an $\alpha$-helix due to its unique side chain structure?

Accepted Answer

Proline

Question 4

Collagen is characterized by a triple-stranded helix stabilized by which repeating tripeptide motif?

Accepted Answer

$	ext{Gly-X-Y}$, where X is Pro and Y is Pro or hydroxyproline

Question 5

Which of the following best explains the 'hydrophobic effect' in protein folding?

Accepted Answer

Hydrophobic side chains cluster in the protein interior, releasing ordered water molecules and increasing solvent entropy.

Question 6

Which experimental technique is most suitable for determining the molecular mass of native protein structures?

Accepted Answer

Size exclusion chromatography

Question 7

A protein is found to have a nonpolar interior and a hydrophilic exterior. This is a typical feature of which class of proteins?

Accepted Answer

Globular proteins

Question 8

Which of the following statements about protein folding is supported by Anfinsen’s experiment with ribonuclease A?

Accepted Answer

The information required for folding into the native structure is contained in the amino acid sequence.

Question 9

Which type of secondary structure is stabilized by hydrogen bonds that are nearly parallel to the helix axis and has side chains radiating outward?

Accepted Answer

$\alpha$-helix

Question 10

Disulfide bonds in proteins primarily contribute to stability by:

Accepted Answer

Reducing the number of possible unfolded conformations, thus decreasing entropy.

Question 11

Which of the following is a consequence of the partial double bond character of the peptide bond in proteins?

Accepted Answer

The atoms in the amide plane are basically fixed, restricting rotation.

Question 12

Which protein folding intermediate is described as a compact, partially folded state with native-like secondary structure but not fully formed tertiary interactions?

Accepted Answer

Molten globule state

Question 13

Which of the following is TRUE regarding the symmetry of quaternary protein structures?

Accepted Answer

C$_n$ symmetry involves one n-fold axis of symmetry.

Question 14

Which of the following is a major difference between fibrous and globular proteins?

Accepted Answer

Fibrous proteins are elongated and serve structural roles, while globular proteins fold into compact shapes with diverse functions.

Question 15

Which of the following is a common misconception about the folding pathway of proteins?

Accepted Answer

Proteins fold by sampling all possible conformations randomly until the most stable is found.

Question 16

Which of the following diseases is associated with the formation of amyloid fibrils due to protein misfolding?

Accepted Answer

Alzheimer’s disease

Question 17

Which of the following best describes the function of chaperones in the cell?

Accepted Answer

Chaperones prevent aggregation by assisting proper protein folding, especially under stress.

Question 18

Which of the following methods is most accurate for determining the number and approximate molecular masses of protein subunits under denaturing conditions?

Accepted Answer

SDS-PAGE with a reducing agent

Question 19

Which of the following is a key thermodynamic factor favoring protein folding?

Accepted Answer

Gain of solvent entropy from burying hydrophobic groups

Question 20

Which secondary structure element is stabilized by interchain hydrogen bonds and has side chains alternating above and below the plane?

Accepted Answer

$\beta$-sheet

The Three-Dimensional Structure of Proteins

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