Assertion `: beta-` pleated sheet structure of protein shows maximum extension.
Reason `:` Intermolecular hydrogen bonding is present in them.

Options

A. If both assertion & Reason are true & the Reason is a correct explanation of the Assertion
B. If both Assertion & Reason a True but Reason is not a correct explantation of the Assertion
C. If Assertion is True but the Reason is False
D. If both Assertion & Reason are false

Answer

To analyze the given assertion and reason, let's break down the concepts step by step:

### Step-by-Step Solution:

1. **Understanding Protein Structure**:
- Proteins have different levels of structure: primary, secondary, tertiary, and quaternary.
- The secondary structure includes two main forms: alpha helix and beta pleated sheet.

**Hint**: Remember the four levels of protein structure and focus on the secondary structure for this question.

2. **Beta Pleated Sheet Structure**:
- The beta pleated sheet is a type of secondary structure where strands of amino acids are arranged in parallel or antiparallel configurations, forming a sheet-like structure.
- This structure allows for maximum extension compared to other forms, such as the alpha helix.

**Hint**: Visualize the beta pleated sheet as a flat sheet formed by multiple strands, which helps in understanding its extended nature.

3. **Role of Hydrogen Bonding**:
- The stability of the beta pleated sheet is largely due to intermolecular hydrogen bonds that form between the carbonyl oxygen of one amino acid and the amide hydrogen of another.
- These hydrogen bonds contribute to the overall structure and stability of the beta pleated sheet.

**Hint**: Focus on how hydrogen bonds contribute to the formation and stability of protein structures.

4. **Evaluating the Assertion**:
- The assertion states that the beta pleated sheet structure shows maximum extension. This is correct because the arrangement of the strands allows for a more extended configuration.

**Hint**: Confirm that the assertion is true based on the structural characteristics of the beta pleated sheet.

5. **Evaluating the Reason**:
- The reason states that intermolecular hydrogen bonding is present in beta pleated sheets. While this is true, it does not fully explain why the beta pleated sheet has maximum extension.
- The extension is more influenced by the size of the R groups of the amino acids involved, which can vary.

**Hint**: Consider whether the reason adequately supports the assertion. In this case, it does not fully explain the assertion.

6. **Conclusion**:
- Both the assertion and the reason are correct statements, but the reason does not correctly explain the assertion. Therefore, the correct answer is that both are true, but the reason is not a valid explanation for the assertion.

### Final Answer:
- Both the assertion and reason are correct, but the reason does not correctly explain the assertion.

### Summary:
- Assertion: True
- Reason: True, but not a valid explanation for the assertion.