Match List-I with List-II
|
List-I Amino acid |
List-II R group |
|
(A). Alanine |
(I). \( -CH_3 \) |
|
(B). Lysine |
(II). \( HO-CH_2- \) |
|
(C). Serine |
(III). \( H_2N-(CH_2)_4- \) |
|
(D). Cysteine |
(IV). \( HS-CH_2- \) |
Choose the correct answer from the options given below:
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → (A)-(I), (B)-(III), (C)-(II), (D)-(IV)
Every α-amino acid has the general formula \( \ce{H2N-CH(R)-COOH} \): an amino group and a carboxyl group on the same carbon, with a side chain R that differs from one amino acid to another. The R group decides whether the amino acid is neutral, acidic or basic.
(A). Alanine — This matches (I). \( \ce{-CH3} \). Alanine is \( \ce{CH3-CH(NH2)-COOH} \), the simplest amino acid after glycine, with a methyl side chain.
(B). Lysine — This matches (III). \( \ce{H2N-(CH2)4-} \). Lysine has a second amino group at the end of a four-carbon chain, which makes it a basic amino acid.
(C). Serine — This matches (II). \( \ce{HO-CH2-} \). Serine carries a hydroxymethyl side chain.
(D). Cysteine — This matches (IV). \( \ce{HS-CH2-} \). Cysteine carries a thiol (–SH) group; two cysteine units can join through a disulphide (–S–S–) bond.
Shortcut: (B)-(III), lysine with the extra amino group, appears only in Option (2).
NCERT (2026-27 edition):
Amino Acids
Table 10.2: Natural Amino Acids (rows)
| Name of the amino acid | Characteristic feature of side chain, R |
|---|---|
| 2. Alanine | –CH3 |
| 7. Lysine* | H2N–(CH2)4– |
| 13. Serine | HO–CH2– |
| 14. Cysteine | HS–CH2– |