Carbohydrate Nomenclature

Carbohydrate Nomenclature - Carbohydrate Nomenclature I....

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Carbohydrate Nomenclature I. Monosaccharides Taming the Mayhem We may think of carbohydrates as sugar and spice and everything nice, but, to first year biochemistry students, carbohydrates are a terror. One reason is the nomenclature for the monosaccharides. A comprehensive nomenclature is needed to obtain precision in a classification scheme, distinguishing one sugar from another when only subtle differences exist between the two. Organic chemistry gives us terms such as D and L isomers, chiral centers, enantiomers, diastereoisomers, etc. Biochemical terminology builds on the organic using terms such as anomers, alpha and beta sugars, glycosides, oligosaccharides, all attempting to signify uniqueness in the complexity of the structures. Sprinkled in among the vocabulary are specific names of sugars, e.g., glucose, maltose, amylopectin, that can be as daunting to learn as the structures. This tutorial is designed to point out features that will help you remember the structures and names of this all-important class of biomolecules.
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Numbers, Groups and Names “OSE” is the suffix denoting a sugar and “ULOSE” denotes a keto sugar. The monosaccharides you will encounter in biochemistry have 3, 4, 5, 6, and 7 carbons. Prefixes such as tri, tetra, penta, hexa, and hepta alert you to the number. Know these prefixes ( click 1 ). You will also see “aldo” and “keto” to denote the type of functional group ( click 1 ). The term aldopentose denotes two structural features, chain length and functional group. Aldo refers to aldehyde and keto to ketone. The figures show an aldopentose and a ketohexose. C C C Tri- C C C C Tetra- C C C C C Penta- C C C C C C Hexa- C C C C C C C Hepta- C C C C C O H Aldopentose C C=O C C C C Ketohexose An aldo sugar always has the “carbonyl” group on C-1, a keto sugar has it on C-2. This is good to remember. –OH groups are not indicated by this terminology. More terms are need, therefore, to describe a specific sugar. Click to go on.
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Balls and Sticks: All sugars have one carbonyl group and at least two –OH groups. All have at least one –CH 2 OH group. What distinguishes one from another is the right-left orientations of internal –OH groups. Stereochemistry is best learned by using balls and sticks. For example, D-glucose, an aldohexose, is show as (
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This note was uploaded on 04/25/2010 for the course BIOCHEM 153A taught by Professor Abbot during the Spring '10 term at UCLA.

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Carbohydrate Nomenclature - Carbohydrate Nomenclature I....

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