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[[File:D-Glyceraldehyde 2D Fischer.svg|thumb|140px|[[Fischer projection]] of {{smallcaps all|D}}-[[glyceraldehyde]]]] |
[[File:D-Glyceraldehyde 2D Fischer.svg|thumb|140px|[[Fischer projection]] of {{smallcaps all|D}}-[[glyceraldehyde]]]] |
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An '''aldose''' is a [[monosaccharide]] (a simple sugar) that contains only one [[aldehyde]] (−CH=O) group per [[molecule]]. The [[chemical formula]] takes the form C<sub>''n''</sub>(H<sub>2</sub>O)<sub>''n''</sub>. The simplest possible aldose is the [[diose]] [[glycolaldehyde]], which only contains two [[carbon]] [[atom]]s.<ref>{{cite book| last=Berg| first=J.M.| edition=6th| title=Biochemistry| year=2006| publisher=W. H. Freeman and Company| location=New York}}</ref> |
An '''aldose''' is a [[monosaccharide]] (a simple sugar) that contains only one [[aldehyde]] (−CH=O) group per [[molecule]]. The [[chemical formula]] takes the form C<sub>''n''</sub>(H<sub>2</sub>O)<sub>''n''</sub>. The simplest possible aldose is the [[diose]] [[glycolaldehyde]], which only contains two [[carbon]] [[atom]]s.<ref>{{cite book| last=Berg| first=J.M.| edition=6th| title=Biochemistry| year=2006| publisher=W. H. Freeman and Company| location=New York}}</ref> |
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Because they have at least one asymmetric carbon center, aldoses with three or more carbon atoms exhibit [[stereoisomerism]]. Aldoses containing stereogenic centers can exist in either a {{smallcaps all|D}}- form or {{smallcaps all|L}}- form. The determination is made based on the chirality of the penultimate carbon (the second-furthest from the aldehyde), where alcohol groups on the right of the [[Fischer projection]] result in {{smallcaps all|D}}-aldoses, and [[epimer]]s with alcohols on the left result in {{smallcaps all|L}}-aldoses. Biological systems tend to recognize {{smallcaps all|D}}-aldoses more than {{smallcaps all|L}}-aldoses. |
Because they have at least one asymmetric carbon center, aldoses with three or more carbon atoms exhibit [[stereoisomerism]]. Aldoses containing stereogenic centers can exist in either a {{smallcaps all|D}}- form or {{smallcaps all|L}}- form. The determination is made based on the chirality of the penultimate carbon (the second-furthest from the aldehyde), where alcohol groups on the right of the [[Fischer projection]] result in {{smallcaps all|D}}-aldoses, and [[epimer]]s with alcohols on the left result in {{smallcaps all|L}}-aldoses. Biological systems tend to recognize {{smallcaps all|D}}-aldoses more than {{smallcaps all|L}}-aldoses. |
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An aldose differs from a [[ketose]] in that it has a [[carbonyl]] group at the end of the carbon chain instead of in the middle. This allows ketoses and aldoses to be chemically differentiated through [[Seliwanoff's test]].<ref>{{cite web|title=Seliwanoff's Test| publisher=Harper College| accessdate=2011-07-10| url=http://www.harpercollege.edu/tm-ps/chm/100/dgodambe/thedisk/carbo/seli/seli.htm}}</ref> An aldose may [[isomer]]ize to a ketose through the [[Lobry-de Bruyn-van Ekenstein transformation]]. |
An aldose differs from a [[ketose]] in that it has a [[carbonyl]] group at the end of the carbon chain instead of in the middle. This allows ketoses and aldoses to be chemically differentiated through [[Seliwanoff's test]].<ref>{{cite web|title=Seliwanoff's Test| publisher=Harper College| accessdate=2011-07-10| url=http://www.harpercollege.edu/tm-ps/chm/100/dgodambe/thedisk/carbo/seli/seli.htm}}</ref> An aldose may [[isomer]]ize to a ketose through the [[Lobry-de Bruyn-van Ekenstein transformation]]. |
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==List of aldoses== |
==List of aldoses== |
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Revision as of 18:36, 11 September 2015
An aldose is a monosaccharide (a simple sugar) that contains only one aldehyde (−CH=O) group per molecule. The chemical formula takes the form Cn(H2O)n. The simplest possible aldose is the diose glycolaldehyde, which only contains two carbon atoms.[1]
Because they have at least one asymmetric carbon center, aldoses with three or more carbon atoms exhibit stereoisomerism. Aldoses containing stereogenic centers can exist in either a D- form or L- form. The determination is made based on the chirality of the penultimate carbon (the second-furthest from the aldehyde), where alcohol groups on the right of the Fischer projection result in D-aldoses, and epimers with alcohols on the left result in L-aldoses. Biological systems tend to recognize D-aldoses more than L-aldoses.
An aldose differs from a ketose in that it has a carbonyl group at the end of the carbon chain instead of in the middle. This allows ketoses and aldoses to be chemically differentiated through Seliwanoff's test.[2] An aldose may isomerize to a ketose through the Lobry-de Bruyn-van Ekenstein transformation.
List of aldoses
- Diose: glycolaldehyde
- Triose: glyceraldehyde
- Tetroses: erythrose, threose
- Pentoses: ribose, arabinose, xylose, lyxose
- Hexoses: allose, altrose, glucose, mannose, gulose, idose, galactose, talose
See also
References
- ^ Berg, J.M. (2006). Biochemistry (6th ed.). New York: W. H. Freeman and Company.
- ^ "Seliwanoff's Test". Harper College. Retrieved 2011-07-10.
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