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MBBS QUESTION #10318
Question 1
Using the Michaelis-Menten equation $v = \dfrac{V_{max}[S]}{K_m + [S]}$, the Michaelis constant ($K_m$) of an enzyme represents:
  • The maximum possible reaction velocity achievable at saturating substrate
  • The substrate concentration at which reaction velocity is exactly half of $V_{max}$, serving as an inverse measure of enzyme-substrate affinity✔️
  • The total enzyme concentration present in the reaction
  • The equilibrium constant of the overall catalyzed reaction
Correct Answer Explanation
$K_m$ is the substrate concentration giving half-maximal velocity; a low $K_m$ indicates high enzyme-substrate affinity (half-maximal rate reached at low substrate concentration), while a high $K_m$ indicates lower affinity — a key parameter for comparing isoenzymes and predicting drug/substrate behavior.