Chapter 2, Problem 10P

Interpretation Introduction

Interpretation:

The pH value at which a solution of the given amino acid would have no net charge should be indicated.

Concept introduction:

The ionization of an amino acid depends on the pH. In acidic pH both amino group and carboxylate group are protonated. When pH increases, the carboxylic acid is the first to deprotonate. At higher pH’s the protonated form of amino group also lose a proton.

The isoelectric point is the pH at which, a molecule does not have any net charge. And pI can be calculated using following formula

$\text{pI = }\frac{{\text{pK}}_{a1}+{\text{ pK}}_{a2}}{2}$.

pI − isoelectric point.

K_a1 and K_a2 − dissociation constant of alpha amino group and alpha carboxylic group.