BSA makes up approximately 60% of all proteins in animal serum. It is commonly used in cell culture protocols, particularly when protein supplementation is necessary and the other components of serum are unwanted. It aids in stabilization of enzymes and other proteins to prevent proteolysis and denaturation, especially when the proteins are present in low concentrations. In cell culture its main role is as a carrier of small molecules. Because of its negative charge, BSA binds water, salts, fatty acids, vitamins and hormones, then carries these bound components between tissues and cells. The binding capacity also makes BSA an effective scavenger for removing toxic substances, including pyrogens, from the medium.