Albumin

A class of water-soluble PROTEINS that are soluble in dilute salt solutions but are insoluble in pure water. Important members of this class are serum albumin and ovalbumin. The LIVER produces serum albumin, the most plentiful protein in serum. Serum albumin transports ions like CALCIUM, free FATTY ACIDS, and fat-soluble materials like BILIRUBIN through the blood. Serum albumin also helps buffer the blood. It is a highly charged molecule (polyelectrolyte) that cannot pass through cell membranes and thus helps maintain the electrolyte balance of body fluids. Ovalbumin is one of the most abundant proteins of egg white. The Roman author Pliny recorded the name of egg white as albumen. Ovalbumin is an excellent source of sulfur-containing amino acids, such as CYSTEINE, and this accounts in part for the excellent food value of egg protein.