During this essay I will look look at the biological importance of polysaccharides and what makes them so important for us, by looking into the structure the bonding types and chemical properties of polysaccharides.
Polysaccharides are repeating units of carbohydrates or chains of monosaccharides joint together by various glycosidic bonds . These covalent bonds form after condensation reaction takes place as the monosccharides bond. These chains can be branched or unbranched.
These long chains are insoluble, and have the general formula of Cn(H2O)n-1 .
We divide polysaccharides into two group : Storage polysaccharides and Structural polysaccharides.
Starch is an storage polysaccharides made up of alpha glucose molecules. These alpha glucose molecules are made up of two components : Amylose and Amylopectin. Amylose is about 300 glucose molecules joint together by an alpha 1-4 glycosidic bond, but the CH2OH would not fit if the ...view middle of the document...
Starch is the main carbohydrate food store in plants. And the plant stores excess glucose as starch because it is compact so one molecule of starch is equal to many molecules of glucose, this also lowers the osmotic gradient in the cell. As glucose it could leave the cell and starch is not very reactive however it can easily be turned into a sugar by hydrolysing it. Humans have amylase, which helps to digest the starch, so foods like potato , rice and wheat are a major part of our diet.
Glycogen is the polysaccharide that is used by animals for storing glucose for future use. It is similar to amylopectin as it contains alpha 1-4 and 1-6 glycosidic bonds but they branch more often. This is important in animals as animals are required to move and the more branched a molecule is the more ends it has for enzymes to work on and to hydrolyse the glycogen to form glucose. This therefore means that a faster energy supply is available. It is mostly stored in the liver and muscles.
The major component in cell walls in plants is cellulose, it is the most common organic compound on earth. Cellulose is a structural polysaccharide and it is a polymer of beta glucose with beta 1-4 glycosidic bond. Because it's a beta glucose the middle glucose needs to be flipped around, therefore making cellulose a straight chain molecule.
Parallel chains will hydrogen bond trough the hydroxylic group, and successive layers of microfibrils are laid down in different directions in the cell wall providing great tension, this strength is important in cell walls.
Another important polysacharide is Chitin, it is a long-chain polymer of a N-acetylglucosamine and an added amino acid, taking it strong and light. This is ideal for the exoskeleton of arthropods and cell walls of fungi. Like cellulose it is joint by beta 1-4 glycosidic bond.
On the whole polysaccharides carry out many different functions in biology , from making up the most important food source to providing a good exoskeleton for crabs. And I've found that almost all of it depends on the structure , the type of glycocidic bond and the type of monomer they are made of.