Question 1

Which of the following best describes a heterotetrameric protein?

Accepted Answer

A protein composed of four different polypeptide chains

Question 2

Which type of interaction is primarily responsible for the burial of nonpolar side chains in the interior of a globular protein during folding?

Accepted Answer

Hydrophobic interactions

Question 3

The Ramachandran plot is used to visualize which of the following properties of a polypeptide chain?

Accepted Answer

The allowed values of the dihedral angles $\phi$ and $\psi$

Question 4

Which amino acid is most likely to be found at the center of the collagen triple helix, and why?

Accepted Answer

Glycine, because its small size fits the tight center

Question 5

Which of the following statements about protein denaturation is correct?

Accepted Answer

Denaturation disrupts non-covalent interactions, leading to loss of structure and function

Question 6

A protein is found to have two distinct domains, each with a different function. Which of the following is the most likely explanation for this structural feature?

Accepted Answer

The protein has undergone gene fusion, resulting in a multi-domain structure

Question 7

Which of the following best explains why proteins are only marginally stable under physiological conditions?

Accepted Answer

Marginal stability allows for necessary flexibility and motion required for function

Question 8

Which of the following is a correct statement about the secondary structure of proteins?

Accepted Answer

Secondary structure is stabilized by hydrogen bonds between backbone amide and carbonyl groups

Question 9

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

Accepted Answer

Proline

Question 10

A protein is found to be composed of two identical subunits. What is the best term to describe this protein's quaternary structure?

Accepted Answer

Homodimer

Question 11

Which of the following interactions is the strongest in stabilizing tertiary and quaternary protein structures?

Accepted Answer

Disulfide bonds

Question 12

Which of the following best describes the role of water molecules in the structure of globular proteins?

Accepted Answer

Water molecules form hydrogen bonds with polar side chains on the protein surface

Question 13

Which of the following is a correct statement about the folding information in the primary structure of a protein?

Accepted Answer

Folding information is encoded in the amino acid sequence

Question 14

Which of the following is a real-world example of protein denaturation?

Accepted Answer

The boiling of an egg white

Question 15

Which of the following best describes the structure of silk fibroin?

Accepted Answer

It is composed of extensive beta sheets with alternating Gly and Ala/Ser residues

Question 16

Which of the following statements about protein domains is correct?

Accepted Answer

Domains are independently folded regions that often have distinct functions

Question 17

Which of the following is a correct description of a coiled-coil protein structure?

Accepted Answer

A bundle of alpha helices wound into a left-handed superhelix

Question 18

Which of the following is NOT a typical force stabilizing the tertiary structure of proteins?

Accepted Answer

Peptide bonds

Question 19

Which of the following best explains why the free energy change ($\Delta G$) of protein folding is only slightly favorable?

Accepted Answer

The enthalpy gain from forming non-covalent interactions is only slightly greater than the entropy loss from folding

Question 20

Which of the following is an example of a conjugated protein?

Accepted Answer

Hemoglobin, which contains a heme prosthetic group

Introduction to Proteins: Structure, Types, and Biological Roles

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