Bile is a yellowish-green fluid produced by liver cells and stored in the gall bladder. It is released into the duodenum after a meal. The main components of bile are water, bile acids (see below), bile pigments, and cholesterol. Cholesterol and bile pigments from the breakdown of hemoglobin are excreted from the body in the bile.
Bile acids are a group of steroid acids present in bile. In humans, the commonest is cholic acid (C24H40O5), which is conjugated by its carboxyl group to the amino groups of the amino acids glycine and taurine. Bile acids act as emulsifying agents in the digestion and absorption of fats, and also aid digestion of vitamins A, D, E, and K., thus promoting their absorption by the small intestine.