WGU C785 Biochemistry Final Practice Exam 90 Questions | Accurate
& Verified Answers to Pass Actual Exam
1. What type of bond stabilizes the primary structure of a protein?
A. Hydrogen bonds
B. Ionic bonds
C. Disulfide bridges
D. Peptide bonds
Answer: D
Explanation: Primary structure refers to the sequence of amino acids held together by
covalent peptide bonds.
2. Which of the following describes the secondary structure of a protein?
A. The linear sequence of amino acids
B. The overall 3D folding of a single polypeptide
C. Alpha-helices and beta-pleated sheets
D. The interaction between multiple subunits
Answer: C
Explanation: Secondary structure is formed by hydrogen bonding between the backbone
atoms, resulting in alpha-helices and beta-sheets.
,3. What occurs when a protein is denatured?
A. The peptide bonds are broken
B. The primary structure is altered
C. The protein’s amino acid sequence changes
D. The protein loses its tertiary and secondary structures
Answer: D
Explanation: Denaturation involves the unfolding of the protein, losing its functional 3D
shape, while the primary sequence (peptide bonds) remains intact.
4. Which amino acid is known as a ‘helix breaker’ due to its rigid ring structure?
A. Glycine
B. Lysine
C. Alanine
D. Proline
Answer: D
Explanation: Proline has a cyclic R-group that creates a kink in the polypeptide chain,
making it unable to fit into a standard alpha-helix.
5. What is the effect of an enzyme on the activation energy of a reaction?
A. It decreases the activation energy
B. It has no effect on activation energy
C. It increases the activation energy
,D. It changes the Gibbs free energy (delta G)
Answer: A
Explanation: Enzymes act as catalysts by lowering the activation energy, allowing the
reaction to proceed faster.
6. In a Lineweaver-Burk plot, what does the x-intercept represent?
A. 1/Vmax
B. Vmax/Km
C. -1/Km
D. The slope
Answer: C
Explanation: On a double-reciprocal plot, the x-intercept is -1/Km and the y-intercept is
1/Vmax.
7. How does a competitive inhibitor affect an enzyme’s kinetics?
A. Decreases Km, Vmax decreases
B. Increases Km, Vmax stays the same
C. Km stays the same, Vmax decreases
D. Increases Km, Vmax decreases
Answer: B
, Explanation: Competitive inhibitors compete for the active site; increasing substrate
concentration can overcome the inhibition, so Vmax is unchanged but Km increases.
8. What is the role of 2,3-BPG in oxygen transport?
A. It increases hemoglobin’s affinity for oxygen
B. It stabilizes the T-state, promoting oxygen release
C. It stabilizes the R-state of hemoglobin
D. It binds to the iron atom in heme
Answer: B
Explanation: 2,3-BPG binds to the center of the hemoglobin tetramer in the T-state
(deoxygenated), reducing oxygen affinity to facilitate delivery to tissues.
9. Which shift in the hemoglobin oxygen dissociation curve represents the Bohr
effect?
A. A shift to the left due to high pH
B. A shift to the left due to low CO2
C. A shift to the right due to low pH and high CO2
D. A shift to the right due to fetal hemoglobin
Answer: C
Explanation: The Bohr effect describes how low pH (acidic) and high CO2 levels decrease
hemoglobin’s affinity for oxygen, shifting the curve to the right.
& Verified Answers to Pass Actual Exam
1. What type of bond stabilizes the primary structure of a protein?
A. Hydrogen bonds
B. Ionic bonds
C. Disulfide bridges
D. Peptide bonds
Answer: D
Explanation: Primary structure refers to the sequence of amino acids held together by
covalent peptide bonds.
2. Which of the following describes the secondary structure of a protein?
A. The linear sequence of amino acids
B. The overall 3D folding of a single polypeptide
C. Alpha-helices and beta-pleated sheets
D. The interaction between multiple subunits
Answer: C
Explanation: Secondary structure is formed by hydrogen bonding between the backbone
atoms, resulting in alpha-helices and beta-sheets.
,3. What occurs when a protein is denatured?
A. The peptide bonds are broken
B. The primary structure is altered
C. The protein’s amino acid sequence changes
D. The protein loses its tertiary and secondary structures
Answer: D
Explanation: Denaturation involves the unfolding of the protein, losing its functional 3D
shape, while the primary sequence (peptide bonds) remains intact.
4. Which amino acid is known as a ‘helix breaker’ due to its rigid ring structure?
A. Glycine
B. Lysine
C. Alanine
D. Proline
Answer: D
Explanation: Proline has a cyclic R-group that creates a kink in the polypeptide chain,
making it unable to fit into a standard alpha-helix.
5. What is the effect of an enzyme on the activation energy of a reaction?
A. It decreases the activation energy
B. It has no effect on activation energy
C. It increases the activation energy
,D. It changes the Gibbs free energy (delta G)
Answer: A
Explanation: Enzymes act as catalysts by lowering the activation energy, allowing the
reaction to proceed faster.
6. In a Lineweaver-Burk plot, what does the x-intercept represent?
A. 1/Vmax
B. Vmax/Km
C. -1/Km
D. The slope
Answer: C
Explanation: On a double-reciprocal plot, the x-intercept is -1/Km and the y-intercept is
1/Vmax.
7. How does a competitive inhibitor affect an enzyme’s kinetics?
A. Decreases Km, Vmax decreases
B. Increases Km, Vmax stays the same
C. Km stays the same, Vmax decreases
D. Increases Km, Vmax decreases
Answer: B
, Explanation: Competitive inhibitors compete for the active site; increasing substrate
concentration can overcome the inhibition, so Vmax is unchanged but Km increases.
8. What is the role of 2,3-BPG in oxygen transport?
A. It increases hemoglobin’s affinity for oxygen
B. It stabilizes the T-state, promoting oxygen release
C. It stabilizes the R-state of hemoglobin
D. It binds to the iron atom in heme
Answer: B
Explanation: 2,3-BPG binds to the center of the hemoglobin tetramer in the T-state
(deoxygenated), reducing oxygen affinity to facilitate delivery to tissues.
9. Which shift in the hemoglobin oxygen dissociation curve represents the Bohr
effect?
A. A shift to the left due to high pH
B. A shift to the left due to low CO2
C. A shift to the right due to low pH and high CO2
D. A shift to the right due to fetal hemoglobin
Answer: C
Explanation: The Bohr effect describes how low pH (acidic) and high CO2 levels decrease
hemoglobin’s affinity for oxygen, shifting the curve to the right.
