BioChem 210 Module 5 Exam - Enzymes and Kinetics 2026 Geneva
College
1. What is the primary function of an enzyme in a biological reaction?
A. To increase the equilibrium constant of the reaction
B. To decrease the activation energy of the reaction
C. To provide energy to drive an endergonic reaction
D. To increase the change in Gibbs free energy (ΔG)
Answer: B
Rationale: Enzymes act as catalysts by lowering the activation energy barrier, allowing the
reaction to proceed faster without changing the equilibrium or the ΔG.
2. Which of the following models suggests that the enzyme’s active site changes
shape slightly to fit the substrate?
A. Lock and Key Model
B. Fluid Mosaic Model
C. Concerted Model
D. Induced Fit Model
Answer: D
Rationale: The Induced Fit Model suggests that the binding of the substrate induces a
conformational change in the enzyme to improve the fit.
,3. What does the Michaelis constant (Km) represent?
A. The maximum velocity of the reaction
B. The total concentration of enzyme present in the reaction
C. The substrate concentration at which the reaction velocity is half of Vmax
D. The rate constant for the formation of the product
Answer: C
Rationale: Km is defined as the substrate concentration [S] where the initial velocity (v) is
equal to 1/2 Vmax.
4. In a Lineweaver-Burk plot, what does the y-intercept represent?
A. 1/Vmax
B. -1/Km
C. 1/Km
D. Vmax/Km
Answer: A
Rationale: The Lineweaver-Burk plot is a double reciprocal plot where the y-intercept is
1/Vmax and the x-intercept is -1/Km.
5. A competitive inhibitor affects which kinetic parameter of an enzyme?
A. It increases Vmax
B. It decreases Km
C. It decreases Vmax
D. It increases the apparent Km
Answer: D
Rationale: Competitive inhibitors compete with the substrate for the active site, requiring
more substrate to reach 1/2 Vmax, thus increasing the apparent Km while Vmax remains
unchanged.
, 6. Which type of inhibition cannot be overcome by increasing the substrate
concentration?
A. Competitive Inhibition
B. Reversible Inhibition
C. Non-competitive Inhibition
D. Allosteric Activation
Answer: C
Rationale: Non-competitive inhibitors bind to a site other than the active site, reducing the
enzyme’s turnover number (Vmax) regardless of substrate concentration.
7. What is the kcat of an enzyme?
A. The Michaelis constant
B. The affinity of the enzyme for its substrate
C. The turnover number, representing the number of substrate molecules converted to product per unit time
D. The slope of the Lineweaver-Burk plot
Answer: C
Rationale: kcat, or the turnover number, measures the catalytic activity of a single enzyme
molecule when it is fully saturated with substrate.
8. Which of the following describes an apoenzyme?
A. An enzyme with its required cofactor attached
B. An RNA molecule with catalytic activity
C. The protein portion of an enzyme that requires a cofactor but lacks it
D. An enzyme that has been irreversibly denatured
Answer: C
Rationale: An apoenzyme is the inactive protein part of an enzyme. Once the
cofactor/coenzyme is added, it becomes a functional holoenzyme.
College
1. What is the primary function of an enzyme in a biological reaction?
A. To increase the equilibrium constant of the reaction
B. To decrease the activation energy of the reaction
C. To provide energy to drive an endergonic reaction
D. To increase the change in Gibbs free energy (ΔG)
Answer: B
Rationale: Enzymes act as catalysts by lowering the activation energy barrier, allowing the
reaction to proceed faster without changing the equilibrium or the ΔG.
2. Which of the following models suggests that the enzyme’s active site changes
shape slightly to fit the substrate?
A. Lock and Key Model
B. Fluid Mosaic Model
C. Concerted Model
D. Induced Fit Model
Answer: D
Rationale: The Induced Fit Model suggests that the binding of the substrate induces a
conformational change in the enzyme to improve the fit.
,3. What does the Michaelis constant (Km) represent?
A. The maximum velocity of the reaction
B. The total concentration of enzyme present in the reaction
C. The substrate concentration at which the reaction velocity is half of Vmax
D. The rate constant for the formation of the product
Answer: C
Rationale: Km is defined as the substrate concentration [S] where the initial velocity (v) is
equal to 1/2 Vmax.
4. In a Lineweaver-Burk plot, what does the y-intercept represent?
A. 1/Vmax
B. -1/Km
C. 1/Km
D. Vmax/Km
Answer: A
Rationale: The Lineweaver-Burk plot is a double reciprocal plot where the y-intercept is
1/Vmax and the x-intercept is -1/Km.
5. A competitive inhibitor affects which kinetic parameter of an enzyme?
A. It increases Vmax
B. It decreases Km
C. It decreases Vmax
D. It increases the apparent Km
Answer: D
Rationale: Competitive inhibitors compete with the substrate for the active site, requiring
more substrate to reach 1/2 Vmax, thus increasing the apparent Km while Vmax remains
unchanged.
, 6. Which type of inhibition cannot be overcome by increasing the substrate
concentration?
A. Competitive Inhibition
B. Reversible Inhibition
C. Non-competitive Inhibition
D. Allosteric Activation
Answer: C
Rationale: Non-competitive inhibitors bind to a site other than the active site, reducing the
enzyme’s turnover number (Vmax) regardless of substrate concentration.
7. What is the kcat of an enzyme?
A. The Michaelis constant
B. The affinity of the enzyme for its substrate
C. The turnover number, representing the number of substrate molecules converted to product per unit time
D. The slope of the Lineweaver-Burk plot
Answer: C
Rationale: kcat, or the turnover number, measures the catalytic activity of a single enzyme
molecule when it is fully saturated with substrate.
8. Which of the following describes an apoenzyme?
A. An enzyme with its required cofactor attached
B. An RNA molecule with catalytic activity
C. The protein portion of an enzyme that requires a cofactor but lacks it
D. An enzyme that has been irreversibly denatured
Answer: C
Rationale: An apoenzyme is the inactive protein part of an enzyme. Once the
cofactor/coenzyme is added, it becomes a functional holoenzyme.
