The Michaelis–Menten relationship can be expressed in several algebraically equivalent linear forms used for plotting. Which statement correctly summarizes these alternative forms?
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A1/r = (1/rmax) + (Km / (rmax * Cs)) [Lineweaver–Burk]
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BCs/r = (Cs/rmax) + (Km/rmax) [Hanes–Woolf]
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Cr = rmax - (Km * r / Cs) [Eadie–Hofstee]
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DAll of these
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ENone 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