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Monosaccharides


Monosaccharides

The most common naturally occuring mono saccharides are D-glucose, D-mannose, D-fructose and D-galactose among hexoses; and D-zylose and L – arabinose among pentoses. In a special sense, D-ribose and 2 deoxy-D-ribose are because they form the carbohydrate component of  (RNA) and deoxyribonucleic acid (DNA) respectively; these sugars are present in all  cells as components o nucleic acids. D-xylose found in most plants in the form of a polysacchrides called Xylan. D-galactose, a common constituent of both oligo-saccharides and alactose in animals occurs through intermediate compounds derived directly from glucose, animals do not require galactose in the diet. D -glucose, the naturally occurring form is found in fruits, honey, blood and under abnormal conditions, in urin
It also a constituent of the two most common naturally found disaccharides sucrose and lactose, as well as the exclusive structural unit of the polysaccharides cellulose, starch and glycogen. D-fructose, a ketohexose, is one of the constituents of the disaccharide sucrose and also found in uncombined form in honey, apples and tomatoes.
Fructose generally considered the sweetest monosaccharide is prepared by sucrose hydrolysis, and is metabolised by man Sugar alcohols of commercial importance are sorbitol (D-glucitol), commonly used as a sweetening agent, and D-mannitol also used as a sweetner particularly in chewing gums, because it has a limited water solubility and remain powdery and granular on long storage.

Among the the wide variety of naturally occuring glycosides are number of plant pigments, particularily those red, violet and blue in colour, these pigments a pigment are found in flowers and consist of molecule attached to sugar molecule, frequently glucose, Plant indican (from Indigofera species) of glucose and the pigments indoxyl. important the of indigo dye before timulants that digitalis is still used. Other naturally occurring which found  illa bean, and amygdalin (oil of bitariety of glucosides found in mustard. A number important antibiotic the best known are streptomycin and erythromycin.

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