Monday, March 17, 2008


Monosaccharides are , as the name implies, the simplest of the carbohydrate. This classifications includes a series of aldehydes (aldoses) and ketones (ketoses) grouped according to the number of carbon atoms in the chain: trioses, tetroses, pentoses, hexoses, and heptoses. These sugars may be definitely described according to structure and number of the carbon atoms as aldotrioses, ketetrioses, and so on.

With the possible exception of the hexoses, monosaccharides are of little dietary significance. Both glucose and fructose have long been known to occur in free from on certain fruits and in honey.

Small amounts of mannose have been also detected in a few fruits. However it appears at present that only the pentoses and hexoses play fundamental roles in cellularmetabolism although trioses, tetroses, and sedoheptulose are important intermediate in the metabolism of carbohydrate in animal cells. Indeed, the simple triose, glyceraldehydes, is potentially the building block of all cell carbohydrates as will be seen in carbohydrate metabolism.

Pentose sugars are readily synthesized in the cell. Ribose is the most important of the pentoses in biological systems and can be converted to deoxyribose and ribitol, neither of which can be classified strictly as a carbohydrate. Deoxyribose has two nitrogen atoms attached to carbon atom 2, instead of one hydrogen atom and one hydroxyl group. Both ribose and deoxyribose are constituent of a nucleic acid that bears their name : ribonucleic acid (RNA) and deoxyribonucleic acid (DNA).
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