Which one of the following statements regarding enzyme inhibition is correct?

Options

A. Competitive inhibition is seen when a substrate competes with an enzyme for binding to an inhibitor protein.
B. Non-competitive inhibitors often bind to the enzyme irreversibly.
C. Non-compeititve inhibtitve of an enzyme can be overcome by adding large amount of substrate.
D. Competitive inhibition is seen when the substrate and the inhibitor compelte the active site on the enzyme

Answer

To determine which statement regarding enzyme inhibition is correct, we will analyze each of the four statements provided.

### Step-by-Step Solution:

1. **Evaluate Statement 1**: "Competitive inhibition is seen when a substrate competes with the enzyme for binding to the inhibitor protein."
- This statement is incorrect. Competitive inhibition occurs when the substrate competes with the inhibitor for the active site of the enzyme, not for binding to an inhibitor protein.

2. **Evaluate Statement 2**: "Non-competitive inhibitors often bind to enzyme irreversibly."
- This statement is also incorrect. Non-competitive inhibitors can bind to the enzyme at a site other than the active site, and their binding is not always irreversible. In many cases, non-competitive inhibition is reversible.

3. **Evaluate Statement 3**: "Non-competitive inhibitor of an enzyme can be overcome by adding a large amount of substrate."
- This statement is incorrect. In non-competitive inhibition, the inhibitor binds to a site other than the active site, and adding more substrate does not reverse the inhibition because the active site remains available.

4. **Evaluate Statement 4**: "Competitive inhibition is seen when a substrate and inhibitor compete for the active site of the enzyme."
- This statement is correct. In competitive inhibition, both the substrate and the inhibitor compete for the same active site on the enzyme. If more substrate is added, it can outcompete the inhibitor for binding to the active site.

### Conclusion:
The correct statement regarding enzyme inhibition is **Statement 4**: "Competitive inhibition is seen when a substrate and inhibitor compete for the active site of the enzyme."

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