Question

Give the general formula for an amino acid. Some amino acids are labelled hydrophilic and some are labelled hydrophobic. What do these terms refer to?

Short answer

Hydrophilic side groups are oriented towards the water hydrophobic side groups are oriented towards each other avoiding exposure to the solution.

Step-by-step solution

General amino acid

The general formula of amino acid is shown in the picture below, where all parts are marked with a different color. There are three parts in the amino acid.

The first one is a carboxyl group marked with red color. The second one is an amino group marked with blue color. These two groups are present in every amino acid.

To give the general formula for an amino acid

The last part of amino acid is side group R marked with green color. This part is different for every type of amino acid. Hydrophobic side groups contain non-polar groups. Hydrophilic groups are polar and they contain groups such as -OH,$\text{COOH and NH2}$.

The difference between these two terms is in orientation in the water solution. While hydrophilic side groups are oriented towards the water, hydrophobic side groups are orientated towards each other avoiding exposure to the solution.

General form of amino acids

Hence Hydrophilic side groups are oriented towards the water hydrophobic side groups are oriented towards each other avoiding exposure to the solution.