The structure and function of carbohydrates.

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The structure and function of carbohydrates

Carbohydrates are a widely diverse group of compounds that are common in nature. Chemically, carbohydrates are molecules that are composed of carbon, along with hydrogen and oxygen - usually in the same ratio as that found in water (H2O). Typical carbohydrates are composed of strings or chains of monosaccharides - that is, chains of individual sugars. A monosaccharide (mono = one, saccharide = sugar) is the smallest carbohydrate unit. The type of monosaccharides in the chain, length of the chain, and method of linking all determine the composition of the carbohydrate.

A listing of some of the saccharides include:        

  • Monosaccharides - single molecules, usually with 5 or 6 carbons
  • pentoses - sugars with 5 carbons, including arabinose, xylose, ribose
  • hexoses - sugars with 6 carbons, including glucose, fructose, galactose, mannose
  • Disaccharides - sugars containing 2 monosaccharides
  • sucrose - glucose + fructose
  • maltose - glucose + glucose
  • lactose - glucose + galactose
  • trisaccharides - combinations of three monosaccharides
  • polysaccharides - combinations of a large number of monosaccharides into complex threedimensional forms.
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     Examples include:

  1. glycogen - three dimensional strings of glucose that is produced by the liver and stored in liver and muscles. Glycogen serves as a glucose reserve for animals.
  2. starch - three dimensional strings of glucose stored in plants. Like glycogen, starch is one of the glucose reserves used in plants. It is highly digestible by animals and is a ready source of glucose.
  3. cellulose - Linear chains of glucose produced by plants. The glucoses in cellulose are linked together differently than starch, that changes the properties of the molecule. Cellulose cannot be digested by enzymes ...

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