CHEM 210 Biochemistry Module 4: Protein Structure, Function, and
Enzymes Geneva College
1. Which of the following stabilizes the secondary structure of proteins?
A. Disulfide bridges
B. Salt bridges between polar residues
C. Hydrophobic interactions between side chains
D. Hydrogen bonds between backbone atoms
Answer: D
Rationale: Secondary structure elements like alpha-helices and beta-sheets are primarily
stabilized by hydrogen bonds between the carbonyl oxygen and the amide hydrogen of the
polypeptide backbone.
2. Which amino acid is known as a ‘helix breaker’ because it lacks a hydrogen on
its nitrogen atom when in a peptide bond?
A. Glycine
B. Proline
C. Alanine
D. Valine
Answer: B
Rationale: Proline has a cyclic structure that introduces a kink in the peptide chain and
lacks the amide hydrogen necessary for standard alpha-helical hydrogen bonding.
,3. In an alpha-helix, the CO group of residue ‘i’ forms a hydrogen bond with the
NH group of which residue?
A. i + 3
B. i + 5
C. i + 4
D. i + 2
Answer: C
Rationale: The standard alpha-helix is characterized by hydrogen bonds between the C=O
of residue n and the N-H of residue n+4.
4. What is the primary characteristic of the tertiary structure of a protein?
A. The linear sequence of amino acids
B. Local folding into repetitive patterns
C. The overall three-dimensional arrangement of all atoms in a single polypeptide
D. The assembly of multiple polypeptide subunits
Answer: C
Rationale: Tertiary structure refers to the complete three-dimensional folding of a single
polypeptide chain, including the spatial relationship of far-apart residues.
5. Which molecule binds to the central cavity of the hemoglobin tetramer and
decreases its oxygen affinity?
A. Carbon monoxide
B. Nitric oxide
C. 2,3-Bisphosphoglycerate (2,3-BPG)
D. Glucose
Answer: C
Rationale: 2,3-BPG is a highly anionic molecule that binds to the T-state of hemoglobin,
stabilizing it and promoting the release of oxygen.
, 6. What type of curve represents the oxygen binding affinity of Myoglobin?
A. Sigmoidal
B. Hyperbolic
C. Linear
D. Parabolic
Answer: B
Rationale: Myoglobin shows a hyperbolic binding curve because it binds oxygen
independently and does not exhibit cooperativity.
7. The Bohr Effect describes the influence of which factors on hemoglobin’s
affinity for oxygen?
A. Temperature and pressure
B. Iron concentration and light
C. pH and CO2 concentration
D. Glucose levels and salt concentration
Answer: C
Rationale: The Bohr Effect refers to the observation that lower pH (higher H+
concentration) and higher CO2 levels decrease hemoglobin’s affinity for oxygen.
8. Which protein structure level is defined by the sequence of amino acids
linked by peptide bonds?
A. Primary
B. Secondary
C. Tertiary
D. Quaternary
Answer: A
Rationale: The primary structure is the linear sequence of amino acid residues in a
protein.
Enzymes Geneva College
1. Which of the following stabilizes the secondary structure of proteins?
A. Disulfide bridges
B. Salt bridges between polar residues
C. Hydrophobic interactions between side chains
D. Hydrogen bonds between backbone atoms
Answer: D
Rationale: Secondary structure elements like alpha-helices and beta-sheets are primarily
stabilized by hydrogen bonds between the carbonyl oxygen and the amide hydrogen of the
polypeptide backbone.
2. Which amino acid is known as a ‘helix breaker’ because it lacks a hydrogen on
its nitrogen atom when in a peptide bond?
A. Glycine
B. Proline
C. Alanine
D. Valine
Answer: B
Rationale: Proline has a cyclic structure that introduces a kink in the peptide chain and
lacks the amide hydrogen necessary for standard alpha-helical hydrogen bonding.
,3. In an alpha-helix, the CO group of residue ‘i’ forms a hydrogen bond with the
NH group of which residue?
A. i + 3
B. i + 5
C. i + 4
D. i + 2
Answer: C
Rationale: The standard alpha-helix is characterized by hydrogen bonds between the C=O
of residue n and the N-H of residue n+4.
4. What is the primary characteristic of the tertiary structure of a protein?
A. The linear sequence of amino acids
B. Local folding into repetitive patterns
C. The overall three-dimensional arrangement of all atoms in a single polypeptide
D. The assembly of multiple polypeptide subunits
Answer: C
Rationale: Tertiary structure refers to the complete three-dimensional folding of a single
polypeptide chain, including the spatial relationship of far-apart residues.
5. Which molecule binds to the central cavity of the hemoglobin tetramer and
decreases its oxygen affinity?
A. Carbon monoxide
B. Nitric oxide
C. 2,3-Bisphosphoglycerate (2,3-BPG)
D. Glucose
Answer: C
Rationale: 2,3-BPG is a highly anionic molecule that binds to the T-state of hemoglobin,
stabilizing it and promoting the release of oxygen.
, 6. What type of curve represents the oxygen binding affinity of Myoglobin?
A. Sigmoidal
B. Hyperbolic
C. Linear
D. Parabolic
Answer: B
Rationale: Myoglobin shows a hyperbolic binding curve because it binds oxygen
independently and does not exhibit cooperativity.
7. The Bohr Effect describes the influence of which factors on hemoglobin’s
affinity for oxygen?
A. Temperature and pressure
B. Iron concentration and light
C. pH and CO2 concentration
D. Glucose levels and salt concentration
Answer: C
Rationale: The Bohr Effect refers to the observation that lower pH (higher H+
concentration) and higher CO2 levels decrease hemoglobin’s affinity for oxygen.
8. Which protein structure level is defined by the sequence of amino acids
linked by peptide bonds?
A. Primary
B. Secondary
C. Tertiary
D. Quaternary
Answer: A
Rationale: The primary structure is the linear sequence of amino acid residues in a
protein.
