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MBBS QUESTION #10319
Question 1
A competitive enzyme inhibitor, which binds reversibly at the enzyme's active site, characteristically produces which kinetic pattern?
  • Increased apparent $K_m$ with unchanged $V_{max}$, since the inhibitory effect can be overcome by sufficiently increasing substrate concentration✔️
  • Decreased $V_{max}$ with unchanged $K_m$
  • Decreased both $K_m$ and $V_{max}$
  • Binding exclusively to the enzyme-substrate complex, never to free enzyme
Correct Answer Explanation
Because a competitive inhibitor competes directly with substrate for the same active site, raising substrate concentration can outcompete the inhibitor, restoring $V_{max}$ at sufficiently high [S] — but more substrate is now needed to reach half-maximal velocity, raising the apparent $K_m$.