Question

How can you tell if an amino side chain is polar or nonpolar? Give an example of each

Answer 1

Amino acids are building blocks of the proteins, they are required for the formation of protein primary structure.

An amino acid can be either polar or nonpolar.

Among the 20 amino acids that we have, 11 are polar and rest of the 9 are non polar.

We can decide whether the amino acid is polar or not by its polarity.

An amino acid is said to be nonpolar if it has side chains of pure hydrocarbon alkyl groups or aromatic groups .

We can predict this by the presence of alkyl groups ,the more the number of alkyl groups the more the non polar is the amino acid.

This is the reason why leucine is more non polar than valine

Some of the examples of non polar amino acids are valine, leucine, alanine , phenylalanine etc.

Whereas an amino acid is said to be polar , when the side chains have various functional groups .

Some of the functional groups are amides, acids, alcohols, amines.

Moreover the polarity order also depends on the order of the functional groups only.

More the polar nature of the functional group ,more polar is the amino acid.

Example aspartic acid is more polar than serine, because serine has hydroxyl group and aspartic acid has acid group, as acid group is more polar ,aspartic acid is more polar.

Some of the examples of polar amino acids are lysine, serine, glutamine, aspartic acid , glutamic acid etc.

Finally we can say that if the amino acid have side chains attached to alkyl or aromatic groups it is non polar.

If it has functional group attached to it is polar.

Likewise the amino acids can be also be differentiated as acidic, basic or neutral .