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Information about Lactose

Lactose
Identifiers
CAS number63-42-3
PubChem6134
MeSHLactose
Properties
Molecular formulaC12H22O11
Molar mass342.296
Except where noted otherwise, data are given for
materials in their standard state
(at 25 C, 100 kPa)
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, 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

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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 CarbohydratesAnalogues of nucleic acids:
General: Aldose | Ketose | Pyranose | Furanose
Geometry: Pentose | Hexose | Heptose | Cyclohexane conformation | Anomer | Mutarotation
Small/Large: Glyceraldehyde | Dihydroxyacetone | Erythrose | Threose | Erythrulose | Sedoheptulose
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
CAS registry numbers are unique numerical identifiers for chemical compounds, polymers, biological sequences, mixtures and alloys. They are also referred to as CAS numbers, CAS RNs or CAS #s.
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PubChem is a database of chemical molecules. The system is maintained by the National Center for Biotechnology Information (NCBI), a component of the National Library of Medicine, which is part of the United States National Institutes of Health (NIH).
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Medical Subject Headings (MeSH) is a huge controlled vocabulary (or metadata system) for the purpose of indexing journal articles and books in the life sciences. Created and updated by the United States National Library of Medicine (NLM), it is used by the MEDLINE/PubMed
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A chemical formula is a concise way of expressing information about the atoms that constitute a particular chemical compound. A chemical formula is also a short way of showing how a chemical reaction occurs.
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4, 2
(mildly acidic oxide)
Electronegativity 2.55 (Pauling scale)
Ionization energies
(more) 1st: 1086.5 kJmol−1
2nd: 2352.6 kJmol−1
3rd: 4620.5 kJmol−1

Atomic radius 70 pm
Atomic radius (calc.
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1, −1
(amphoteric oxide)
Electronegativity 2.20 (Pauling scale) More

Atomic radius 25 pm
Atomic radius (calc.) 53 pm
Covalent radius 37 pm
Van der Waals radius 120 pm
Miscellaneous

Thermal conductivity (300 K) 180.
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2, −1
(neutral oxide)
Electronegativity 3.44 (Pauling scale)
Ionization energies
(more) 1st: 1313.9 kJmol−1
2nd: 3388.3 kJmol−1
3rd: 5300.5 kJmol−1

Atomic radius 60 pm
Atomic radius (calc.
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Molar mass, symbol M,[1] is the mass of one mole of a substance (chemical element or chemical compound).[2] It is a physical property which is characteristic of each pure substance.
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standard state of a material is its state at 1 bar (100 kilopascals exactly). This pressure was changed from 1 atm (101.325 kilopascals) by IUPAC in 1990.[1] The standard state of a material can be defined at any given temperature, most commonly 25 degrees Celsius,
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A disaccharide is a sugar (a carbohydrate) composed of two monosaccharides.[1]

'Disaccharide' is one of the four chemical groupings of carbohydrates (monosaccharide, disaccharide, oligosaccharide, and polysaccharide).
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Galactose (Gal) (also called brain sugar[1]) is a type of sugar which is less sweet than glucose and not very water-soluble. It is considered a nutritive sweetener because it has food energy.

Galactan is a polymer of the sugar galactose.
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Glucose (Glc), a monosaccharide (or simple sugar), is an important carbohydrate in biology. The living cell uses it as a source of energy and metabolic intermediate.
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In chemistry, a glycosidic bond is a certain type of functional group that joins a carbohydrate (sugar) molecule to an alcohol, which may be another carbohydrate. Specifically, a glycosidic bond is formed between the hemiacetal group of a saccharide (or a molecule derived from a
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Milk is an opaque white liquid produced by the mammary glands of female mammals (including monotremes). Mammary glands are highly specialized sweat glands. The female ability to produce milk is one of the defining characteristics of mammals.
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Latin}}} 
Official status
Official language of: Vatican City
Used for official purposes, but not spoken in everyday speech
Regulated by: Opus Fundatum Latinitas
Roman Catholic Church
Language codes
ISO 639-1: la
ISO 639-2: lat
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Lactose intolerance
Classification & external resources

Lactose, a disaccharide of β-D-galactose &
β-D-glucose, that is normally split by lactase.
ICD-10 E 73.
ICD-9 271.
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Mammalia
Linnaeus, 1758

Subclasses & Infraclasses
  • Subclass †Allotheria*
  • Subclass Prototheria
  • Subclass Theria

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Enzymes are proteins that catalyze (i.e. accelerate) chemical reactions.[1] In enzymatic reactions, the molecules at the beginning of the process are called substrates, and the enzyme converts them into different molecules, the products.
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Lactase (LCT), a member of the β-galactosidase family of enzymes, is a glycoside hydrolase involved in the hydrolysis of the disaccharide lactose into constituent galactose and glucose monomers.
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Villus (Latin: "shaggy hair"[1], plural villi) can refer to:
  • Intestinal villus. This is the most common meaning when not more precisely specified
  • Chorionic villi, found on the surface of the outermost membrane (the chorion) of the fetus

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Glucose (Glc), a monosaccharide (or simple sugar), is an important carbohydrate in biology. The living cell uses it as a source of energy and metabolic intermediate.
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Galactose (Gal) (also called brain sugar[1]) is a type of sugar which is less sweet than glucose and not very water-soluble. It is considered a nutritive sweetener because it has food energy.

Galactan is a polymer of the sugar galactose.
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Europe is one of the seven traditional continents of the Earth. Physically and geologically, Europe is the westernmost peninsula of Eurasia, west of Asia. Europe is bounded to the north by the Arctic Ocean, to the west by the Atlantic Ocean, to the south by the Mediterranean Sea,
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Middle East is a historical and political region of Africa-Eurasia with no clear boundaries. The term "Middle East" was popularized around 1900 in Britain, and has been criticized for its loose definition.
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C. a. hircus

Trinomial name
Capra aegagrus hircus
(Linnaeus, 1758)

The domestic goat (Capra aegagrus hircus) is a domesticated subspecies of the wild goat of southwest Asia and Eastern Europe.
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The Paleolithic diet (abbreviated Paleo diet) is also known as the Caveman diet, Prehistoric diet, Stone Age diet, or Hunter-gatherer diet.
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ice age is a period of long-term reduction in the temperature of Earth's climate, resulting in an expansion of the continental ice sheets, polar ice sheets and mountain glaciers.
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