The increasing order of pKa of the following amino acids in aqueous solution is :
Gly Asp Lys Arg

see full answer

Your Exam Success, Personally Taken Care Of

1:1 expert mentors customize learning to your strength and weaknesses – so you score higher in school , IIT JEE and NEET entrance exams.

An Intiative by Sri Chaitanya

$Gly < Asp < Arg < Lys$

$Asp < Gly < Lys < Arg$

$Arg < Lys < Gly < Asp$

$Asp < Gly < Arg < Lys$

answer is D.

(Unlock A.I Detailed Solution for FREE)

JEE

NEET

Foundation JEE

Foundation NEET

CBSE

Detailed Solution

The increasing order of pKa (i.e., from most acidic to most basic conjugate acid) among the given amino acids in aqueous solution is:

Asp < Gly < Lys < Arg

Reasoning:

Aspartic acid (Asp) has an extra carboxyl side chain, making it the most acidic and thus lowest pKa.
Glycine (Gly) is neutral with no additional ionizable side chain, so it has higher pKa than Asp.
Lysine (Lys) has an ε-amino side chain that is basic, giving it higher pKa than Gly.
Arginine (Arg) has a guanidinium side chain, which is even more basic than lysine’s amino group, thus the highest pKa.

Therefore: Asp < Gly < Lys < Arg.

Watch 3-min video & get full concept clarity