Disaccharide

A disaccharide or biose[1] is the carbohydrate formed when two monosaccharides undergo a condensation reaction which involves the elimination of a small molecule, such as water, from the functional groups only. Like monosaccharides, disaccharides form an aqueous solution when dissolved in water. One of the more known examples is sucrose, the other lactose.[2]

'Disaccharide' is one of the four chemical groupings of carbohydrates (monosaccharide, disaccharide, oligosaccharide, and polysaccharide).

Contents

Classification

There are two different types of disaccharides: reducing disaccharides, in which one monosaccharide, the reducing sugar, still has a free hemiacetal unit; and non-reducing disaccharides, in which the components bond through an acetal linkage between their anomeric centers and neither monosaccharide has a free hemiacetal unit. Cellobiose and maltose are examples of reducing disaccharides. Sucrose and trehalose are examples of non-reducing disaccharides. [3] [4]

Formation

Disaccharides are formed when two monosaccharides are joined together and a molecule of water is removed. For example; milk sugar (lactose) is made from glucose and galactose whereas the sugar from sugar cane and sugar beets (sucrose) is made from glucose and fructose.[citation needed]

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.[citation needed]

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
Sucrose (table sugar, cane sugar, beet sugar, or saccharose) glucose fructose α(1→2)β
Lactulose galactose fructose β(1→4)
Lactose (milk sugar) galactose glucose β(1→4)
Maltose glucose glucose α(1→4)
Trehalose glucose glucose α(1→1)α
Cellobiose glucose glucose β(1→4)

Maltose and cellobiose are hydrolysis products of the polysaccharides, starch and cellulose, respectively.

Less common disaccharides include:[5]

Disaccharide Units Bond
Kojibiose two glucose monomers α(1→2) [6]
Nigerose two glucose monomers α(1→3)
Isomaltose two glucose monomers α(1→6)
β,β-Trehalose two glucose monomers β(1→1)β
α,β-Trehalose two glucose monomers α(1→1)β[7]
Sophorose two glucose monomers β(1→2)
Laminaribiose two glucose monomers β(1→3)
Gentiobiose two glucose monomers β(1→6)
Turanose a glucose monomer and a fructose monomer α(1→3)
Maltulose a glucose monomer and a fructose monomer α(1→4)
Palatinose a glucose monomer and a fructose monomer α(1→6)
Gentiobiulose a glucose monomer and a fructose monomer β(1→6)
Mannobiose[disambiguation needed ] two mannose monomers either α(1→2), α(1→3), α(1→4), or α(1→6)
Melibiose a galactose monomer and a glucose monomer α(1→6)
Melibiulose a galactose monomer and a fructose monomer α(1→6)
Rutinose a rhamnose monomer and a glucose monomer α(1→6)
Rutinulose a rhamnose monomer and a fructose monomer β(1→6)
Xylobiose two xylopyranose monomers β(1→4)

See also

References

  1. ^ Biose on www.merriam-webster.com
  2. ^ IUPAC, Compendium of Chemical Terminology, 2nd ed. (the "Gold Book") (1997). Online corrected version:  (2006–) "disaccharides".
  3. ^ "Nomenclature of Carbohydrates (Recommendations 1996)2-Carb-36 Disaccharides.". http://www.chem.qmul.ac.uk/iupac/2carb/36.html. 
  4. ^ "Disaccharides and Oligiosaccharides". http://faculty.virginia.edu/mcgarveylab/Carbsyn/Carblist/html/disacch.html. Retrieved 2008-01-29. 
  5. ^ F.W.Parrish; W.B.Hahn,G.R.Mandels (July 1968). "Crypticity of Myrothecium verrucaria Spores to Maltose and Induction of Transport by Maltulose, a Common Maltose Contaminant". J. Bacteriol. (American Society for Microbiology) 96 (1): 227–233. PMC 252277. PMID 5690932. http://jb.asm.org/cgi/reprint/96/1/227.pdf. Retrieved 2008-11-21. 
  6. ^ Matsuda, K.; Abe, Y; Fujioka, K (November 1957). "Kojibiose (2-O-alpha-D-Glucopyranosyl-D-Glucose): Isolation and Structure: Chemical Synthesis". Nature 180 (4593): 985–6. doi:10.1038/180985a0. PMID 13483573. 
  7. ^ T. Taga; Y. Miwa, Z. Min (1997). "α,β-Trehalose Monohydrate". Acta Cryst. C53 (2): 234–236. doi:10.1107/S0108270196012693. http://scripts.iucr.org/cgi-bin/paper?S0108270196012693. 

External links


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Look at other dictionaries:

  • disaccharide — [ disakarid ] n. m. • 1949; de di et saccharide ♦ Sucre formé par condensation de deux monosaccharides avec élimination d une molécule d eau. Le saccharose, le lactose et le maltose sont des disaccharides. ⇒ diholoside. ● disaccharide nom… …   Encyclopédie Universelle

  • Disaccharide — (Saccharobiosen), s. Biosen …   Lexikon der gesamten Technik

  • Disaccharide — ⇒ Oligosaccharide …   Deutsch wörterbuch der biologie

  • disaccharide — [dī sak′ə rīd΄] n. any of a group of sugars with a common formula, C12H22O11, as sucrose, maltose, and lactose, which on hydrolysis yield two monosaccharides: see OLIGOSACCHARIDE …   English World dictionary

  • Disaccharide — Saccharose (Rohrzucker), das am häufigsten vorkommende Disaccharid aus Glucose und Fructose welche 1,2 verknüpft sind Disaccharide (veraltet Zweifachzucker) sind organisch chemische Verbindungen aus der Gruppe der Kohlenhydrate mit der… …   Deutsch Wikipedia

  • disaccharide — /duy sak euh ruyd , rid/, n. Chem. any of a group of carbohydrates, as sucrose or lactose, that yield monosaccharides on hydrolysis. Also called double sugar. [1890 95; DI 1 + SACCHARIDE] * * * ▪ biochemistry also called  Double Sugar,    any… …   Universalium

  • disaccharide — disacharidas statusas T sritis chemija apibrėžtis Du monosacharidai, susijungę glikozidiniu ryšiu. atitikmenys: angl. disaccharide rus. дисахарид …   Chemijos terminų aiškinamasis žodynas

  • disaccharide — noun Date: 1889 any of a class of sugars (as sucrose) that yields on hydrolysis two monosaccharide molecules …   New Collegiate Dictionary

  • Disaccharide — Diholoside Le saccharose, est un diholoside formé par 2 oses : le D glucose (à gauche) et le D fructose (à droite). Les diholosides sont des sucres formés par deux oses (sucres simples non hydrolysables). Si l on suit une nomenclature… …   Wikipédia en Français

  • disaccharide — Sugar formed from two monosaccharide units linked by a glycosidic bond. The trehalose type are formed from two non reducing sugars, the maltose type from two reducing sugars …   Dictionary of molecular biology

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