More Questions from Enzymes and Kinetics

The Michaelis–Menten relationship can be expressed in several algebraically equivalent linear forms used for plotting. Which statement correctly summarizes these alternative forms?

Biochemical Engineering Enzymes and Kinetics Difficulty: Medium
Choose an option
  • A
    1/r = (1/rmax) + (Km / (rmax * Cs))   [Lineweaver–Burk]
  • B
    Cs/r = (Cs/rmax) + (Km/rmax)   [Hanes–Woolf]
  • C
    r = rmax - (Km * r / Cs)   [Eadie–Hofstee]
  • D
    All of these
  • E
    None of these forms is equivalent to Michaelis–Menten

Answer

Correct Answer: All of these

Explanation

Introduction / Context:Although the canonical Michaelis–Menten equation v = (Vmax * [S]) / (Km + [S]) is nonlinear, several linear rearrangements facilitate parameter estimation and diagnostic plotting. Three classic forms are Lineweaver–Burk, Hanes–Woolf, and Eadie–Hofstee.

Given Data / Assumptions:

  • Symbols: r (or v) for rate, Cs (or [S]) for substrate, rmax (or Vmax) for maximum rate.
  • Steady-state, initial-rate conditions apply.
  • Algebraic rearrangements preserve equivalence if performed correctly.

Concept / Approach:Demonstrate each rearrangement starting from r = (rmax * Cs) / (Km + Cs) and show equivalence to one of the standard plotting lines.

Step-by-Step Solution:

Lineweaver–Burk: Take reciprocals → 1/r = (Km + Cs)/(rmax * Cs) = (1/rmax) + (Km/(rmax * Cs)).Hanes–Woolf: Multiply both sides by (Km + Cs)/r → Cs/r = (Cs/rmax) + (Km/rmax).Eadie–Hofstee: Multiply both sides by (Km + Cs)/Cs → r = rmax - (Km * r / Cs).All three are algebraically equivalent to the original Michaelis–Menten expression.

Verification / Alternative check:Fitting the same data with these transformations yields identical parameter values in the absence of error; differences in practice reflect error-weighting, not algebraic inequivalence.

Why Other Options Are Wrong:

  • Each individual linear form is valid; therefore “None of these” is incorrect.

Common Pitfalls:Confusing sign conventions or mixing symbols; ensure r corresponds to v and Cs to [S]. Also note that linearizations can distort error structure; modern practice often fits the untransformed nonlinear model.

Final Answer:All of these

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