CHEM 219 MODULE 3: AMINO ACIDS,
PROTEINS, AND ENZYMES QUESTIONS
WITH CORRECT ANSWERS 2026/2027
UPDATE. JUST RELEASED
1. Which of the following amino acids lacks a chiral center at the alpha-carbon?
A. Alanine
B. Proline
C. Glycine
D. Valine
Answer: C
Conceptual Explanation: Glycine is the only proteogenic amino acid where the R-group is
a hydrogen atom, making the alpha-carbon achiral because it is bonded to two identical
hydrogen atoms.
2. In the folding of a globular protein, which force is considered the primary driving factor?
A. The hydrophobic effect
B. Disulfide bridge formation
C. Hydrogen bonding
D. Ionic interactions
,Answer: A
Conceptual Explanation: The hydrophobic effect, which drives non-polar side chains to
the interior of the protein to minimize contact with water, is the major driving force for
protein folding.
3. At a pH equal to the isoelectric point (pI) of an amino acid, what is the net charge?
A. Zero
B. Negative
C. Positive
D. Highly variable
Answer: A
Conceptual Explanation: The isoelectric point is the specific pH at which an amino acid
exists primarily as a zwitterion, resulting in a net electrical charge of zero.
4. The peptide bond is characterized by which of the following properties?
A. Free rotation about the C-N bond
B. Triple bond formation
C. Complete ionic character
D. A partial double-bond character
Answer: D
, Conceptual Explanation: Due to resonance, the peptide bond has about 40% double-bond
character, which restricts rotation and keeps the atoms of the peptide group in a planar
configuration.
5. In a standard alpha-helix, the hydrogen bonds occur between which groups?
A. The C=O of residue i and the N-H of residue i+3
B. The C=O of residue i and the N-H of residue i+4
C. Side chain R-groups
D. The N-terminus and C-terminus
Answer: B
Conceptual Explanation: The alpha-helix is stabilized by intrachain hydrogen bonds
between the carbonyl oxygen of one amino acid (i) and the amide hydrogen four residues
ahead (i+4).
6. Which amino acid is most likely to be found in a beta-turn due to its unique cyclic
structure?
A. Leucine
B. Proline
C. Tryptophan
D. Methionine
Answer: B
PROTEINS, AND ENZYMES QUESTIONS
WITH CORRECT ANSWERS 2026/2027
UPDATE. JUST RELEASED
1. Which of the following amino acids lacks a chiral center at the alpha-carbon?
A. Alanine
B. Proline
C. Glycine
D. Valine
Answer: C
Conceptual Explanation: Glycine is the only proteogenic amino acid where the R-group is
a hydrogen atom, making the alpha-carbon achiral because it is bonded to two identical
hydrogen atoms.
2. In the folding of a globular protein, which force is considered the primary driving factor?
A. The hydrophobic effect
B. Disulfide bridge formation
C. Hydrogen bonding
D. Ionic interactions
,Answer: A
Conceptual Explanation: The hydrophobic effect, which drives non-polar side chains to
the interior of the protein to minimize contact with water, is the major driving force for
protein folding.
3. At a pH equal to the isoelectric point (pI) of an amino acid, what is the net charge?
A. Zero
B. Negative
C. Positive
D. Highly variable
Answer: A
Conceptual Explanation: The isoelectric point is the specific pH at which an amino acid
exists primarily as a zwitterion, resulting in a net electrical charge of zero.
4. The peptide bond is characterized by which of the following properties?
A. Free rotation about the C-N bond
B. Triple bond formation
C. Complete ionic character
D. A partial double-bond character
Answer: D
, Conceptual Explanation: Due to resonance, the peptide bond has about 40% double-bond
character, which restricts rotation and keeps the atoms of the peptide group in a planar
configuration.
5. In a standard alpha-helix, the hydrogen bonds occur between which groups?
A. The C=O of residue i and the N-H of residue i+3
B. The C=O of residue i and the N-H of residue i+4
C. Side chain R-groups
D. The N-terminus and C-terminus
Answer: B
Conceptual Explanation: The alpha-helix is stabilized by intrachain hydrogen bonds
between the carbonyl oxygen of one amino acid (i) and the amide hydrogen four residues
ahead (i+4).
6. Which amino acid is most likely to be found in a beta-turn due to its unique cyclic
structure?
A. Leucine
B. Proline
C. Tryptophan
D. Methionine
Answer: B
