This MedLibrary.org supplementary page on Aldopentose is provided directly from the open source Wikipedia as a service to our readers. Please see the note below on authorship of this content, as well as the Wikipedia usage guidelines. To search for other content from our encyclopedia supplement, please use the form below:
Related Sponsors
A pentose is a monosaccharide with five carbon atoms.
They either have an aldehyde functional group in position 1 (aldopentoses), or a ketone functional group in position 2 (ketopentoses).
The aldopentoses have three chiral centres ("asymmetric carbon atoms") and so 8 different stereoisomers are possible.
The 4 D-aldopentoses are:
CH=O CH=O CH=O CH=O | | | | HC-OH HO-CH HC-OH HO-CH | | | | HC-OH HC-OH HO-CH HO-CH | | | | HC-OH HC-OH HC-OH HC-OH | | | | CH2OH CH2OH CH2OH CH2OH D-Ribose D-Arabinose D-Xylose D-Lyxose
The ketopentoses have 2 chiral centres and therefore 4 possible stereoisomers — ribulose (L- and D-form) and xylulose (L- and D-form).
The D-isomers of both are known to occur naturally as is the L-isomer of xylulose:
CH2OH CH2OH | | C=O C=O | | HC-OH HO-CH | | HC-OH HC-OH | | CH2OH CH2OH D-Ribulose D-Xylulose
The aldehyde and ketone functional groups in these carbohydrates react with neighbouring hydroxyl functional groups to form intramolecular hemiacetals or hemiketals, respectively. The resulting ring structure is related to furan, and is termed a furanose. The ring spontaneously opens and closes, allowing rotation to occur about the bond between the carbonyl group and the neighbouring carbon atom — yielding two distinct configurations (α and β). This process is termed mutarotation.
Ribose is a constituent of RNA, and the related deoxyribose of DNA.
A polymer composed of pentose sugars is called a pentosan.
See also
 |
This biochemistry article is a stub. You can help Wikipedia by expanding it. |
|
|||||||||||||||||||||||||||||||||||||||||||||||||||
Wikipedia content modification information:
- This page was last modified on 27 September 2008, at 22:59.
Wikipedia Authorship and Review
Wikipedia content provided here is not reviewed directly by MedLibrary.org. Wikipedia content is authored by an open community of volunteers and is not produced by or in any way affiliated with MedLibrary.org.
Wikipedia Usage Guidelines
This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article on "Aldopentose".
The URL for this specific entry is:
All Wikipedia text is available under the terms of the GNU Free Documentation License. (See Copyrights for details). Wikipedia® is a registered trademark of the Wikimedia Foundation, Inc.