Galactose
Galactose is a type of sugar found in milk products and sugar beets. It is also made by the body. It is considered a nutritive sweetener because it has calories.
Galactose is a monosaccharide constituent, together with glucose, of the disaccharide lactose. The hydrolysis of lactose to glucose and galactose is catalyzed by the enzyme beta-galactosidase, a lactase.
Individuals who lack this enzyme are 'lactose_intolerant' and unable to realize the nutritive potential of milk sugars. The lactose then passes to the large intestine where it is digested by bacteria, producing gas and flatulence.
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Structure
The first and last -OH groups point the same way and the second and third -OH groups point the other way.
Isomerism
D-Galactose has the same configuration at its penultimate carbon as D-glyceraldehyde.
Reactions
Galactose is hydrolysed by lactase.
