Most of the creatine in the body is stored in the muscles as creatine or in a form called phosphocreatine.
Creatine is a quickly available energy source for muscle contraction.
There are twenty amino acids needed to build the various proteins used in the growth, repair, and maintenance of body tissues. The classification of an amino acid as essential or nonessential does not reflect its importance, because all twenty amino acids are necessary for health. Instead, this classification system simply reflects whether or not the body is capable of manufacturing a particular amino acid.