Question 1

Which level of protein structure is primarily stabilized by hydrogen bonds between the carbonyl and amino groups of the backbone, rather than interactions between side chains?

Accepted Answer

Secondary structure

Question 2

A mutation changes a single amino acid in hemoglobin from glutamic acid (Glu, E) to valine (Val, V). This change leads to sickle cell anemia. Which property of the amino acid side chain is most responsible for this disease phenotype?

Accepted Answer

Change from a charged to a nonpolar side chain

Question 3

Which of the following amino acid substitutions is most likely to be 'silent' (least likely to affect protein properties)?

Accepted Answer

Arginine (Arg, R) to Lysine (Lys, K)

Question 4

Which of the following best explains why nonpolar amino acid side chains are typically found in the interior of a folded protein?

Accepted Answer

Nonpolar side chains are repelled by water due to the hydrophobic effect

Question 5

Which of the following bonds is responsible for stabilizing the primary structure of a protein?

Accepted Answer

Peptide bonds between amino acids

Question 6

During protein folding, which thermodynamic parameter is most directly increased as nonpolar side chains aggregate in the protein core?

Accepted Answer

Entropy of water ($\Delta S_{water}$)

Question 7

Which of the following correctly describes the directionality of a polypeptide chain during synthesis?

Accepted Answer

N-terminus to C-terminus

Question 8

A protein is exposed to high concentrations of urea, causing it to unfold. Which level(s) of protein structure are most directly disrupted by this treatment?

Accepted Answer

Secondary, tertiary, and quaternary structures

Question 9

Which of the following interactions is NOT typically involved in stabilizing tertiary protein structure?

Accepted Answer

Peptide bonds between amino acids

Question 10

Which equation correctly relates Gibbs free energy to enthalpy, entropy, and temperature?

Accepted Answer

$\Delta G = \Delta H - T\Delta S$

Question 11

Which of the following statements about peptide bonds is TRUE?

Accepted Answer

Peptide bonds are planar and rigid due to partial double-bond character

Question 12

A protein consists of two identical polypeptide chains that interact to form a functional unit. What is the term for this type of quaternary structure?

Accepted Answer

Homodimer

Question 13

Which of the following amino acids is the smallest and most flexible, often found in turns or loops of proteins?

Accepted Answer

Glycine

Question 14

Which of the following is a real-world example of a protein whose function is altered by a single amino acid substitution?

Accepted Answer

Hemoglobin in sickle cell anemia

Question 15

Which of the following best describes the hydrophobic effect in protein folding?

Accepted Answer

Nonpolar side chains aggregate to minimize water ordering, increasing entropy

Question 16

Which of the following is TRUE regarding the quaternary structure of proteins?

Accepted Answer

Quaternary structure involves interactions between multiple polypeptide chains

Question 17

Which of the following is a consequence of the planar nature of the peptide bond?

Accepted Answer

Rotation is restricted at the peptide bond, but allowed at adjacent bonds

Question 18

Which of the following is most likely to disrupt disulfide bonds in a protein?

Accepted Answer

Reducing agents such as dithiothreitol (DTT)

Question 19

Which of the following statements about enzyme-catalyzed reactions is TRUE?

Accepted Answer

Enzymes lower the activation energy but do not affect $\Delta G$

Question 20

Which of the following is a correct statement about coupled reactions in metabolism?

Accepted Answer

Endergonic reactions ($\Delta G > 0$) can proceed if coupled to exergonic reactions ($\Delta G < 0$)

Protein Structure and Function: Study Notes

Study Guide - Practice Questions

Study Guide - Flashcards