1. Energy Storage:
* Starch (plants): The primary energy storage molecule in plants. It's a branched polymer of glucose, easily broken down for energy when needed.
* Glycogen (animals): The primary energy storage molecule in animals. It's a highly branched polymer of glucose, providing a quick energy source for muscles and other tissues.
2. Structural Support:
* Cellulose (plants): The most abundant organic compound on Earth, cellulose provides structural support to plant cell walls. Its rigid, linear structure forms strong fibers.
* Chitin (animals and fungi): A tough, flexible polysaccharide that makes up the exoskeletons of insects and crustaceans, and the cell walls of fungi.
* Peptidoglycan (bacteria): A complex polymer of sugars and amino acids that forms the rigid cell wall of bacteria. It's targeted by antibiotics like penicillin.
3. Lubrication and Protection:
* Hyaluronic acid (animals): A major component of synovial fluid, which lubricates joints, and also found in connective tissues like cartilage and skin.
* Heparin (animals): A complex polysaccharide that prevents blood clotting and plays a role in the immune system.
4. Recognition and Cell Signaling:
* Glycoproteins: Proteins with attached carbohydrate chains (polysaccharides). These sugars play crucial roles in cell-cell recognition, adhesion, and signaling.
* Glycolipids: Lipids with attached carbohydrate chains. They are essential for cell signaling, immune response, and recognition of pathogens.
5. Other Functions:
* Dietary Fiber (plants): Insoluble polysaccharides that aid digestion and regulate bowel movements.
* Agar (algae): A gel-forming polysaccharide used in food, cosmetics, and scientific research.
* Dextran (bacteria): A glucose polymer used in medicine as a plasma expander and in dental adhesives.
In summary, polysaccharides are essential for life, contributing to energy storage, structural support, lubrication, protection, cell signaling, and many other crucial functions.
