Disaccharide
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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).
Contents |
Formation
It is formed when two sugars are joined together and a molecule of water is removed. For example; milk sugar (lactose) is made from glucose and galactose whereas cane sugar (sucrose) is made from glucose and fructose.
The two monosaccharides are bonded via a dehydration reaction (also called a condensation reaction or dehydration synthesis) that leads to the loss of a molecule of water and formation of a glycosidic bond.
Properties
The glycosidic bond can be formed between any hydroxyl group on the component monosaccharide. So, even if both component sugars are the same (e.g., glucose), different bond combinations (regiochemistry) and stereochemistry (alpha- or beta-) result in disaccharides that are diastereoisomers with different chemical and physical properties.
Depending on the monosaccharide constituents, disaccharides are sometimes crystalline, sometimes water-soluble, and sometimes sweet-tasting and sticky-feeling.
Common disaccharides
| Disaccharide | Unit 1 | Unit 2 | Bond | Disaccharidase |
| Sucrose (table sugar, cane sugar, saccharose, or beet sugar) | glucose | fructose | α(1→2) | sucrase |
| Lactose (milk sugar) | galactose | glucose | β(1→4) | lactase |
| Maltose | glucose | glucose | α(1→4) | maltase |
| Trehalose | glucose | glucose | α(1→1)α | trehalase |
| Cellobiose | glucose | glucose | β(1→4) | cellobiase |
Maltose and cellobiose are hydrolysis products of the polysaccharides, starch and cellulose, respectively.
Less common disaccharides include: Gentiobiose, that consists of two glucose monomers with an β(1→6) linkage; Isomaltose, that consists of two glucose monomers with an α(1→6) linkage; Kojibiose, that consists of two glucose monomers with an α(1→2) linkage [2]; Laminaribiose, that consists of two glucose monomers with a β(1→3) linkage; Mannobiose, that consists of two mannose monomers with either an α(1→2), α(1→3), α(1→4), or an α(1→6) linkage; Melibiose, that consists of a glucose monomer and a galactose monomer with an α(1→6) linkage; Nigerose, that consists of two glucose monomers with an α(1→3) linkage; Rutinose, that consists of a rhamnose monomer and a glucose monomer with an α(1→6) linkage; and Xylobiose, that consists of two xylopyranose monomers with a β(1→4) linkage.
References
- ↑ International Union of Pure and Applied Chemistry. "disaccharides". Compendium of Chemical Terminology Internet edition.
- ↑ Matsuda, K. (November 1957). "Kojibiose (2-O-alpha-D-Glucopyranosyl-D-Glucose): Isolation and Structure: Chemical Synthesis". Nature 180: 985. doi:10.1038/180985a0.
External links
ar:سكريات ثنائيةbg:Дизахарид de:Zweifachzucker et:Disahhariidideo:Disakarido eu:Disakaridoit:Disaccaridi he:דו-סוכר la:Disaccharides lt:Disacharidas mk:Дисахарид ms:Disakarida nl:Disacharideno:Disakkaridsimple:Disaccharide fi:Disakkaridi sv:Disackarider th:ไดแซ็กคาไรด์ uk:Дисахариди
Acknowledgement and Attribution Regarding Sources of Content
Some of the initial content on this page may be incorporated in part from copyleft sources in the public domain including wikis such as Wikipedia and AskDrWiki. Drug information for patients came from the The National Library of Medicine. Infectious disease information may have come from the Centers for Disease Control (CDC). Differential Diagnoses are drawn from clinicians as well as an amalgamation of 3 sources: 1.The Disease Database; 2. Kahan, Scott, Smith, Ellen G. In A Page: Signs and Symptoms. Malden, Massachusetts: Blackwell Publishing, 2004:3; 3. Sailer, Christian, Wasner, Susanne. Differential Diagnosis Pocket. Hermosa Beach, CA: Borm Bruckmeir Publishing LLC, 2002:7 .
