Enzyme kinetics – Lineweaver-Burk plot MCQs With Answer

Enzyme kinetics – Lineweaver-Burk plot MCQs With Answer

Understanding enzyme kinetics is essential for B. Pharm students studying drug action and metabolism. The Lineweaver-Burk plot, a double-reciprocal transformation of the Michaelis-Menten equation, helps estimate key parameters like Km and Vmax and distinguish types of enzyme inhibition. Mastery of concepts such as slope (Km/Vmax), x-intercept (−1/Km), and y-intercept (1/Vmax) improves interpretation of enzyme assays, competitive and noncompetitive inhibition, and kinetic data analysis. These MCQs are designed to reinforce theory, calculations, graphical interpretation, and practical implications in pharmacology and drug development. Now let’s test your knowledge with 50 MCQs on this topic.

Q1. What is the primary purpose of using a Lineweaver-Burk plot in enzyme kinetics?

• To linearize Michaelis-Menten data and determine Km and Vmax
• To measure enzyme concentration directly
• To determine pH dependence of enzyme activity
• To calculate molecular weight of enzymes

Correct Answer: To linearize Michaelis-Menten data and determine Km and Vmax

Q2. The Lineweaver-Burk plot is a graph of which variables?

• 1/V versus 1/[S]
• V versus [S]
• ln V versus ln [S]
• V versus ln [S]

Correct Answer: 1/V versus 1/[S]

Q3. On a Lineweaver-Burk plot, the y-intercept corresponds to:

• 1/Vmax
• −1/Km
• Km/Vmax
• Vmax

Correct Answer: 1/Vmax

Q4. On the Lineweaver-Burk plot the x-intercept equals:

• −1/Km
• 1/Km
• −Km
• 1/Vmax

Correct Answer: −1/Km

Q5. The slope of the Lineweaver-Burk plot is:

• Km/Vmax
• Vmax/Km
• 1/Km
• Km × Vmax

Correct Answer: Km/Vmax

Q6. Which type of inhibition increases the apparent Km but does not change Vmax on the Lineweaver-Burk plot?

• Competitive inhibition
• Noncompetitive inhibition
• Uncompetitive inhibition
• Mixed inhibition

Correct Answer: Competitive inhibition

Q7. How does pure noncompetitive inhibition appear on a Lineweaver-Burk plot?

• Same x-intercept, increased y-intercept
• Leftward x-intercept shift, unchanged y-intercept
• Parallel lines with decreased intercepts
• Lower slope with same intercepts

Correct Answer: Same x-intercept, increased y-intercept

Q8. Uncompetitive inhibition on a Lineweaver-Burk plot causes:

• Parallel lines with both intercepts changed
• Intersection at same y-intercept
• Rightward x-intercept shift only
• No change in slope

Correct Answer: Parallel lines with both intercepts changed

Q9. Which of the following is a disadvantage of the Lineweaver-Burk plot?

• It overemphasizes errors at low substrate concentrations
• It cannot linearize Michaelis-Menten data
• It gives direct Vmax without calculation
• It is insensitive to inhibition types

Correct Answer: It overemphasizes errors at low substrate concentrations

Q10. If 1/Vmax equals 0.2 min/μmol, what is Vmax?

• 5 μmol/min
• 0.2 μmol/min
• 0.05 μmol/min
• 2 μmol/min

Correct Answer: 5 μmol/min

Q11. Which alternative plot reduces weighting of errors at low [S] compared to Lineweaver-Burk?

• Hanes-Woolf plot
• Scatchard plot
• Semi-log plot
• Arrhenius plot

Correct Answer: Hanes-Woolf plot

Q12. In a Lineweaver-Burk plot, two lines intersecting on the x-axis implies which effect?

• Noncompetitive inhibition
• Competitive inhibition
• Uncompetitive inhibition
• No inhibition

Correct Answer: Competitive inhibition

Q13. For a Michaelis-Menten enzyme, the double reciprocal transformation is given by which equation?

• 1/V = (Km/Vmax)(1/[S]) + 1/Vmax
• V = Vmax[S]/(Km + [S])
• ln V = ln Vmax − (Km/[S])
• V = Km + Vmax/[S]

Correct Answer: 1/V = (Km/Vmax)(1/[S]) + 1/Vmax

Q14. If Km = 2 mM and Vmax = 100 μmol/min, what is the slope of the Lineweaver-Burk plot?

• 0.02 min/mM·μmol
• 0.02 mM/μmol·min
• 0.02 mM·min/μmol
• 0.02 min/μmol

Correct Answer: 0.02 mM/μmol·min

Q15. Why is Lineweaver-Burk plot still taught despite its limitations?

• It provides straightforward visual differentiation of inhibition types
• It is the most accurate method for parameter estimation
• It does not require reciprocal transformation
• It eliminates experimental error

Correct Answer: It provides straightforward visual differentiation of inhibition types

Q16. On Lineweaver-Burk, mixed inhibition generally results in:

• Change in both slope and intercepts with intersection not on axes
• Parallel lines
• Same slope, different y-intercepts
• Same x-intercept only

Correct Answer: Change in both slope and intercepts with intersection not on axes

Q17. The Lineweaver-Burk plot is particularly sensitive to experimental error at which substrate concentration range?

• Low [S]
• High [S]
• Intermediate [S]
• All equally

Correct Answer: Low [S]

Q18. Which kinetic parameter describes substrate concentration at half Vmax?

• Km
• Vmax
• kcat
• kcat/Km

Correct Answer: Km

Q19. In enzyme kinetics, kcat equals:

• Vmax/[E]t
• Km/Vmax
• 1/Km
• Vmax × Km

Correct Answer: Vmax/[E]t

Q20. When plotting Lineweaver-Burk, what is plotted on the y-axis?

• 1/velocity (1/V)
• Velocity (V)
• Substrate concentration [S]
• ln[velocity]

Correct Answer: 1/velocity (1/V)

Q21. If two Lineweaver-Burk lines intersect left of the y-axis and above the x-axis, this suggests:

• Mixed inhibition
• Pure competitive inhibition
• Pure noncompetitive inhibition
• No inhibition

Correct Answer: Mixed inhibition

Q22. Which plot uses V versus V/[S] and is an alternative linearization of the Michaelis-Menten equation?

• Eadie-Hofstee plot
• Lineweaver-Burk plot
• Hanes-Woolf plot
• Dixon plot

Correct Answer: Eadie-Hofstee plot

Q23. The Dixon plot is primarily used to determine:

• Inhibition constant Ki
• Vmax only
• Km only
• Enzyme turnover number

Correct Answer: Inhibition constant Ki

Q24. In competitive inhibition, what happens to the Lineweaver-Burk slope?

• Slope increases (Km/Vmax increases)
• Slope decreases
• Slope remains unchanged
• Slope becomes zero

Correct Answer: Slope increases (Km/Vmax increases)

Q25. For uncompetitive inhibition, how are Km and Vmax affected?

• Both apparent Km and Vmax decrease proportionally
• Km increases, Vmax unchanged
• Km unchanged, Vmax decreases
• Both increase

Correct Answer: Both apparent Km and Vmax decrease proportionally

Q26. Which of the following statements about Km is correct?

• Km is the substrate concentration at which velocity is half of Vmax
• Km equals Vmax at saturating substrate
• Km is independent of enzyme affinity
• Km is the maximum reaction velocity

Correct Answer: Km is the substrate concentration at which velocity is half of Vmax

Q27. If a Lineweaver-Burk plot y-intercept increases in presence of inhibitor while x-intercept remains same, the inhibitor is likely:

• Noncompetitive
• Competitive
• Uncompetitive
• Activating agent

Correct Answer: Noncompetitive

Q28. Which transformation exaggerates data error the most when creating a Lineweaver-Burk plot?

• Reciprocal of small velocities
• Logarithm of rates
• Square root of substrate
• Direct plotting of V vs [S]

Correct Answer: Reciprocal of small velocities

Q29. The intercept form of the Lineweaver-Burk equation allows direct readout of:

• 1/Vmax and −1/Km
• Vmax and Km directly
• kcat only
• Enzyme concentration

Correct Answer: 1/Vmax and −1/Km

Q30. In the presence of a competitive inhibitor, how can increasing substrate concentration affect reaction velocity?

• It can overcome inhibition to reach Vmax
• It decreases Vmax permanently
• It converts inhibition to noncompetitive type
• It has no effect on velocity

Correct Answer: It can overcome inhibition to reach Vmax

Q31. Which parameter combination increases slope of Lineweaver-Burk but leaves x-intercept unchanged?

• Increase in 1/Vmax with same −1/Km (noncompetitive)
• Decrease in Km only
• Increase in Km only (competitive)
• Decrease in both Km and Vmax proportionally

Correct Answer: Increase in 1/Vmax with same −1/Km (noncompetitive)

Q32. When plotting reciprocal values, why is accuracy of Vmax estimation often poor?

• Because small errors at low velocities are amplified by reciprocals
• Because reciprocals convert linearity to nonlinearity
• Because Vmax is not in the Lineweaver-Burk equation
• Because substrate concentration is not measured

Correct Answer: Because small errors at low velocities are amplified by reciprocals

Q33. Which of the following is true for a Lineweaver-Burk plot of a simple Michaelis-Menten enzyme without inhibitors?

• Single straight line intercepting axes at defined points
• Multiple parallel lines depending on [S]
• Curved line similar to Michaelis-Menten
• No intercept on axes

Correct Answer: Single straight line intercepting axes at defined points

Q34. A student obtains a Lineweaver-Burk slope of 0.04 and y-intercept 0.01 (units 1/V). What is Vmax?

• 100 units
• 10 units
• 0.01 units
• 40 units

Correct Answer: 100 units

Q35. Which kinetic plot places less emphasis on low [S] errors than Lineweaver-Burk and plots [S]/V vs [S]?

• Hanes-Woolf plot
• Dixon plot
• Scatchard plot
• Arrhenius plot

Correct Answer: Hanes-Woolf plot

Q36. In Lineweaver-Burk analysis, a higher Km indicates:

• Lower affinity of enzyme for substrate
• Higher affinity of enzyme for substrate
• Faster turnover number
• Greater enzyme concentration

Correct Answer: Lower affinity of enzyme for substrate

Q37. For competitive inhibition, how do Lineweaver-Burk lines at different inhibitor concentrations intersect?

• At the y-axis (same 1/Vmax), crossing at the same y-intercept
• Parallel without intersection
• At the x-axis only
• Nowhere, they are identical

Correct Answer: At the y-axis (same 1/Vmax), crossing at the same y-intercept

Q38. If an inhibitor reduces Vmax but decreases Km as well, which inhibition type is suggested?

• Uncompetitive inhibition
• Competitive inhibition
• Pure noncompetitive inhibition
• No inhibition

Correct Answer: Uncompetitive inhibition

Q39. Why might one prefer nonlinear regression over Lineweaver-Burk for parameter estimation?

• Nonlinear regression fits raw data without reciprocal transformation and yields better estimates
• Nonlinear regression is simpler to plot by hand
• Nonlinear regression ignores experimental error
• Nonlinear regression always gives higher Km

Correct Answer: Nonlinear regression fits raw data without reciprocal transformation and yields better estimates

Q40. Which experimental practice reduces Lineweaver-Burk error amplification?

• Accurate measurement of low velocities and replicates at low [S]
• Avoid measuring at low [S] entirely
• Only use single high [S] data point
• Use logarithmic scaling of axes

Correct Answer: Accurate measurement of low velocities and replicates at low [S]

Q41. The Lineweaver-Burk plot of an enzyme inhibited irreversibly would most likely show:

• Decreased Vmax without recovery on dilution
• Classic competitive pattern with same Vmax
• Parallel lines characteristic of uncompetitive inhibition
• Increased Vmax

Correct Answer: Decreased Vmax without recovery on dilution

Q42. Which parameter is NOT directly obtained from a Lineweaver-Burk plot?

• kcat/Km (requires enzyme concentration and kcat)
• 1/Vmax
• −1/Km
• Slope (Km/Vmax)

Correct Answer: kcat/Km (requires enzyme concentration and kcat)

Q43. In practice, which computational method is recommended over Lineweaver-Burk to minimize error biases?

• Nonlinear least-squares regression of the Michaelis-Menten equation
• Manual reciprocal plotting
• Graphical estimation from double-reciprocal plot only
• Taking logarithms of velocity

Correct Answer: Nonlinear least-squares regression of the Michaelis-Menten equation

Q44. Which statement best describes the effect of a reversible competitive inhibitor on Km and Vmax?

• Apparent Km increases while Vmax remains unchanged
• Km decreases and Vmax increases
• Both Km and Vmax decrease
• Km unchanged and Vmax decreases

Correct Answer: Apparent Km increases while Vmax remains unchanged

Q45. When using Lineweaver-Burk plots for teaching, what concept is most effectively illustrated?

• How different inhibition types alter Km and Vmax graphically
• Exact numerical determination of kcat in all cases
• pH dependence of enzymatic activity
• Protein tertiary structure

Correct Answer: How different inhibition types alter Km and Vmax graphically

Q46. If the Lineweaver-Burk slope doubles while y-intercept remains constant, what could be happening?

• Apparent Km doubled while Vmax unchanged (possible competitive inhibition)
• Vmax halved but Km unchanged
• Both Km and Vmax halved proportionally
• Measurement error only

Correct Answer: Apparent Km doubled while Vmax unchanged (possible competitive inhibition)

Q47. In a Lineweaver-Burk plot, if two inhibitor concentrations create lines that intersect above the x-axis and to the left of the y-axis, this most likely indicates:

• Mixed inhibition with different effects on Km and Vmax
• Pure competitive inhibition
• Pure uncompetitive inhibition
• No effect of inhibitor

Correct Answer: Mixed inhibition with different effects on Km and Vmax

Q48. Which practical tip improves reliability of Lineweaver-Burk derived parameters?

• Use many substrate concentrations, including replicates at low and high [S]
• Use only two data points to draw the line
• Exclude replicate measurements
• Avoid measuring initial rates

Correct Answer: Use many substrate concentrations, including replicates at low and high [S]

Q49. The reciprocal transformation used in Lineweaver-Burk is particularly useful for:

• Visually distinguishing types of reversible inhibition
• Eliminating measurement error completely
• Measuring enzyme molecular weight
• Directly calculating kcat without enzyme concentration

Correct Answer: Visually distinguishing types of reversible inhibition

Q50. Which conclusion is correct when Lineweaver-Burk lines for increasing inhibitor concentrations converge at a single point left of the y-axis?

• Evidence for mixed inhibition where both Km and Vmax are affected
• Pure competitive inhibition only
• Uncompetitive inhibition only
• No inhibition present

Correct Answer: Evidence for mixed inhibition where both Km and Vmax are affected

G S Sachin

I am a Registered Pharmacist under the Pharmacy Act, 1948, and the founder of PharmacyFreak.com. I hold a Bachelor of Pharmacy degree from Rungta College of Pharmaceutical Science and Research. With a strong academic foundation and practical knowledge, I am committed to providing accurate, easy-to-understand content to support pharmacy students and professionals. My aim is to make complex pharmaceutical concepts accessible and useful for real-world application.

Mail- Sachin@pharmacyfreak.com