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MBBS QUESTION #10321
Question 1
On a Lineweaver-Burk (double-reciprocal) plot of $\dfrac{1}{v}$ versus $\dfrac{1}{[S]}$, which pattern distinguishes competitive from non-competitive inhibition?
  • Competitive inhibition changes the y-intercept ($1/V_{max}$) but leaves the x-intercept unchanged
  • Competitive inhibition leaves the y-intercept ($1/V_{max}$) unchanged but shifts the x-intercept (reflecting an increased apparent $K_m$); non-competitive inhibition instead raises the y-intercept while leaving the x-intercept unchanged✔️
  • Both types of inhibition produce visually identical Lineweaver-Burk plots
  • Non-competitive inhibition changes only the x-intercept, never the y-intercept
Correct Answer Explanation
On a Lineweaver-Burk plot, competitive inhibitors share the same y-intercept ($1/V_{max}$ unchanged) as uninhibited enzyme but show a less negative x-intercept (increased $K_m$); non-competitive inhibitors instead raise the y-intercept ($V_{max}$ reduced) while the x-intercept ($K_m$) stays fixed — a classic way to distinguish inhibitor type experimentally.