Xylose (Molecule of the Month for March 2020)
Xylose is a sugar first isolated from wood, and named for it. Xylose is classified as a monosaccharide of the aldopentose type, which means that it contains five carbon atoms and includes an aldehyde functional group. It is derived from hemicellulose, one of the main constituents of plant biomass. Like most sugars, it can adopt several structures depending on conditions. With its free aldehyde group, it is a reducing sugar. Xylose is the main building block for the hemicellulose xylan, which comprises about 30% of some plants (birch for example), far less in others (spruce and pine have about 9% xylan). It was first isolated from wood by Finnish scientist, Koch, in 1881.
The cyclic hemiacetal isomers are more prevalent in solution and are of two types: the pyranoses, which feature six-membered C5O rings, and the furanoses, which feature five-membered C4O rings (with a pendant CH2OH group). Each of these rings is subject to further isomerism, depending on the relative orientation of the anomeric hydroxy group. The dextrorotary form, d-xylose, is the one that usually occurs endogenously in living things.
Xylose is metabolised by humans, although it is not a major human nutrient and is largely excreted by the kidneys. Humans can obtain xylose only from their diet.
Formal Chemical Name (IUPAC)
Update by Karl Harrison
(Molecule of the Month for March 2020 )
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