The side chain of which of the following amino acids contains -NH2 gr…

The correct answer is Option (4) → A and C only

All α-amino acids have the general formula \( \ce{R-CH(NH2)-COOH} \). The α-\( \ce{NH2} \) and –COOH groups are common to all of them; the amino acids differ only in the side chain R. The question asks whether that side chain itself carries an –\( \ce{NH2} \) group (free or as part of a larger group such as an amide or guanidino group).

• A. Arginine — Correct. R = \( \ce{HN=C(NH2)-NH-(CH2)3} \)–; the guanidino group at the end contains –\( \ce{NH2} \). It is a basic amino acid.

• B. Threonine — Incorrect. R = \( \ce{CH3-CH(OH)} \)–; the side chain carries an –OH group, not –\( \ce{NH2} \).

• C. Asparagine — Correct. R = \( \ce{H2N-CO-CH2} \)–; the amide group –\( \ce{CONH2} \) contains –\( \ce{NH2} \).

• D. Tyrosine — Incorrect. R = \( \ce{HO-C6H4-CH2} \)–; the side chain carries a phenolic –OH group.

NCERT (2026-27 edition):
Amino Acids

* essential amino acid