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carbohydrates

Thursday 21 May 2009

Definition: Carbohydrates are straight-chain aldehydes or ketones with many hydroxyl groups that can exist as straight chains or rings.

Carbohydrates are the most abundant biological molecules, and fill numerous roles, such as the storage and transport of energy (starch, glycogen) and structural components (cellulose in plants, chitin in animals).

The basic carbohydrate units are called monosaccharides and include galactose, fructose, and most importantly glucose.

Monosaccharides can be linked together to form polysaccharides in almost limitless ways.

- Monosaccharides are the simplest form of carbohydrates with only one simple sugar. They essentially contain an aldehyde or ketone group in their structure. Examples of monosaccharides are the hexoses glucose, fructose, and galactose and pentoses, ribose, and deoxyribose

- Disaccharides are formed when two monosaccharides, or two single simple sugars, form a bond with removal of water. Examples of disaccharides include sucrose, maltose, and lactose

- Polysaccharides are polymerized monosaccharides, complex, carbohydrates. They have multiple simple sugars. Examples are starch, cellulose, and glycogen. They are generally large and often have a complex branched connectivity. Shorter polysaccharides, with 2 - 10 monomers, are called oligosaccharides.

See also

- complex carbohydrates
- carbohydrate metabolism