Which of the following is not correct regarding competitive inhibition?

Options

A. The inhibitor closely resembles the substrate in its molecules and inhibits the activity of the enzyme.
B. They cannot be used to control bacterial pathogens.
C. Inhibition of succinic dehydrogenase by malonate which closely resembles the substance succinate in structure is an example of it.
D. Substrate cannot bind in such type of inhibition thus enzyme activity declines.

Answer

To solve the question regarding competitive inhibition, let's break down the concepts step by step.

### Step-by-Step Solution

1. **Understanding Enzymes and Substrates**:
- Enzymes are biological catalysts that speed up chemical reactions by binding to substrates. When a substrate binds to an enzyme, it forms an enzyme-substrate complex, leading to the formation of products.

**Hint**: Remember that enzymes facilitate reactions by interacting with substrates.

2. **What is Competitive Inhibition?**:
- Competitive inhibition occurs when an inhibitor, which resembles the substrate's structure, competes with the substrate for binding to the active site of the enzyme. If the inhibitor binds to the enzyme, the substrate cannot bind, leading to decreased enzymatic activity.

**Hint**: Think of competitive inhibitors as "pretenders" that mimic the substrate to block the real substrate from binding.

3. **Analyzing the Options**:
- **Option A**: The inhibitor closely resembles the substrate in its molecules and inhibits the activity of the enzyme.
- This statement is correct because competitive inhibitors are designed to mimic the substrate.

- **Option B**: They cannot be used to control bacterial pathogens.
- This statement is incorrect. Competitive inhibitors can indeed be used to control bacterial pathogens by inhibiting essential bacterial enzymes.

- **Option C**: Inhibition of succinic dehydrogenase by malonate, which closely resembles the substrate succinate in structure, is an example of it.
- This statement is correct as malonate is a known competitive inhibitor of succinate.

- **Option D**: Substrate cannot bind in such type of inhibition; thus, enzymatic activity declines.
- This statement is misleading. While the presence of the inhibitor reduces the likelihood of substrate binding, it does not mean that substrate binding is impossible; it just competes for the active site.

4. **Conclusion**:
- The incorrect statement regarding competitive inhibition is **Option B**, as it incorrectly states that competitive inhibitors cannot be used to control bacterial pathogens.

### Final Answer:
**Option B** is the incorrect statement regarding competitive inhibition.