Galactose

Galactose is a six-carbon monosaccharide found in organisms and foods. It commonly occurs bonded to glucose in lactose and is also a component of cell-surface molecules.

Monosaccharide: A simple carbohydrate consisting of one sugar unit that cannot be hydrolyzed into smaller carbohydrates. Galactose is one sugar unit, the basic structural category of monosaccharides.
Leloir pathway: The principal pathway that converts galactose into glucose-1-phosphate through nucleotide-sugar intermediates. This pathway processes dietary and cellular galactose for use in metabolism.
Lactose: A disaccharide made of glucose and galactose, naturally abundant in milk. Digestion of lactose releases galactose alongside glucose.
Glycan: A molecule or molecular region composed of linked sugar units. Galactose is a building block in many larger carbohydrate structures.
Aldose: A monosaccharide containing an aldehyde group in its open-chain form. Galactose belongs to the aldose family because its open-chain form has an aldehyde group.
Galactokinase: An enzyme that phosphorylates galactose to produce galactose-1-phosphate. It catalyzes the first step of the Leloir pathway.
Lactase: An enzyme that hydrolyzes lactose into glucose and galactose. Lactase determines how efficiently lactose supplies galactose during digestion.
Glycosidic bond: A covalent bond that joins a sugar’s anomeric carbon to another group or molecule. This bond links galactose to glucose in lactose and to other sugars in glycans.
Hexose: A monosaccharide containing six carbon atoms. Its six-carbon backbone makes galactose a hexose.
Galactose-1-phosphate uridylyltransferase: An enzyme that transfers a uridylyl group between galactose-1-phosphate and UDP-glucose. This enzyme exchanges galactose-derived and glucose-derived sugar groups in the pathway.

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