Chapter 16.2, Problem 16.11QAP

Interpretation Introduction

Interpretation: The overall charge of a nonpolar amino acid at a pH below its pI.

Concept introduction:

➢ Amino acid: Any molecule contains both amino and acid group

Ex:

➢ The $$ group can be simple as hydrogen atom (glycine) to more complicated groups such as alcohols, amines and aromatic.

➢ If $\text{R}$ is non polar

Then it is called non polar amino acid.

Ex:

The amino acid has two group,

➢ One acts as base and other acts as acid. So net charge or from of amino acid depends upon $\text{pH}$ value as follows:

➢ Amino acid is any molecule that contains both amino and acid group. If $\text{pH = pI}$ then net charge on amino acid is zero called zwitterion from contains equal no of$\text{+ve and }-\text{ve}$ charge.

➢ If $\text{pH > pI}$, then at this ${\text{pH H}}_3{\text{N}}^{+}-$ acts as acid and donates one proton $\left({\text{H}}^{+}\right)$ to for ${\text{H}}_2\text{N}-$

And it has total charge $=1-$

➢ If $\text{pH < pI}$, then

Acts as base and accept one proton $\left({\text{H}}^{+}\right)$ form solution and convert to

So at such $\text{pH}$ it has total charge $=1+$