Amino Acids

An amino acid is a type of organic acid that contains a carboxyl functional group (-COOH) and an amine functional group (-NH2) as well as a side chain (designated as R) that is specific to the individual amino acid.
Amino acids are considered to be the building blocks of polypeptides and proteins.
The elements found in all amino acids are carbon, hydrogen, oxygen, and nitrogen. Amino acids may contain other elements on their side chains.
Because they are used to build proteins, most of the human body consists of amino acids.
Amino acids are used to build a variety of molecules and are used in neurotransmitter and lipid transport.


Amino acids are classified into three groups:

  • Essential amino acids
  • Nonessential amino acids
  • Conditional amino acids

Essential Amino Acids

Essential amino acids cannot be made by the body. As a result, they must come from food. The 9 essential amino acids are: histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, and valine.

Nonessential Amino Acids

Nonessential means that our bodies produce an amino acid, even if we do not get it from the food we eat. Nonessential amino acids include: alanine, asparagine, aspartic acid, and glutamic acid.

Conditional Amino Acids

Conditional amino acids are usually not essential, except in times of illness and stress. Conditional amino acids include: arginine, cysteine, glutamine, tyrosine, glycine, ornithine, proline, and serine.

Conditional amino acids