Polysaccharides
Polysaccharides are a large class of carbohydrates that consist of long chains of monosaccharide units joined together by glycosidic linkages. These are the most abundant carbohydrates found in nature and serve crucial functions in biological systems. They can be classified primarily into three types: storage polysaccharides, structural polysaccharides, and some that fulfill both roles.
- Starch: As the main storage polysaccharide in plants, starch is vital for energy storage. Composed of two components—amylose (a linear polymer of α-D-glucose) and amylopectin (a branched polymer of α-D-glucose)—it is predominantly found in grains, tubers, and various vegetables.
- Cellulose: Unlike starch, cellulose is mainly found in plant cell walls and is structured exclusively from β-D-glucose units linked by glycosidic bonds. This configuration provides rigidity and strength to plant cells, making cellulose the most abundant organic molecule on Earth.
- Glycogen: In animals, glycogen serves as the primary storage form of carbohydrates. It shares a similar structure to amylopectin but is more highly branched, allowing for rapid mobilization of glucose when energy is required. Glycogen is stored in the liver and muscles and can be quickly converted back to glucose.
The diverse structures and functions of polysaccharides underscore their importance in biological systems, acting not only as energy reserves but also contributing to cellular integrity.