An enzyme may be rendered inoperative by :

Options

A. adding apoenzyme
B. doubling its concentration
C. blocking its active site
D. Removing byproducts as soon as they are formed

Explanation

**Step-by-Step Solution:**

1. **Understanding Enzymes**: Enzymes are biological catalysts that speed up chemical reactions in the body. They are typically proteins that have a specific region called the active site where substrate molecules bind.

2. **Analyzing the Options**:
- **Option 1: Adding a poenzyme**: A poenzyme refers to an inactive enzyme. Adding it to an active enzyme will not render the active enzyme inoperative. Therefore, this option is incorrect.

- **Option 2: Doubling its concentration**: Increasing the concentration of an enzyme does not make it inoperative. In fact, it may enhance the reaction rate until saturation is reached. Thus, this option is also incorrect.

- **Option 3: Blocking its active site**: The active site is crucial for the enzyme's function. If the active site is blocked, the enzyme cannot bind to its substrate, rendering it inoperative. This option is correct.

- **Option 4: Removing byproducts as soon as they are formed**: The removal of byproducts does not affect the enzyme's ability to function. Byproducts are produced after the enzyme has acted on the substrate, so this option is incorrect.

3. **Conclusion**: The correct answer is that an enzyme may be rendered inoperative by blocking its active site.

**Final Answer**: An enzyme may be rendered inoperative by blocking its active site.

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