Galactose is a simple monosaccharide sugar naturally occurring in milk. When it’s chemically linked with glucose, it forms lactose, the principal sugar in milk and dairy foods. Galactose is important in early human development and plays a key role in our metabolism, even as adults. Galactose ist eine Hexose und hat wie alle Hexosen die Summenformel C 6 H 12 O 6. Sie ist stereoisomer (genauer gesagt ein C4- Epimer) zur Glucose und gehört zur Untergruppe der Aldohexosen. Galactose (C6 H 12 O 6) is an important carbohydrate for cellular metabolism and one of the most abundant sugars in the human diet [37]. It is a reducing monosaccharide containing six carbon atoms, similar to glucose. Galactose is a naturally occurring monosaccharide that forms the disaccharide lactose when combined with glucose (another monosaccharide). Galactose, a member of a group of carbohydrates known as simple sugars (monosaccharides). It is usually found in nature combined with other sugars, as, for example, in lactose (milk sugar). Galactose is also found in complex carbohydrates (see polysaccharide) and in carbohydrate-containing lipids. Galactose, like glucose, is an ubiquitous aldohexose, which also exists as a d -isomer in nature. It is found in most living cells, including yeasts and bacteria. Galactose exists in both open-chain and cyclic form. The open-chain form is an aldehyde (RCHO). Four isomers are cyclic, two of them with a pyranose (six-membered) ring and two with a furanose (five-membered) ring. Galactose is a simple sugar, which belongs to simple carbohydrates. Galactose is composed of the same elements as glucose, but has a different arrangement of atoms. Galactose is classified as a monosaccharide, an aldose, a hexose, and is a reducing sugar. One baby out of every 18,000 is born with a genetic defect of not being able to utilize galactose. Since galactose is in milk as part of lactose, it will build up in the blood and urine. Galactose is a fundamental simple sugar, chemically known as a monosaccharide. It is one of the three main dietary monosaccharides, alongside glucose and fructose, that the body absorbs directly for energy.