BioChem 210 Module 3 Exam: Amino Acids, Proteins, and Enzymes
2026 Questions and Answers 100% PASS
1. Which of the following amino acids is considered non-polar and hydrophobic?
A. Serine
B. Valine
C. Glutamate
D. Lysine
Answer: B
Rationale: Valine has a branched hydrocarbon side chain, making it non-polar and
hydrophobic. Serine is polar, Glutamate is acidic, and Lysine is basic.
2. What is the unique characteristic of the amino acid Glycine?
A. It is the only amino acid with a sulfur atom.
B. It has a cyclic side chain structure.
C. It is the only achiral amino acid.
D. It is the most hydrophobic amino acid.
Answer: C
Rationale: Glycine has a hydrogen atom as its R-group, meaning the alpha carbon is
bonded to two hydrogens, making it achiral.
3. Which bond stabilizes the primary structure of a protein?
A. Peptide bonds
B. Disulfide bridges
C. Hydrogen bonds
D. Ionic bonds
Answer: A
,Rationale: Primary structure refers to the linear sequence of amino acids linked by
covalent peptide bonds.
4. In a zwitterion, the net charge of the amino acid is:
A. Zero
B. Negative
C. Positive
D. Variable depending on the solvent
Answer: A
Rationale: A zwitterion contains both a positive charge (amino group) and a negative
charge (carboxylate group) that cancel each other out.
5. Which level of protein structure is characterized by alpha-helices and beta-
pleated sheets?
A. Primary
B. Tertiary
C. Secondary
D. Quaternary
Answer: C
Rationale: Secondary structure refers to local spatial arrangements of the polypeptide
backbone, stabilized by hydrogen bonds.
6. The side chain of which amino acid can form disulfide bridges?
A. Methionine
B. Proline
C. Arginine
D. Cysteine
Answer: D
Rationale: Cysteine contains a thiol (-SH) group that can oxidize to form a covalent
disulfide bond with another cysteine.
, 7. What happens to an enzyme’s activity during denaturation?
A. It increases significantly.
B. It remains unchanged.
C. It changes to catalyze a different reaction.
D. It is lost because the 3D shape is disrupted.
Answer: D
Rationale: Denaturation involves the unfolding of the protein, which destroys the active
site and eliminates catalytic activity.
8. Which of the following describes a competitive inhibitor?
A. It binds to the enzyme-substrate complex only.
B. It binds to the active site and competes with the substrate.
C. It binds to an allosteric site and changes enzyme shape.
D. It increases the Vmax of the reaction.
Answer: B
Rationale: Competitive inhibitors resemble the substrate and compete for the same active
site on the enzyme.
9. The Michaelis constant (Km) represents:
A. The maximum velocity of the reaction.
B. The substrate concentration at half of Vmax.
C. The total enzyme concentration.
D. The equilibrium constant of the reaction.
Answer: B
Rationale: Km is the substrate concentration at which the reaction rate is exactly half of
the maximum velocity (Vmax).
2026 Questions and Answers 100% PASS
1. Which of the following amino acids is considered non-polar and hydrophobic?
A. Serine
B. Valine
C. Glutamate
D. Lysine
Answer: B
Rationale: Valine has a branched hydrocarbon side chain, making it non-polar and
hydrophobic. Serine is polar, Glutamate is acidic, and Lysine is basic.
2. What is the unique characteristic of the amino acid Glycine?
A. It is the only amino acid with a sulfur atom.
B. It has a cyclic side chain structure.
C. It is the only achiral amino acid.
D. It is the most hydrophobic amino acid.
Answer: C
Rationale: Glycine has a hydrogen atom as its R-group, meaning the alpha carbon is
bonded to two hydrogens, making it achiral.
3. Which bond stabilizes the primary structure of a protein?
A. Peptide bonds
B. Disulfide bridges
C. Hydrogen bonds
D. Ionic bonds
Answer: A
,Rationale: Primary structure refers to the linear sequence of amino acids linked by
covalent peptide bonds.
4. In a zwitterion, the net charge of the amino acid is:
A. Zero
B. Negative
C. Positive
D. Variable depending on the solvent
Answer: A
Rationale: A zwitterion contains both a positive charge (amino group) and a negative
charge (carboxylate group) that cancel each other out.
5. Which level of protein structure is characterized by alpha-helices and beta-
pleated sheets?
A. Primary
B. Tertiary
C. Secondary
D. Quaternary
Answer: C
Rationale: Secondary structure refers to local spatial arrangements of the polypeptide
backbone, stabilized by hydrogen bonds.
6. The side chain of which amino acid can form disulfide bridges?
A. Methionine
B. Proline
C. Arginine
D. Cysteine
Answer: D
Rationale: Cysteine contains a thiol (-SH) group that can oxidize to form a covalent
disulfide bond with another cysteine.
, 7. What happens to an enzyme’s activity during denaturation?
A. It increases significantly.
B. It remains unchanged.
C. It changes to catalyze a different reaction.
D. It is lost because the 3D shape is disrupted.
Answer: D
Rationale: Denaturation involves the unfolding of the protein, which destroys the active
site and eliminates catalytic activity.
8. Which of the following describes a competitive inhibitor?
A. It binds to the enzyme-substrate complex only.
B. It binds to the active site and competes with the substrate.
C. It binds to an allosteric site and changes enzyme shape.
D. It increases the Vmax of the reaction.
Answer: B
Rationale: Competitive inhibitors resemble the substrate and compete for the same active
site on the enzyme.
9. The Michaelis constant (Km) represents:
A. The maximum velocity of the reaction.
B. The substrate concentration at half of Vmax.
C. The total enzyme concentration.
D. The equilibrium constant of the reaction.
Answer: B
Rationale: Km is the substrate concentration at which the reaction rate is exactly half of
the maximum velocity (Vmax).
