Amino acids are the building blocks of proteins. They band together in chains to form the stuff from which your life is born. Think of amino acids as Legos for your life.It's a two-step process: Amino acids get together and form peptides or polypeptides. It is from these groupings that proteins are made. And there's not just one kind of amino acid. A total of 20 different kinds of amino acids form proteins. The kinds of amino acids determine the shape of the proteins formed. Commonly recognized amino acids include glutamine, glycine, phenylalanine, tryptophan, and valine. Three of those - phenylalanine, tryptophan, and valine - are essential amino acids for humans; the others are isoleucine, leucine, lysine, methionine, and threonine. The essential amino acids cannot be synthesized by the body; instead, they must be ingested through food.