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A furanose is a collective term for carbohydrates that have a chemical structure that includes a five-membered ring system consisting of four carbon atoms and one oxygen atom. The name derives from its similarity to the oxygen heterocycle furan, but the furanose ring does not have double bonds.^[1]

Structural properties

The chemical structure of ribose in its furanose form. The wavy bond indicates a mixture of β-ribofuranose and α-ribofuranose.

The furanose ring is a cyclic hemiacetal of an aldopentose or a cyclic hemiketal of a ketohexose.

A furanose ring structure consists of four carbon and one oxygen atom with the anomeric carbon to the right of the oxygen. The highest numbered chiral carbon (typically to the left of the oxygen in a Haworth projection) determines whether or not the structure has a d-configuration or L-configuration. In an l-configuration furanose, the substituent on the highest numbered chiral carbon is pointed downwards out of the plane, and in a D-configuration furanose, the highest numbered chiral carbon is facing upwards.

The furanose ring will have either alpha or beta configuration, depending on which direction the anomeric hydroxy group is pointing. In a d-configuration furanose, alpha configuration has the hydroxy pointing down, and beta has the hydroxy pointing up. It is the opposite in an l-configuration furanose. Typically, the anomeric carbon undergoes mutarotation in solution, and the result is an equilibrium mixture of α and β configurations.

References

^ Reginald, Garrett; Grisham, Charles M. (2005). Biochemistry (3rd ed.). Cengage Learning. ISBN 0-534-49033-6.

Types of carbohydrates

General

Geometry

Monosaccharides

Dioses	Aldodiose Glycolaldehyde
Trioses	Aldotriose Glyceraldehyde Ketotriose Dihydroxyacetone
Tetroses	Aldotetroses Erythrose Threose Ketotetrose Erythrulose
Pentoses	Aldopentoses Arabinose Lyxose Ribose Xylose Ketopentoses Ribulose Xylulose Deoxy sugars Deoxyribose
Hexoses	Aldohexoses Allose Altrose Galactose Glucose Gulose Idose Mannose Talose Ketohexoses Fructose Psicose Sorbose Tagatose Deoxy sugars Fucose Fuculose Rhamnose
Heptoses	Ketoheptoses Mannoheptulose Sedoheptulose
Above 7	Octoses Nonoses Neuraminic acid

Multiple

Disaccharides	Cellobiose Isomaltose Isomaltulose Lactose Lactulose Maltose Sucrose Trehalose Turanose
Trisaccharides	Maltotriose Melezitose Raffinose
Tetrasaccharides	Stachyose
Other oligosaccharides	Acarbose Fructooligosaccharide (FOS) Galactooligosaccharide (GOS) Isomaltooligosaccharide (IMO) Maltodextrin
Polysaccharides	Beta-glucan Oat beta-glucan Lentinan Sizofiran Zymosan Cellulose Chitin Chitosan Dextrin / Dextran Fructose / Fructan Inulin Galactose / Galactan Glucose / Glucan Glycogen Hemicellulose Levan beta 2→6 Lignin Mannan Pectin Starch Amylopectin Amylose Xanthan gum

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Structural properties

See also

References