carbo review

carbo review - Carbohydrates Know the general features and...

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Carbohydrates Know the general features and roles of carbohydrate molecules • At least one, often more, asymmetric (chiral) centers • Linear and ring structures • Can form polymers through  glycosidic  bonds • Can form multiple hydrogen bonds with water and other molecules Major form of stored energy Know the difference between aldoses and ketoses •  Aldoses  are monosaccharides that contain an aldehyde function. The simplest aldose is glyceraldehyde, which has two stereoisomers •  Ketoses  contain a ketone group, the simplest is dihydroxy-acetone Understand how the D/L designation of sugars is derived • The D/L designation refers to the configuration of the highest numbered asymmetric carbon, that is the one furthest from the carbonyl carbon • The isomer is D if the hydroxyl group on the highest numbered carbon is drawn on the right in a flat projection • Most naturally occurring carbohydrates are D isomers Understand how linear forms can cyclize to form a pyranose or a furanose The alcohol group of a carbohydrate can react with the aldehyde or ketone function to form a hemiacetal, this results in cyclization of the linear sugar, and generates an additional asymmetric center. The result is a six- or fivemembered ring containing oxygen, called a  pyranose  or a furanose • In aqueous solution, the pyranose and furanose are the preferred forms of monosaccharides Cyclized forms may have 2 stereoisomers called anomers • Cyclization of D-glucose generates a mixture of  α and ß isomers (called  anomers ) Pyranoses typically adopt chair or boat configurations Sugars can be derivatized to form sugar alcohols, deoxy sugars, and so on Monosaccharides can be converted to numerous derivatives: sugar acids, sugar alcohols, deoxy sugars, sugar esters, amino sugars, phospho sugars Elimination of water forms α or ß glycosidic bond Know some examples of disaccharides Cellobiose and maltose are of reducing. Sucrose and trehalose are of non-reducing.
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Starch is a polymer of amylose and amylopectin containing both 1,4 and 1,6 glycosidic bonds •  Amylose  is a linear chain of glucose units in  1,4 linkages
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carbo review - Carbohydrates Know the general features and...

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