![21. An enzymatic reaction exhibits Michaelis-Menten kinetics. For this reaction, on doubling the concentration of enzyme while maintaining [S] >> [E0], (a) Both Km and Vmax will remain the same. (b) Km will remain the same but Vmax will increase. (c) Km will increase but Vmax will remain the same.](https://www.letstalkacademy.com/wp-content/uploads/2026/01/slide_21-14.png)
21. An enzymatic reaction exhibits Michaelis–Menten kinetics. For this reaction, on doubling the
concentration of enzyme while maintaining [S] >> [E0],
(a) Both Km and Vmax will remain the same.
(b) Km will remain the same but Vmax will increase.
(c) Km will increase but Vmax will remain the same.
In Michaelis-Menten kinetics, enzymatic reactions follow the equation:
v = (Vmax[S]) / (Km + [S])
where v is initial velocity, Vmax is maximum velocity, Km is the Michaelis constant, and [S] is substrate concentration. Doubling enzyme concentration ([E0]) while keeping [S] >> [E0] affects these parameters predictably under standard assumptions. The correct answer is option (b): Km remains the same, but Vmax increases.
Core Concepts
Vmax = kcat[E0], so Vmax scales directly with total enzyme concentration. Doubling [E0] doubles Vmax, as more enzyme molecules allow faster product formation at saturation.
Km = (k−1 + kcat) / k1, reflecting enzyme-substrate affinity and remains unchanged by [E0], since it depends only on rate constants.
Experimental Implications
At high [S], velocity approximates Vmax, so doubling [E0] doubles observed rate without altering Km from Lineweaver-Burk plots. This is critical in scaling bioreactor reactions in biotechnology.
Advanced Notes for Biotech Learners
While classical theory assumes Km independence, deviations arise if [E0] becomes comparable to [S], violating quasi-steady-state assumptions. Here, [S] >> [E0] validates standard kinetics, common in fermentation and enzyme assays.
