glossary

lactose

Definition lactose

lactose

lactose n. a sugar, consisting of one molecule of glucose and one of galactose, found only in milk. Lactose is split into its constituent sugars by the enzyme *lactase, which is secreted in the small intestine. This enzyme is missing or is of low activity in certain people of some Eastern and African races. This leads to the inability to absorb lactose, known as lactose intolerance.