Proteins are the fundamental components of all living cells and include a diverse range of biological substances, such as enzymes, hormones, and antibodies, that are necessary for the proper functioning of any organism, plant or animal. The human body contains perhaps 100,000 different proteins, each composed of an assortment of 20 or so amino acids. The sequence of these amino acids determines the unique properties of each protein, such as, for example, its role as an enzyme acting as a catalyst for a specific biochemical reaction. If even one of the essential amino acids is missing, the protein cannot be formed. This fact is well known to nutritionists because ensuring an adequate supply of essential amino acids is important in determining the nutritional value of proteins in the diet. Components of proteins can have varying benefits for skin, but overall they are used for their water-binding and emollient properties.