Nonessential amino acids are amino acids made by the body from essential amino acids or normal breakdown of proteins. Of the 20 standard amino acids, 12 are nonessential. These are: alanine, asparagine, aspartate, cysteine, glutamate, glutamine, glycine, proline, serine, tyrosine, arginine, and histidine. The amino acids cysteine, tyrosine, histidine and arginine are considered semiessential amino acids in children, because the metabolic pathways that synthesize these amino acids are not fully developed yet.