Effect of Vmax and Km in competitive inhibition is as follows
**Core Concept**
Competitive inhibition is a type of enzyme inhibition where an inhibitor binds to the active site of the enzyme, thereby reducing its activity. The maximum velocity (Vmax) of an enzyme-catalyzed reaction and the Michaelis constant (Km) are key parameters that are affected by competitive inhibition. In this context, Vmax is the maximum rate of the reaction, while Km is the substrate concentration at which the reaction rate is half of Vmax.
**Why the Correct Answer is Right**
In competitive inhibition, the inhibitor competes with the substrate for binding to the active site of the enzyme. As a result, the Vmax of the reaction remains unchanged, but the Km increases. This is because the inhibitor increases the apparent Km by shifting the curve to the right, indicating that more substrate is required to achieve half of the maximum velocity. The enzyme is still able to reach its maximum velocity, but it requires a higher substrate concentration to do so.
**Why Each Wrong Option is Incorrect**
* **Option A:** This option is incorrect because competitive inhibition does not decrease the Vmax of the reaction. Instead, it increases the Km, allowing the enzyme to reach its maximum velocity at a higher substrate concentration.
* **Option B:** This option is incorrect because non-competitive inhibition would decrease the Vmax of the reaction, but not increase the Km.
* **Option C:** This option is incorrect because uncompetitive inhibition would decrease both the Vmax and Km of the reaction.
**Clinical Pearl / High-Yield Fact**
Remember that competitive inhibition is reversible and can be overcome by increasing the substrate concentration. This is in contrast to non-competitive inhibition, which is irreversible and cannot be overcome by increasing the substrate concentration.
**Correct Answer: A. Competitive inhibition increases Km without changing Vmax.**