Dictionary:

lactose

  (lăk'tōs')

1. A disaccharide, C₁₂H₂₂O₁₁, found in milk, that may be hydrolyzed to yield glucose and galactose.
2. A white crystalline substance obtained from whey and used in infant foods, bakery products, confections, and pharmaceuticals as a diluent and excipient. Also called milk sugar.

Milk sugar or 4-O-β-D-galactopyranosyl-D-glucose. This reducing disaccharide is obtained as the α-D anomer (see formula, where the asterisk indicates a reducing group); the melting point is 202°C (396°F). Lactose is found in the milk of

The carbohydrate of milk, sometimes called milk sugar. A disaccharide of glucose and galactose. Used pharmaceutically as a tablet filler and as a medium for growth of micro-organisms. The fermentation of lactose to lactic acid by bacteria is responsible for the souring of milk. Ordinary lactose is α-lactose, which is 16% as sweet as sucrose; if crystallized above 93 °C, it is converted to the β-form which is more soluble and sweeter.

A sugar found in milk. It is a disaccharide made by the combination of galactose and glucose. Milk goes sour because the lactose is converted by bacteria into lactic acid. Lactose is an energy-rich food but some people suffer from lactose intolerance in which the consumption of milk (or other foods containing lactose) causes cramps, flatulence, and diarrhoea.

Lactose intolerance is due to a deficiency in the production of lactase, an enzyme that digests lactose into glucose and galactose. It most often affects people who consume few milk products, but since lactase production tends to reduce with age, a large proportion of the population may suffer some degree of lactose intolerance as they grow older. In fact, most ethnic groups (apart from Caucasians) do not retain lactase past adolescence so most adults are lactose intolerant. A few sufferers can still eat some fermented dairy products, such as buttermilk and yoghurt, or they may be able to obtain lactase-treated products. Others may have to avoid dairy products altogether. These people have to find alternative sources of the nutrients, such as calcium and riboflavin, that they would otherwise obtain from milk or its products.

[LAK-tohs] This sugar occurs naturally in milk and is also called milk sugar. It's the least sweet of all the natural sugars and is used commercially in foods such as baby formulas and candies.

A disaccharide found in the milk of all mammals. Lactose is used as a component of formulas for infants; it is also used as a laxative and a diuretic.

For more information on lactose, visit Britannica.com.

A disaccharide sugar made from galactose and glucose; milk sugar. Although lactose is potentially a rich source of energy, many people suffer from lactose intolerance because they lack the enzyme (lactase) required to digest it.

A sugar derived from milk, which on hydrolysis yields glucose and galactose.

• l. digestion test — oral test of foal's ability to digest milk sugar.
• l. intolerance — inability to digest lactose in the diet because of the lack of the enzyme lactase in the small intestine. Clinical consequences are intestinal discomfort and diarrhea.
• l. tolerance test — a monitor of intestinal epithelial damage, similar to the starch digestion test. The test measures the rise in blood glucose at timed intervals after oral administration of lactose; essentially a test of disaccharidase efficiency of the gut.

Lactose
Identifiers
CAS number	63-42-3
PubChem	6134
MeSH	Lactose
Properties
Molecular formula	C12H22O11
Molar mass	342.296
Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa) Infobox disclaimer and references

Lactose is a disaccharide that consists of β-D-galactose and β-D-glucose molecules bonded through a β1-4 glycosidic linkage. 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.

Digestion of lactose

Main article: Lactose intolerance

Infant mammals are fed on milk by their mothers. To digest it an enzyme called lactase (β1-4 disaccharidase) 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 species the production of lactase gradually ceases with maturity, and they are then unable to metabolise lactose. This loss of lactase on maturation is also the default pattern in most adult humans.[1] However, many people with ancestry in Europe, the Middle East, India, or parts of East Africa, maintain lactase production into adulthood. In many of these cultures other mammals such as cattle, goats, and sheep are milked for food.

This fact may cast doubt on some arguments by proponents of the Paleolithic diet,^{[citation needed]} who argue that human metabolic needs have not changed since the last ice age. The process of retaining infant characteristics into adulthood is one of the simplest routes of adaptation, and is known as neoteny.

Solubility

8 g lactose per 10 g [2]

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.

The solubility of lactose in water is 18.9049 g at 25 °C, 25.1484 g at 40 °C and 37.2149 g at 60 °C per 100 g solution. Its solubility in ethanol is 0.0111 g at 40 °C and 0.0270 g at 60 °C per 100 g solution. [3]

See Also

Lac Operon

External links

• Study Detects Recent Instance of Human Evolution (Finding that lactose tolerance is a recent change)

• Lactose Intolerence (click on the link for more information)

Major families of biochemicals
Peptides | Amino acids | Nucleic acids | Carbohydrates | Lipids | Terpenes | Carotenoids | Tetrapyrroles | Enzyme cofactors | Steroids | Flavonoids | Alkaloids | Polyketides | Glycosides
Analogues of nucleic acids:	Types of Carbohydrates	Analogues of nucleic acids:
General:	Aldose | Ketose | Pyranose | Furanose
Geometry:	Triose | Tetrose | Pentose | Hexose | Heptose | Cyclohexane conformation | Anomer | Mutarotation
Small/Large:	Glyceraldehyde | Dihydroxyacetone | Erythrose | Threose | Erythrulose | Sedoheptulose
Trioses:	ketotriose | Aldotriose
Tetroses:	Erythrulose | Erythrose | Threose
Pentoses:	Arabinose | Deoxyribose | Lyxose | Ribose | Ribulose | Xylose | Xylulose
Hexoses:	Glucose | Galactose | Mannose | Gulose | Idose | Talose | Allose | Altrose | Fructose | Sorbose | Tagatose | Psicose | Fucose | Rhamnose
Disaccharides:	Sucrose | Lactose | Trehalose | Maltose
Polymers:	Glycogen | Starch (Amylose | Amylopectin) | Cellulose | Chitin | Stachyose | Inulin | Dextrin
Glycosaminoglycans:	Heparin | Chondroitin sulfate | Hyaluronan | Heparan sulfate | Dermatan sulfate | Keratan sulfate
Aminoglycosides:	Kanamycin | Streptomycin | Tobramycin | Neomycin | Paromomycin | Apramycin | Gentamicin | Netilmicin | Amikacin

This entry is from Wikipedia, the leading user-contributed encyclopedia. It may not have been reviewed by professional editors (see full disclaimer)

Dansk (Danish)
n. - laktose, mælkesukker

Nederlands (Dutch)
lactose (melksuiker)

Français (French)
n. - lactose

Deutsch (German)
n. - (Chem.) Lactose, Milchzucker

Ελληνική (Greek)
n. - λακτόζη, γαλακτοσάκχαρο

Italiano (Italian)
lattosio

Português (Portuguese)
n. - lactose (f) (Quím.)

Русский (Russian)
лактоза

Español (Spanish)
n. - lactosa

Svenska (Swedish)
n. - laktos, mjölksocker

中文（简体） (Chinese (Simplified))
乳糖

中文（繁體） (Chinese (Traditional))
n. - 乳糖

한국어 (Korean)
n. - 유당

日本語 (Japanese)
n. - ラクトース

العربيه (Arabic)
‏(الاسم) اللكتوز, سكر اللبن‏

עברית (Hebrew)
n. - ‮סוכר חלב, לקטוז‬

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