Amino acids are the building blocks of proteins. Our bodies need amino acids in order to make new cells and enzymes. Out of the 20 types of amino acids that exist, we can make 10. The other 10 must come from our diet.
An amino acid has an amino group (NH2) and a carboxyl group (COOH), and a side chain (R group) that makes one amino acid type different from another.
A chain of amino acids is called a polypeptide. To link up amino acids, an amino group from one amino acid reacts with a carboxyl group of another amino acid, and they are joined by removal of a water molecule (called a dehydration reaction) to form a peptide bond. Amino acids can be further added to the sides of the chain to form a long polypeptide.