JEE Main · 2019 · 09 Jan 2019 · Shift 1 · Biomolecules

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

(A)Asp < Gly < Arg < Lys
(B)Gly < Asp < Arg < Lys
(C)Asp < Gly < Lys < Arg✓ Correct
(D)Arg < Lys < Gly < Asp

Answer: (C)

Solution

Rank these by how acidic their characteristic groups are, remembering that a lower

p K_{a}

means more acidic. Aspartate carries an extra

- COOH

and is the most acidic with the lowest

p K_{a}

, glycine is neutral and sits next, while lysine with its extra

- NH X_{2}

and arginine with its guanidinium group are basic and carry high

p K_{a}

values, arginine the highest of all. The increasing order is Asp

<

Gly

<

Lys

<

Arg.

JEE Main · 2019 · 09 Jan 2019 · Shift 1 · Single correct option

Practise more: all JEE Main PYQs on Biomolecules →

More JEE Main questions on Biomolecules

Identify the correct statements.

A. Arginine and Tryptophan are essential amino acids.
B. Histidine does not contain heterocyclic ring in its structure.
C. Proline is a six membered cyclic ring amino acid.
D. Glycine does not have chiral centre.
E. Cysteine has characteristic fe …
JEE Main 2026View solution →
Given below are two statements:

Statement I: Sucrose is dextrorotatory. However sucrose upon hydrolysis gives a solution having mixture of products. This solution shows laevorotation.

Statement II : Hydrolysis of sucrose gives glucose and fructose. Since the laevorotation of gl …
JEE Main 2026View solution →
The correct statements are:
A. Activation energy for enzyme catalysed hydrolysis of sucrose is lower than that of acid catalysed hydrolysis.
B. During denaturation, secondary and tertiary structures of a protein are destroyed but primary structure remains intact.
C. Nucleotides a …
JEE Main 2026View solution →
Match List-I with List-II.

List-I
Reaction of glucose with
A. Hydroxylamine
B. $Br_{2}$ water
C. Excess acetic anhydride
D. Concentrated $HNO_{3}$

List-II
Product formed
I. Glouconic acid
II. Glucose pentacetate
III. Saccharic acid
IV. Glucoxime

Choose th …
JEE Main 2026View solution →
Both human DNA and RNA are chiral molecules. The chirality in DNA and RNA arises due to the presence of
JEE Main 2026View solution →
The number of possible tripeptides formed involving alanine (ala), glycine (gly) and valine (val), where no amino acid has been used more than once is :
JEE Main 2026View solution →