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Lactose (also referred to as milk sugar) is a sugar which is found most notably in milk. Lactose makes up around 2–8% of the solids in milk. The name comes from the Latin word for milk, plus the -ose ending used to name sugars.
Additional recommended knowledge
Lactose has a solubility of 1 in 4.63 measured %w/v. This translates to 0.216g of lactose dissolving readily in 1mL of water.
Digestion of lactose
Infant mammals are fed on milk by their mothers. To digest it an enzyme called lactase (β-D-galactosidase) is secreted by the intestinal villi, and this enzyme cleaves the molecule into its two subunits glucose and galactose for absorption.
Since lactose occurs mostly in milk, in most mammals the production of lactase gradually decreases with maturity. However, production never ceases completely; it is controlled by the presence of lactose in the diet, which in turn deactivates the repressor of the lac operon, allowing lactase to be synthesized. In other words, lactose induces the synthesis of the enzyme which breaks it down. (See also: gene expression.)
Many people with ancestry in Europe, the Middle East, India, or parts of East Africa, maintain normal lactase production into adulthood. In many of these cultures mammals such as cattle, goats, and sheep are milked for food. Hence, it was in these regions that genes for lifelong lactase production first evolved.
|This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Lactose". A list of authors is available in Wikipedia.|