Question

Among the following, the structure representing histidine is:

• A.
• B.
• C.
• D.

Hint:

Histidine's imidazole ring plays a crucial role in enzyme active sites due to its ability to donate and accept protons, making it essential in biological catalysis.

Answer 1

The Correct Option is C

Step 1: Understanding the structure of histidine.

Histidine is an essential amino acid with an imidazole side chain, making it one of the basic amino acids. It consists of:

• An amino group (\( \text{NH}_3^+ \)) at physiological pH,
• A carboxyl group (\( \text{COO}^- \)),
• An imidazole ring as the side chain.

Step 2: Analyzing the options.

• Option (A) lacks the imidazole side chain.
• Option (B) represents an incorrect ring structure (pyrrole).
• Option (C) correctly depicts the imidazole ring along with the amino and carboxyl groups, characteristic of histidine.
• Option (D) does not include the imidazole ring, which is essential for histidine.

Conclusion.

The structure in option (C) accurately represents histidine with its imidazole side chain, amino group, and carboxyl group.