Question

The CORRECT statement(s) regarding biomolecules is(are):

• A. The N-terminal amino acid of a polypeptide can be identified by Edman’s reagent (phenyl isothiocyanate).
• B. L-Threonine has only one chiral center.
• C. Cytosine is present both in RNA and DNA.
• D. A mixture of different amino acids can be separated by ion-exchange chromatography.

Hint:

Ion-exchange chromatography is a versatile technique that separates molecules based on their charge. In the case of amino acids, their separation depends on their differing pH and charge properties.

Answer 1

The Correct Option is A, C, D

Let's analyze the statements one by one:

- (A): Edman’s reagent, which is phenyl isothiocyanate, is used to identify the N-terminal amino acid in a polypeptide chain. This reagent reacts with the free amino group of the N-terminal residue to form a phenylthiohydantoin derivative, which can be identified and sequenced. This process is useful for determining the sequence of a polypeptide, so statement (A) is correct.

- (B): L-Threonine actually has two chiral centers, not just one. One is at the carbon attached to the hydroxyl group (-OH), and the other is at the central carbon (which is attached to the amino group, the carboxyl group, and the side chain). Therefore, statement (B) is incorrect.

- (C): Cytosine is a nitrogenous base that is found in both RNA and DNA. It pairs with guanine in both types of nucleic acids. Hence, statement (C) is correct.

- (D): Ion-exchange chromatography is a powerful method used to separate amino acids based on their net charge. In this technique, amino acids are separated by passing them through a column that contains charged groups. The amino acids will interact differently with the column based on their charge, making this statement correct.

Thus, the correct answers are (A), (C), and (D).