Amino acids are compounds that have amine (NH2) and carboxyl (COOH) groups and a side chain that is unique to a specific amino acid.

Amino acids are the building blocks of proteins that are linked together by the peptide bond. A peptide bond is a bond between two molecules where the carboxyl (COOH) group of one molecule reacts with the amino (NH2) group of another molecule. The side chain difference is what defines the exclusive properties of each amino acid.

There are hundreds of amino acids that exist in nature, but only 20 of them are needed to sustain the forms of life. The human body, just like any other life form, needs these 20 amino acids for growth and proper functioning. However, only 9 of them are considered essential – leucine, valine, tryptophan, threonine, methionine, isoleucine, lysine, histidine, and phenylalanine. Essential amino acids are those that can’t be synthesized by a human body. Non-essential amino acids are those the human body can synthesize. They can be excluded from our diet, and we will be more than capable of synthesizing them on our own. However, we need to obtain essential amino acids through food. It is interesting how some non-essential amino acids may be considered conditionally essential because our body cannot synthesize the needed amount during some periods of our lives, such as puberty, pregnancy, illness, or even stress.