Question 1

Which of the following best describes a hydrogen bond in biological molecules?

Accepted Answer

An electrostatic attraction between a hydrogen atom covalently bonded to an electronegative atom and another electronegative atom.

Question 2

Which level of protein structure is primarily stabilized by peptide bonds?

Accepted Answer

Primary structure

Question 3

Given the following amino acids: leucine, serine, and lysine, which is classified as nonpolar?

Accepted Answer

Leucine

Question 4

If the pKa of the amino group in glycine is 9.6, what is the predominant ionization state of the amino group at pH 7.0?

Accepted Answer

Protonated ($$\mathrm{NH_3$^+})$$

Question 5

A peptide has the sequence Ala-Glu-Lys. At pH 7, what is the net charge of the peptide?

Accepted Answer

+1

Question 6

Which of the following best explains how hydrogen bonding contributes to the formation of the alpha helix in proteins?

Accepted Answer

Hydrogen bonds form between the carbonyl oxygen of one amino acid and the amide hydrogen of another, four residues ahead.

Question 7

Where are the side chains located in an alpha helix?

Accepted Answer

On the outside, projecting away from the helix axis

Question 8

Which type of non-covalent interaction is most likely to occur between the side chains of aspartate and lysine?

Accepted Answer

Ion-ion interaction

Question 9

The hydrophobic effect is critical for protein folding. Which statement best describes the role of entropy in this process?

Accepted Answer

The entropy of water increases as hydrophobic residues cluster together.

Question 10

Apply the formula $$\Delta G = \Delta H - T\Delta S to $$protein folding. Which scenario would result in a spontaneous folding process?

Accepted Answer

$$\Delta H is $$negative and $$\Delta S is $$positive

Question 11

Which of the following is a commonality among all non-covalent interactions?

Accepted Answer

They are reversible and depend on the proximity of interacting groups.

Question 12

Why are the energies of formation different for hydrogen bonds and van der Waals interactions?

Accepted Answer

Hydrogen bonds involve permanent dipoles, while van der Waals interactions involve temporary dipoles.

Question 13

A mutation replaces a nonpolar amino acid with a polar one in the interior of a protein. What is the most likely effect on protein structure?

Accepted Answer

The protein may become less stable due to disruption of hydrophobic packing.

Question 14

Which of the following best describes an ion-dipole interaction?

Accepted Answer

An interaction between an ion and a polar molecule.

Question 15

Which non-covalent interaction is most important in stabilizing the tertiary structure of a protein?

Accepted Answer

Hydrophobic interactions

Question 16

A protein is denatured by heat. Which type of interaction is most likely disrupted first?

Accepted Answer

Hydrogen bonds

Question 17

Which of the following amino acid pairs is most likely to form a hydrogen bond?

Accepted Answer

Serine and glutamine

Question 18

In a protein model, which visualization would best highlight the location of hydrophobic residues?

Accepted Answer

Space-filling model

Question 19

Which of the following statements about quaternary structure is correct?

Accepted Answer

It involves the association of multiple polypeptide chains.

Question 20

A protein has a high proportion of nonpolar amino acids on its surface. What is the most likely consequence?

Accepted Answer

The protein will tend to aggregate or associate with membranes.

Module 1

Study Guide - Practice Questions