In competitive inhibition, the relation Km and Vmax is one of the following
**Core Concept**
Competitive inhibition is a type of enzyme inhibition where an inhibitor molecule structurally resembles the substrate and binds to the active site, reducing the enzyme's ability to bind to the substrate. This leads to an increase in the Km (Michaelis constant) without affecting the Vmax (maximum velocity) of the enzyme.
**Why the Correct Answer is Right**
In competitive inhibition, the inhibitor competes with the substrate for binding to the active site. As a result, the enzyme requires a higher substrate concentration to achieve half-maximal velocity (Km increases), but the maximum velocity (Vmax) remains unchanged. This is because the inhibitor does not affect the enzyme's catalytic activity, only its ability to bind to the substrate.
**Why Each Wrong Option is Incorrect**
* **Option A:** Incorrect because competitive inhibition does not decrease Km; instead, it increases Km by requiring a higher substrate concentration to achieve half-maximal velocity.
* **Option B:** Incorrect because competitive inhibition does not decrease Vmax; instead, Vmax remains unchanged since the inhibitor does not affect the enzyme's catalytic activity.
* **Option C:** Incorrect because competitive inhibition does not increase Km and decrease Vmax simultaneously; instead, Km increases, and Vmax remains unchanged.
**Clinical Pearl / High-Yield Fact**
It's essential to remember that competitive inhibition can be overcome by increasing the substrate concentration, which can lead to a significant increase in enzyme activity. This is why competitive inhibitors are often used as drugs, as they can be titrated to achieve a desired therapeutic effect.
**Correct Answer:** C. Km increases, Vmax remains unchanged