Enzyme succinic dehydrogenase closely resembles the structure of------------- which acts as a competitive inhibitor of it.

Options

A. malonate
B. oxaloacetate
C. `alpha`-ketoglutarate
D. malate

Explanation

To solve the question regarding the enzyme succinic dehydrogenase and its competitive inhibitor, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Role of Succinic Dehydrogenase**:
- Succinic dehydrogenase is an enzyme that plays a crucial role in the Krebs cycle (also known as the citric acid cycle). Its primary function is to catalyze the conversion of succinate to fumarate.

2. **Identify the Concept of Competitive Inhibition**:
- Competitive inhibitors are molecules that closely resemble the substrate of an enzyme. They compete with the substrate for binding to the active site of the enzyme, thereby inhibiting the enzyme's activity.

3. **Recall the Structure of the Substrate**:
- The substrate for succinic dehydrogenase is succinate. For a competitive inhibitor to effectively inhibit this enzyme, it must have a similar structure to succinate.

4. **Determine the Competitive Inhibitor**:
- The competitive inhibitor that closely resembles succinate is malonate. Malonate has a similar structure, allowing it to bind to the active site of succinic dehydrogenase and inhibit its function.

5. **Conclude the Answer**:
- Therefore, the component that closely resembles the structure of succinic dehydrogenase and acts as a competitive inhibitor is **malonate**.

### Final Answer:
The enzyme succinic dehydrogenase closely resembles the structure of **malonate**, which acts as a competitive inhibitor of it.

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