Question

Identify the correct statements. (Note: Based on options, the question asks to identify INCORRECT statements).
A. Arginine and Tryptophan are essential amino acids.
B. Glycine does not have chiral centre.
C. Proline is a six membered cyclic ring amino acid.
D. Histidine does not contain heterocyclic ring in its structure.
E. Cysteine has characteristic feature of side chain as \(MeS-CH_2-CH_2-\).

• A. B and E Only
• B. A and D Only
• C. C and D Only
• D. C and E Only

Hint:

Remember the unique features: Proline (2-degree amine, 5-membered ring), Histidine (Basic, Imidazole ring), Cysteine (Thiol -SH), Methionine (Thioether -S-Me).

Answer 1

The Correct Option is D

Step 1: Analysis of Each Statement

A: Arginine and tryptophan are classified as essential amino acids. (Arginine is conditionally essential, especially for growing children.) (True)

B: Glycine (\(NH_2–CH_2–COOH\)) has two hydrogen atoms attached to the α-carbon, hence it does not have a chiral centre and is achiral. (True)

C: Proline contains a pyrrolidine ring, which is a five-membered nitrogen-containing ring. Hence the statement is correct. (True)

D: Histidine contains an imidazole ring, which is a heterocyclic aromatic ring. Hence the statement is correct. (True)

E: The side chain \(CH_3–S–CH_2–CH_2–\) belongs to methionine, whereas cysteine has the side chain \(HS–CH_2–\). Hence the statement is incorrect. (False)

Step 2: Identification of Incorrect Statements

From the above analysis:
• Statements A, B, C, and D are correct.
• Statement E is incorrect.

Therefore, the only incorrect statement is E.

Final Answer:
The incorrect statement is E.