Assertion (A) Competitive inhibitors compete with natural substrate for their attachement on the active sites of enzymes.
Reason (R) In competitive inhibitor binds to the allosteric site of the enzyme.

Options

A. If both assertion and reason are true and reason is the correct explanation of assertion .
B. If both assertion and reason are true but reason is not the correct explanation of assertion .
C. If assertion is true but reason is false.
D. If both assertion and reason are false.

Explanation

To solve the assertion and reason question, we will analyze both the assertion (A) and the reason (R) step by step.

### Step 1: Analyze the Assertion (A)
The assertion states: "Competitive inhibitors compete with natural substrate for their attachment on the active sites of enzymes."

- Competitive inhibitors are molecules that resemble the substrate of an enzyme and bind to the active site, preventing the actual substrate from binding. This competition reduces the rate of the reaction because the substrate cannot access the active site when the inhibitor is bound.

**Conclusion for Step 1**: The assertion is true because competitive inhibitors indeed compete with the natural substrate for binding to the active site.

### Step 2: Analyze the Reason (R)
The reason states: "In competitive inhibitors bind to the allosteric site of the enzyme."

- The allosteric site is a different site on the enzyme that is not the active site. In competitive inhibition, the inhibitor binds specifically to the active site, not the allosteric site. Allosteric inhibitors affect enzyme activity by binding to the allosteric site, which can change the shape of the enzyme and affect its function, but this is not the case for competitive inhibitors.

**Conclusion for Step 2**: The reason is false because competitive inhibitors do not bind to the allosteric site; they bind to the active site.

### Final Conclusion
- The assertion (A) is true.
- The reason (R) is false.

Thus, the correct answer is that the assertion is true, but the reason is false.