C785 Biochemistry Module 1 Comprehensive Practice Quiz 2026
|WGU
1. Which of the following is the primary force that stabilizes the alpha-helix and
beta-sheet structures in proteins?
A. Disulfide bridges
B. Hydrogen bonds between backbone atoms
C. Hydrophobic interactions between side chains
D. Ionic bonds between acidic and basic residues
Answer: B
Rationale: Secondary structures like alpha-helices and beta-sheets are stabilized by
hydrogen bonds between the carbonyl oxygen and the amide hydrogen of the polypeptide
backbone.
2. Which amino acid substitution is responsible for the formation of hemoglobin
S in sickle cell anemia?
A. Glutamic acid to Valine
B. Valine to Glutamic acid
C. Lysine to Arginine
D. Alanine to Glycine
Answer: A
Rationale: Sickle cell anemia is caused by a point mutation where a hydrophilic glutamic
acid is replaced by a hydrophobic valine at the sixth position of the beta-globin chain.
,3. In an aqueous environment, where would you most likely find non-polar
amino acids in a globular protein?
A. On the surface of the protein
B. Buried in the interior of the protein
C. Interacting with the water molecules
D. Forming peptide bonds with basic amino acids
Answer: B
Rationale: Due to the hydrophobic effect, non-polar side chains aggregate in the interior of
the protein to avoid contact with water, helping the protein fold.
4. Which level of protein structure is defined by the specific sequence of amino
acids linked by peptide bonds?
A. Primary structure
B. Tertiary structure
C. Quaternary structure
D. Secondary structure
Answer: A
Rationale: Primary structure refers specifically to the linear sequence of amino acids in a
polypeptide chain.
5. How does an enzyme increase the rate of a chemical reaction?
A. By increasing the temperature of the reactants
B. By lowering the activation energy
C. By increasing the Gibbs free energy
D. By changing the equilibrium constant
Answer: B
Rationale: Enzymes act as biological catalysts that speed up reactions by lowering the
activation energy required for the transition state to form.
, 6. Which molecule binds to the iron atom in the heme group of hemoglobin and
competes with oxygen?
A. Carbon monoxide
B. 2,3-Bisphosphoglycerate
C. Carbon dioxide
D. Bicarbonate
Answer: A
Rationale: Carbon monoxide (CO) has a much higher affinity for the heme iron than
oxygen, preventing oxygen from binding and causing toxicity.
7. The ‘induced fit’ model of enzyme-substrate interaction suggests that:
A. The enzyme and substrate undergo conformational changes upon binding.
B. The active site is a rigid lock into which the substrate fits exactly.
C. Enzymes only bind to substrates that have the same charge.
D. The substrate changes its chemical identity before binding to the enzyme.
Answer: A
Rationale: Induced fit means the enzyme’s active site shifts its shape slightly to more
tightly bind the substrate once it enters.
8. What happens to hemoglobin’s affinity for oxygen when the pH of the blood
decreases (Bohr Effect)?
A. Affinity increases
B. Affinity remains unchanged
C. Affinity decreases
D. Hemoglobin denatures immediately
Answer: C
Rationale: A decrease in pH (increased acidity) stabilizes the T-state (tense state) of
hemoglobin, decreasing its affinity for oxygen and promoting oxygen release to tissues.
|WGU
1. Which of the following is the primary force that stabilizes the alpha-helix and
beta-sheet structures in proteins?
A. Disulfide bridges
B. Hydrogen bonds between backbone atoms
C. Hydrophobic interactions between side chains
D. Ionic bonds between acidic and basic residues
Answer: B
Rationale: Secondary structures like alpha-helices and beta-sheets are stabilized by
hydrogen bonds between the carbonyl oxygen and the amide hydrogen of the polypeptide
backbone.
2. Which amino acid substitution is responsible for the formation of hemoglobin
S in sickle cell anemia?
A. Glutamic acid to Valine
B. Valine to Glutamic acid
C. Lysine to Arginine
D. Alanine to Glycine
Answer: A
Rationale: Sickle cell anemia is caused by a point mutation where a hydrophilic glutamic
acid is replaced by a hydrophobic valine at the sixth position of the beta-globin chain.
,3. In an aqueous environment, where would you most likely find non-polar
amino acids in a globular protein?
A. On the surface of the protein
B. Buried in the interior of the protein
C. Interacting with the water molecules
D. Forming peptide bonds with basic amino acids
Answer: B
Rationale: Due to the hydrophobic effect, non-polar side chains aggregate in the interior of
the protein to avoid contact with water, helping the protein fold.
4. Which level of protein structure is defined by the specific sequence of amino
acids linked by peptide bonds?
A. Primary structure
B. Tertiary structure
C. Quaternary structure
D. Secondary structure
Answer: A
Rationale: Primary structure refers specifically to the linear sequence of amino acids in a
polypeptide chain.
5. How does an enzyme increase the rate of a chemical reaction?
A. By increasing the temperature of the reactants
B. By lowering the activation energy
C. By increasing the Gibbs free energy
D. By changing the equilibrium constant
Answer: B
Rationale: Enzymes act as biological catalysts that speed up reactions by lowering the
activation energy required for the transition state to form.
, 6. Which molecule binds to the iron atom in the heme group of hemoglobin and
competes with oxygen?
A. Carbon monoxide
B. 2,3-Bisphosphoglycerate
C. Carbon dioxide
D. Bicarbonate
Answer: A
Rationale: Carbon monoxide (CO) has a much higher affinity for the heme iron than
oxygen, preventing oxygen from binding and causing toxicity.
7. The ‘induced fit’ model of enzyme-substrate interaction suggests that:
A. The enzyme and substrate undergo conformational changes upon binding.
B. The active site is a rigid lock into which the substrate fits exactly.
C. Enzymes only bind to substrates that have the same charge.
D. The substrate changes its chemical identity before binding to the enzyme.
Answer: A
Rationale: Induced fit means the enzyme’s active site shifts its shape slightly to more
tightly bind the substrate once it enters.
8. What happens to hemoglobin’s affinity for oxygen when the pH of the blood
decreases (Bohr Effect)?
A. Affinity increases
B. Affinity remains unchanged
C. Affinity decreases
D. Hemoglobin denatures immediately
Answer: C
Rationale: A decrease in pH (increased acidity) stabilizes the T-state (tense state) of
hemoglobin, decreasing its affinity for oxygen and promoting oxygen release to tissues.
