Glycine is a protein amino acid found in the protein of all life forms. It is the simplest amino acid in the body and the only protein amino acid that does not have chirality. Although most glycine is found in proteins, free glycine is found in body fluids as well as in plants. Glycine is not considered an essential amino acid, i. e., the cells in the body can synthesize sufficient amounts of glycine to meet physiological requirements. However, glycine is of major importance in the synthesis of proteins, peptides, purines, adenosine triphosphate (ATP), nucleic acids, porphyrins, hemoglobin, glutathione, creatine, bile salts, one-carbon fragments, glucose, glycogen, and L-serine and other amino acids. Glycine is also a neurotransmitter in the central nervous system.