Statement I: Except glycine, all other naturally occurring α-amino acids are optically active, since their α-carbon atom is asymmetric.
Statement II: L-Amino acids are represented by writing the –NH2 group on the left hand side.
In the light of the above statements, choose the correct answer from the options given below:
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → Both Statement I and Statement II are correct.
In an α-amino acid, R–CH(NH2)–COOH, the α-carbon carries four groups: –H, –NH2, –COOH and the side chain R. When all four are different, the carbon is asymmetric and the amino acid exists in D and L forms.
Statement I: Except glycine, all other naturally occurring α-amino acids are optically active, since their α-carbon atom is asymmetric. — True. In glycine the side chain R is H, so the α-carbon carries two hydrogen atoms and is not asymmetric; every other natural α-amino acid has an asymmetric α-carbon.
Statement II: L-Amino acids are represented by writing the –NH2 group on the left hand side. — True. With –COOH at the top, the –NH2 group on the left shows the L-form; most naturally occurring amino acids have this L-configuration.
NCERT (2026-27 edition):
10.2.2 Classification of Amino Acids – “Except glycine, all other naturally occurring α-amino acids are optically active, since the α-carbon atom is asymmetric. These exist both in ‘D’ and ‘L’ forms. Most naturally occurring amino acids have L-configuration. L-Aminoacids are represented by writing the –NH2 group on left hand side.”