The term "essential" refers to a specific nutrient that the body is not capable of producing, but does not require.If the essential nutrient is not supplied through diet or supplementation, a deficiency for that particular nutrient may occur.
As with protein synthesis, if one amino acid is supplied in a smaller amount than necessary (i.e., incomplete proteins or low-quality protein), then, the total amount of protein that can be synthesized from other amino acids will be limited. When this occurs, body protein-synthesis is restricted. If one essential amino acid is completely absent, however, the other amino acids can not be utilized and are therefore, wasted by the body.
Daryl Conant. M.Ed