In the context of enzyme kinetics, if the concentration of a substrate $[S]$ is significantly lower than the Michaelis constant $K_m$, what is the approximate order of the reaction?

Solution

1. The Michaelis-Menten equation is given by $v=\frac{V_{max}[S]}{K_m+[S]}$.
2. When $[S]\ll K_m$, the denominator $K_m+[S]$ is approximately equal to $K_m$.
3. The equation simplifies to $v\approx \frac{V_{max}}{K_m}[S]$.
4. Since $v$ is directly proportional to $[S{]}^1$, the reaction follows first-order kinetics.
5. Hence the answer is (B).