Q: Which of the following equations correctly represents the calculation of the length of an α-helix containing $$n$$ amino acids, given that each residue advances 1.5 Å along the helix axis?

$$\text{Length} = n \times 1.5\ \text{\AA}$$

Question 1

Which of the following best describes the primary structure of a protein?

Accepted Answer

The sequence of amino acids linked by peptide bonds

Question 2

Which type of bond is responsible for stabilizing the secondary structure of proteins such as α-helices and β-sheets?

Accepted Answer

Hydrogen bonds between the backbone N-H and C=O groups

Question 3

A mutation replaces a glycine residue with proline in the middle of an α-helix. What is the most likely effect on the protein structure?

Accepted Answer

The α-helix will be disrupted due to proline's rigid structure

Question 4

Which of the following equations correctly represents the calculation of the length of an α-helix containing $$n$$ amino acids, given that each residue advances 1.5 Å along the helix axis?

Accepted Answer

$$	ext{Length} = n 	imes 1.5\ 	ext{\AA}$$

Question 5

Which of the following interactions is NOT considered a non-covalent interaction in biological molecules?

Accepted Answer

Disulfide bond

Question 6

During protein folding, which thermodynamic factor is unfavorable and opposes folding?

Accepted Answer

Loss of conformational entropy

Question 7

Which amino acids are LEAST likely to be found in an α-helix, and why?

Accepted Answer

Proline and glycine, due to their unique backbone conformations

Question 8

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 entropy

Question 9

Which statement about disulfide bonds in proteins is CORRECT?

Accepted Answer

They form between two cysteine residues via oxidation of their thiol groups

Question 10

A protein is denatured by urea and β-mercaptoethanol. After removal of these agents, the protein regains its native structure and function. What does this experiment (Anfinsen's experiment) demonstrate?

Accepted Answer

The primary amino acid sequence determines the protein's 3D structure

Question 11

Which of the following best describes the tertiary structure of a protein?

Accepted Answer

The overall 3D arrangement of all atoms in a single polypeptide chain

Question 12

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

Accepted Answer

Bovine spongiform encephalopathy (mad cow disease)

Question 13

Which of the following statements about β-sheets is TRUE?

Accepted Answer

In anti-parallel β-sheets, the hydrogen bonds are nearly perpendicular to the strands

Question 14

Which equation correctly represents the calculation of the number of amino acids in a β-strand of length $$L$$ Å, given that each residue advances 3.4 Å?

Accepted Answer

$$n = \frac{L}{3.4}$$

Question 15

Which of the following is a favorable intramolecular enthalpic interaction that stabilizes protein structure?

Accepted Answer

Salt bridges (ionic bonds between charged side chains)

Question 16

Which of the following best describes the quaternary structure of a protein?

Accepted Answer

The arrangement and interaction of multiple polypeptide subunits

Question 17

Which of the following statements about Ramachandran plots is CORRECT?

Accepted Answer

They show the allowed values of the backbone dihedral angles $$\phi$$ and $$\psi$$ for amino acid residues in proteins

Question 18

Which of the following is a fibrous protein composed mainly of β-sheets?

Accepted Answer

Fibroin

Question 19

Scurvy is caused by a deficiency in vitamin C, which is required for the hydroxylation of which amino acids in collagen?

Accepted Answer

Proline and lysine

Question 20

Which of the following best explains why proteins can be denatured by heat or chemicals?

Accepted Answer

Heat or chemicals disrupt non-covalent interactions stabilizing the protein's structure

Protein Structure and Folding: Key Concepts in Biochemistry

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