In case of competitive inhibition of an enzyme,

Options

A. `V_("max")` is increased
B. `k_(m)` increased
C. Extent of inhibition remains the same in high substrate concentrations
D. None of the above

Answer

To understand competitive inhibition of an enzyme, let's break down the concepts step by step.

### Step-by-Step Solution:

1. **Understanding Enzyme Inhibition**:
- Enzymes are biological catalysts that speed up chemical reactions. They can be inhibited by various molecules that interfere with their activity.

2. **Types of Inhibition**:
- There are three main types of enzyme inhibition: competitive, uncompetitive, and non-competitive inhibition.
- In competitive inhibition, an inhibitor competes with the substrate for binding to the active site of the enzyme.

3. **Effect on Km and Vmax**:
- **Km (Michaelis-Menten constant)**: This is a measure of the substrate concentration required to reach half of Vmax. In competitive inhibition, the presence of the inhibitor increases the Km value because a higher concentration of substrate is needed to outcompete the inhibitor for binding to the active site.
- **Vmax (maximum velocity)**: This is the maximum rate of the reaction when the enzyme is saturated with substrate. In competitive inhibition, Vmax remains unchanged because, at sufficiently high substrate concentrations, the effect of the inhibitor can be overcome.

4. **Conclusion**:
- In competitive inhibition, Km is increased (indicating a decrease in affinity for the substrate), while Vmax remains unaffected. Therefore, the correct answer to the question is that in competitive inhibition, Km is increased and Vmax is unaffected.

### Final Answer:
- **Km is increased, Vmax is unaffected.**