C785 Biochemistry Final Exam Version 3 Practice Questions 2026
|WGU
1. Which level of protein structure is characterized by the formation of alpha-
helices and beta-pleated sheets?
A. Primary structure
B. Tertiary structure
C. Secondary structure
D. Quaternary structure
Answer: C
Rationale: Secondary structure refers to local folded structures that form within a
polypeptide due to interactions between atoms of the backbone, specifically hydrogen
bonding.
2. What is the primary function of an enzyme in a biochemical reaction?
A. To decrease the activation energy
B. To increase the Gibbs free energy of the reaction
C. To change the equilibrium constant
D. To be consumed in the reaction
Answer: A
Rationale: Enzymes act as catalysts by lowering the activation energy required for a
reaction to proceed, thereby increasing the rate of the reaction.
,3. In the Michaelis-Menten equation, what does Km represent?
A. The substrate concentration at which velocity is half of Vmax
B. The maximum velocity of the reaction
C. The turnover number
D. The total enzyme concentration
Answer: A
Rationale: Km is the Michaelis constant, which indicates the substrate concentration at
which the reaction rate is 50% of the maximum velocity (Vmax).
4. Which molecule acts as the final electron acceptor in the electron transport
chain during aerobic respiration?
A. NAD+
B. FAD
C. Water
D. Oxygen
Answer: D
Rationale: Oxygen (O2) is the final electron acceptor in the electron transport chain, where
it is reduced to form water.
5. Which enzyme is responsible for unwinding the DNA double helix during
replication?
A. Helicase
B. DNA Ligase
C. DNA Polymerase
D. Primase
Answer: A
Rationale: Helicase is the enzyme that breaks the hydrogen bonds between the base pairs
to unzip the DNA strands.
, 6. What is the result of a nonsense mutation in a DNA sequence?
A. A different amino acid is incorporated into the protein
B. A premature stop codon is introduced
C. The protein sequence remains unchanged
D. The reading frame is shifted
Answer: B
Rationale: A nonsense mutation changes an amino acid codon into a stop codon, leading to
a truncated and usually nonfunctional protein.
7. Which of the following is a characteristic of competitive inhibition?
A. Km is increased
B. Vmax is decreased
C. The inhibitor binds to an allosteric site
D. The inhibitor binds only to the enzyme-substrate complex
Answer: A
Rationale: In competitive inhibition, the inhibitor competes with the substrate for the
active site, effectively increasing the Km while Vmax remains unchanged.
8. What is the primary role of Myoglobin in the body?
A. Transporting oxygen in the blood
B. Facilitating CO2 transport
C. Storing oxygen in muscle tissue
D. Buffering blood pH
Answer: C
Rationale: Myoglobin has a high affinity for oxygen and serves as an oxygen storage unit in
muscle cells.
|WGU
1. Which level of protein structure is characterized by the formation of alpha-
helices and beta-pleated sheets?
A. Primary structure
B. Tertiary structure
C. Secondary structure
D. Quaternary structure
Answer: C
Rationale: Secondary structure refers to local folded structures that form within a
polypeptide due to interactions between atoms of the backbone, specifically hydrogen
bonding.
2. What is the primary function of an enzyme in a biochemical reaction?
A. To decrease the activation energy
B. To increase the Gibbs free energy of the reaction
C. To change the equilibrium constant
D. To be consumed in the reaction
Answer: A
Rationale: Enzymes act as catalysts by lowering the activation energy required for a
reaction to proceed, thereby increasing the rate of the reaction.
,3. In the Michaelis-Menten equation, what does Km represent?
A. The substrate concentration at which velocity is half of Vmax
B. The maximum velocity of the reaction
C. The turnover number
D. The total enzyme concentration
Answer: A
Rationale: Km is the Michaelis constant, which indicates the substrate concentration at
which the reaction rate is 50% of the maximum velocity (Vmax).
4. Which molecule acts as the final electron acceptor in the electron transport
chain during aerobic respiration?
A. NAD+
B. FAD
C. Water
D. Oxygen
Answer: D
Rationale: Oxygen (O2) is the final electron acceptor in the electron transport chain, where
it is reduced to form water.
5. Which enzyme is responsible for unwinding the DNA double helix during
replication?
A. Helicase
B. DNA Ligase
C. DNA Polymerase
D. Primase
Answer: A
Rationale: Helicase is the enzyme that breaks the hydrogen bonds between the base pairs
to unzip the DNA strands.
, 6. What is the result of a nonsense mutation in a DNA sequence?
A. A different amino acid is incorporated into the protein
B. A premature stop codon is introduced
C. The protein sequence remains unchanged
D. The reading frame is shifted
Answer: B
Rationale: A nonsense mutation changes an amino acid codon into a stop codon, leading to
a truncated and usually nonfunctional protein.
7. Which of the following is a characteristic of competitive inhibition?
A. Km is increased
B. Vmax is decreased
C. The inhibitor binds to an allosteric site
D. The inhibitor binds only to the enzyme-substrate complex
Answer: A
Rationale: In competitive inhibition, the inhibitor competes with the substrate for the
active site, effectively increasing the Km while Vmax remains unchanged.
8. What is the primary role of Myoglobin in the body?
A. Transporting oxygen in the blood
B. Facilitating CO2 transport
C. Storing oxygen in muscle tissue
D. Buffering blood pH
Answer: C
Rationale: Myoglobin has a high affinity for oxygen and serves as an oxygen storage unit in
muscle cells.
