Polysaccharides
Polysaccharides
Polysaccharides (pronunciation: /ˌpɒliˈsækəraɪd/) are complex carbohydrates composed of long chains of monosaccharide units bound together by glycosidic linkages. This term is used in organic chemistry to describe a high molecular weight or "giant" carbohydrate that is made up of monosaccharides joined together by glycosidic bonds.
Etymology
The term "polysaccharide" comes from the Greek words "poly", meaning many, and "saccharide", meaning sugar. It was first used in the late 19th century to describe the complex carbohydrates that were being discovered in plants and animals.
Types of Polysaccharides
There are several types of polysaccharides, including:
- Starch: A polysaccharide produced by most green plants as an energy store. It is the most common carbohydrate in the human diet and is contained in large amounts in staple foods like potatoes, wheat, maize (corn), rice, and cassava.
- Glycogen: The storage form of glucose in animals and humans which is analogous to the starch in plants.
- Cellulose: A polysaccharide consisting of glucose monomers that reinforces the cell walls of most plants.
- Chitin: A linear polysaccharide composed of randomly distributed β-(1→4)-linked D-glucosamine (a derivative of glucose). It is a characteristic component of the cell walls of fungi, the exoskeletons of arthropods such as crustaceans and insects, and the scales of fish and lissamphibians.
Functions of Polysaccharides
Polysaccharides have a variety of functions in the biological systems they are found in. These include:
- Energy storage: Polysaccharides like starch and glycogen serve as energy storage units in plants and animals respectively.
- Structural support: Polysaccharides like cellulose and chitin provide structural support to cells and organisms.
- Recognition and signaling: Some polysaccharides have roles in cell-cell recognition and as signaling molecules.
External links
- Medical encyclopedia article on Polysaccharides
- Wikipedia's article - Polysaccharides
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