CHEM 210 Biochemistry Module 2 Exam: Amino Acids, Protein
Structure, and Function 2026/2027 UPDATE
1. Which amino acid lacks a chiral center at its alpha-carbon?
A. Glycine
B. Alanine
C. Valine
D. Proline
Answer: A
Rationale: Glycine is the only amino acid where the R-group is a hydrogen atom, making
the alpha-carbon symmetrical and thus achiral.
2. In a titration curve of an amino acid, what does the pI (isoelectric point)
represent?
A. The pH at which the amino acid has a net charge of zero
B. The pH at which the amino acid is entirely in its anionic form
C. The pH at which the amino acid has a net positive charge
D. The pH where buffering capacity is at its maximum
Answer: A
Rationale: The pI is the specific pH at which the zwitterion (neutral) form of the amino
acid is the predominant species, resulting in a net charge of zero.
,3. Which of the following amino acids contains a sulfur atom in its side chain but
cannot form disulfide bonds?
A. Cysteine
B. Methionine
C. Serine
D. Threonine
Answer: B
Rationale: Both Cysteine and Methionine contain sulfur, but only Cysteine has a reactive
thiol (-SH) group capable of forming disulfide bridges. Methionine has a thioether bond.
4. The peptide bond is characterized by which of the following properties?
A. Free rotation around the C-N bond
B. Partial double-bond character due to resonance
C. A length longer than a typical single bond
D. A non-planar geometry
Answer: B
Rationale: Due to resonance between the carbonyl oxygen and the amide nitrogen, the
peptide bond has partial double-bond character, making it rigid and planar.
5. Which level of protein structure is defined solely by the sequence of amino
acids linked by peptide bonds?
A. Tertiary structure
B. Secondary structure
C. Primary structure
D. Quaternary structure
Answer: C
Rationale: Primary structure refers to the linear arrangement of amino acid residues in a
polypeptide chain.
, 6. What type of interaction primarily stabilizes the alpha-helix and beta-sheet
structures?
A. Hydrophobic interactions
B. Hydrogen bonds between backbone atoms
C. Ionic bonds between R-groups
D. Disulfide bridges
Answer: B
Rationale: Secondary structures like alpha-helices and beta-sheets are stabilized by
hydrogen bonding between the carbonyl oxygen and the amide hydrogen of the
polypeptide backbone.
7. Which amino acid is known as a ‘helix breaker’ because its cyclic structure
limits rotation?
A. Leucine
B. Histidine
C. Proline
D. Phenylalanine
Answer: C
Rationale: Proline’s side chain is bonded back to the nitrogen of the amino group, creating
a rigid ring that interferes with the standard alpha-helix geometry.
8. The hydrophobic effect is the primary driving force for which level of protein
folding?
A. Primary
B. Tertiary
C. Secondary
D. Quaternary
Answer: B
Structure, and Function 2026/2027 UPDATE
1. Which amino acid lacks a chiral center at its alpha-carbon?
A. Glycine
B. Alanine
C. Valine
D. Proline
Answer: A
Rationale: Glycine is the only amino acid where the R-group is a hydrogen atom, making
the alpha-carbon symmetrical and thus achiral.
2. In a titration curve of an amino acid, what does the pI (isoelectric point)
represent?
A. The pH at which the amino acid has a net charge of zero
B. The pH at which the amino acid is entirely in its anionic form
C. The pH at which the amino acid has a net positive charge
D. The pH where buffering capacity is at its maximum
Answer: A
Rationale: The pI is the specific pH at which the zwitterion (neutral) form of the amino
acid is the predominant species, resulting in a net charge of zero.
,3. Which of the following amino acids contains a sulfur atom in its side chain but
cannot form disulfide bonds?
A. Cysteine
B. Methionine
C. Serine
D. Threonine
Answer: B
Rationale: Both Cysteine and Methionine contain sulfur, but only Cysteine has a reactive
thiol (-SH) group capable of forming disulfide bridges. Methionine has a thioether bond.
4. The peptide bond is characterized by which of the following properties?
A. Free rotation around the C-N bond
B. Partial double-bond character due to resonance
C. A length longer than a typical single bond
D. A non-planar geometry
Answer: B
Rationale: Due to resonance between the carbonyl oxygen and the amide nitrogen, the
peptide bond has partial double-bond character, making it rigid and planar.
5. Which level of protein structure is defined solely by the sequence of amino
acids linked by peptide bonds?
A. Tertiary structure
B. Secondary structure
C. Primary structure
D. Quaternary structure
Answer: C
Rationale: Primary structure refers to the linear arrangement of amino acid residues in a
polypeptide chain.
, 6. What type of interaction primarily stabilizes the alpha-helix and beta-sheet
structures?
A. Hydrophobic interactions
B. Hydrogen bonds between backbone atoms
C. Ionic bonds between R-groups
D. Disulfide bridges
Answer: B
Rationale: Secondary structures like alpha-helices and beta-sheets are stabilized by
hydrogen bonding between the carbonyl oxygen and the amide hydrogen of the
polypeptide backbone.
7. Which amino acid is known as a ‘helix breaker’ because its cyclic structure
limits rotation?
A. Leucine
B. Histidine
C. Proline
D. Phenylalanine
Answer: C
Rationale: Proline’s side chain is bonded back to the nitrogen of the amino group, creating
a rigid ring that interferes with the standard alpha-helix geometry.
8. The hydrophobic effect is the primary driving force for which level of protein
folding?
A. Primary
B. Tertiary
C. Secondary
D. Quaternary
Answer: B
