JEE Main Chemistry Class 12 Biomolecules Part 1 Questions

Structure of the given α -amino acids are:

H3N−CH2−COO−

Glycine(Gly)

HOOC−CH2− C ↲ NH3 H−COO−

Aspartic‌acid(Asp)

H2N−(CH2)4− C ↲ NH3 H−COO−

Lysine(Lys)

H2N− NH || C −NH−(CH2)3− C ↲ NH3 H−COO−

Arginine(Arg)

Here, aspartic acid is acidic, glycine is neutral, while lysine and arginine are basic amino acids. Also, arginine is more basic due to stronger basic functional groups. ∴ The order of pKa value is directly proportional to the basic strength of amino acids, thus Arg> Lys > Gly > Asp.