What are polysaccharides and how are they used?

December 15, 2025 •

3 min read

Polysaccharides are the most abundant carbohydrates found in nature, playing vital roles in organisms from bacteria to humans. But what are polysaccharides and how are they used? These complex carbohydrates are fundamental to energy storage, structural support, and cell communication.

Quick Summary

Polysaccharides are large carbohydrate molecules formed by long chains of monosaccharides joined by glycosidic bonds. These macromolecules serve as essential energy storage and structural components in organisms, with wide applications across various industries.

Key Points

Definition: Polysaccharides are large carbohydrate polymers composed of many smaller monosaccharide units linked by glycosidic bonds.
Two Primary Roles: They serve two main biological functions: energy storage (e.g., starch in plants, glycogen in animals) and structural support (e.g., cellulose in plants, chitin in insects).
Homopolysaccharides vs. Heteropolysaccharides: Polysaccharides can be classified based on whether they contain a single type of monosaccharide (homo-) or multiple types (hetero-).
Diverse Applications: They are widely used in the food industry as thickeners and gelling agents, in medicine for drug delivery and vaccines, and in other industries like textiles and paper.
Structure Dictates Function: The specific arrangement and branching pattern of a polysaccharide's monosaccharides determine its physical properties and ultimate function in nature and industry.

What Defines a Polysaccharide?

Polysaccharides are complex carbohydrates, also known as glycans, formed by numerous simple sugar units (monosaccharides) linked together by glycosidic bonds. Their structure can be linear or highly branched, which directly affects their properties and functions. Unlike simple sugars, polysaccharides are typically not sweet and are often insoluble in water due to their large size. They are classified as homopolysaccharides if they consist of only one type of monosaccharide (like glucose) or heteropolysaccharides if they contain two or more different monosaccharides or their derivatives.

Key Functions in Living Organisms

Polysaccharides are essential for life, fulfilling critical roles in various organisms.

Energy Storage

Polysaccharides are the primary means of storing energy long-term in many organisms. Their structure allows for efficient packing within cells, and this stored energy can be quickly accessed by breaking the glycosidic bonds through hydrolysis.

Starch: The main energy storage polysaccharide in plants, found in forms like amylose and amylopectin in seeds and roots.
Glycogen: The energy storage polysaccharide in animals, stored mainly in the liver and muscles. Its highly branched structure facilitates rapid glucose release for energy needs.

Structural Support

Many polysaccharides provide strength and rigidity, serving as key structural components.

Cellulose: The most abundant organic polymer, forming the cell walls of plants. Its beta-glycosidic linkages are indigestible by humans, acting as dietary fiber.
Chitin: A structural polysaccharide found in the exoskeletons of arthropods and fungal cell walls, offering strength and protection.

Cellular Communication and Recognition

Polysaccharides can combine with proteins or lipids to form glycoconjugates (glycoproteins and glycolipids) on cell surfaces. These molecules are crucial for cell signaling, adhesion, and immune recognition. Heparin is an example of a heteropolysaccharide that acts as an anticoagulant.

Comparison of Key Polysaccharides


Feature	Starch	Glycogen	Cellulose	Chitin
Function	Energy storage in plants	Energy storage in animals	Structural support in plants	Structural support in arthropods/fungi
Monomer	α-glucose	α-glucose	β-glucose	N-acetylglucosamine
Structure	Linear and branched	Highly branched	Linear	Linear
Solubility	Partially soluble	Insoluble	Insoluble	Insoluble
Digestibility	Easily digested by humans	Easily converted to glucose in animals	Indigestible by most animals	Indigestible by most animals

How are polysaccharides used?

Beyond their biological roles, polysaccharides have extensive industrial applications.

Food Industry

They function as thickeners, gelling agents, and stabilizers. Examples include pectin (in jams), carrageenan (in dairy products), and inulin (as a prebiotic fiber).

Biomedical and Pharmaceutical Applications

Polysaccharides are used as biocompatible and biodegradable biomaterials. They are utilized in drug delivery systems, some vaccines, and tissue engineering scaffolds.

Industrial and Textile Uses

Cellulose is key for paper and textiles. Dextrins from starch are used in adhesives, and alginate is used in wound dressings.

Water Treatment

Polysaccharides aid in wastewater filtration and purification, with bacterial polysaccharides helping in flocculation.

Conclusion

Polysaccharides are vital and versatile macromolecules serving essential roles in all life, from energy storage and structural support to cellular communication. Their diverse structures enable a wide array of applications in food, medicine, and industry. As safe, economical, and renewable resources, polysaccharides continue to be a focus of research for future innovations.

For additional insights into the structural diversity of polysaccharides and their biological significance, consider exploring the resources provided by the National Center for Biotechnology Information (NCBI).

Frequently Asked Questions

The primary difference lies in the type of glycosidic bond linking the glucose monomers. Starch uses alpha-glycosidic bonds, which humans can digest, while cellulose uses beta-glycosidic bonds, which are indigestible for humans and form strong fibers.

Polysaccharides are considered complex carbohydrates. They are large polymers, unlike simple carbohydrates (monosaccharides and disaccharides), which are composed of one or two sugar units, respectively.

Plants store excess glucose as starch in their roots, seeds, and fruits, which they can later break down for energy. Animals store glucose as glycogen, primarily in the liver and muscles, and can quickly mobilize it for energy.

No. While humans can digest storage polysaccharides like starch, they lack the necessary enzymes (like cellulase) to break down structural polysaccharides such as cellulose and chitin. These indigestible polysaccharides function as dietary fiber.

Chitin is a structural polysaccharide that provides strong, protective support. It is the main component of the exoskeletons of insects and crustaceans and is also found in the cell walls of fungi.

Polysaccharides like chitosan and dextran are used in drug delivery systems as nanoparticles. Others are used to create hydrogels for wound management and scaffolds for tissue engineering due to their biocompatibility.

Heteropolysaccharides are made from multiple types of monosaccharides. Examples include heparin, used as an anticoagulant, and hyaluronic acid, a component of connective tissues and skin.