[A]: Sulphur stabilizes protein structure.
[R]: It does not participate in metabolic pro- cesses

Options

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

Answer

**Step-by-Step Solution:**

1. **Understanding the Assertion (A)**:
- The assertion states that "Sulphur stabilizes protein structure." This is true. Sulphur plays a crucial role in the stabilization of protein structures, particularly in the formation of disulfide bonds between cysteine residues in proteins.

2. **Understanding the Reason (R)**:
- The reason given is that "It does not participate in metabolic processes." This statement is false. While it is true that sulfur's primary role in proteins is structural, it is also involved in metabolic processes in certain organisms.

3. **Role of Sulphur in Protein Structure**:
- Sulphur is found in the amino acid cysteine, which can form disulfide bonds (–S–S–) that help stabilize the tertiary structure of proteins. These bonds are important for maintaining the three-dimensional shape of proteins, which is essential for their function.

4. **Metabolic Processes Involving Sulphur**:
- Certain bacteria, known as sulfur bacteria, can utilize sulfur in their metabolic processes. These bacteria can use sulfur compounds in the absence of oxygen to produce energy, demonstrating that sulfur does participate in metabolic reactions in specific contexts.

5. **Conclusion**:
- Therefore, the assertion (A) is true, while the reason (R) is false. The correct relationship is that while sulfur stabilizes protein structure, it is not accurate to say it does not participate in metabolic processes, as it does in certain organisms.

**Final Answer**: Assertion (A) is true and Reason (R) is false.

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