Galactose is a monosaccharide composed of six carbons and one aldehyde group. It is an aldohexose and a C-4 epimer of glucose. Galactose is a component of lactose in mammalian milk. It often exists in the brain and Nervous tissue in the form of D-galactoside, and is also an important component of some glycoproteins. Galactose is the fastest monosaccharide absorbed in the intestine.