Carbohydrates: Polysaccharides (A-level Biology)
Carbohydrates: Polysaccharides
Polysaccharides
- Polysaccharides are complex carbohydrates. Moving onwards from simple sugars (i.e. monosaccharides and disaccharides), we encounter a third class of sugar based compounds which we refer to as polysaccharides.
- Polysaccharides are made by condensation of many glucose units. Polysaccharides are polymers made up of multiple glucose monosaccharides. Like disaccharides, polysaccharides are made through condensation reactions between glucose monosaccharides, resulting in the formation of glycosidic bonds.
- Polysaccharides can be broken down by hydrolysis. Polysaccharides can be broken down into disaccharides or constituent monosaccharides via a hydrolysis reaction. This occurs when we test for carbohydrates using Benedict’s Test for non-reducing sugars (covered in the later tutorial 20 Testing for Carbohydrates).
There are different types of polysaccharides:
- Glycogen is made from α-glucose. Glycogen is branched and consists of many α-glucose monomers.
- Starch is made from α-glucose. Starch is also made from many α-glucose monomers. There are two types of starch: amylose (non-branched) and amylopectin (branched).
- Cellulose is made from β-glucose. Cellulose consists of non-branched β-glucose chains.
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