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

Question

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

Accepted Answer

Correct answer: C. (c) HN_3-CH_2- COO^- Glycine ( Gly ) HOOC-CH_2- CH- COO^- |+NH_3 Aspartic acid ( Asp ) H_2N- (CH_2 )_4- CH- COO^- |+NH_3 Lysine ( Lys ) NH | |H_2N-C- NH- (CH_2 )_3- CH- COO^- |+NH_3 Arginine ( Arg ) Here, aspartic acid is an acidic and glycine is a neutral amino acid while lysine and arginine are basic amino acids. Also, arginine is more basic due to be the stronger basic functional groups. ∴ The order of pKa value is directly proportional to the basic strength of amino acids, i.e., Arg> Lys >Gly> Asp.

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

Solution

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