Polysaccharides! A big word for big molecules! We’ll explain soon.
In a nutshell, polysaccharides are complex carbohydrates that are molecules consisting of long chains of monosaccharide units. (Poly vs mono, get it?)
They greatly vary in terms of structure and function, but almost all living beings on earth use them. For example, polysaccharides such as starch in plants and glycogen in animals are responsible for storing energy and keeping it ready to meet our metabolic needs.
Cellulose, a polysaccharide found in plants, provides structural integrity and support. Chitin, found in insects and crustaceans, is responsible for the hard exoskeleton that provides structure and protection.
In this blog post, we’ll look more closely at these crucial compounds in our bodies, learn about what they do, and check out their other applications.
Understanding Polysaccharides
To understand polysaccharides, we must first understand monosaccharides, which they are made out of.
Monosaccharides are water-soluble simple carbohydrates that consist of single sugar molecules that cannot be hydrolyzed to give a simpler sugar. They are the basic unit from which all other carbohydrates are built.
Most monosaccharides have the formula (CH2O)x, though not all molecules with this formula are monosaccharides. Common monosaccharides include glucose (dextrose), fructose (levulose), and galactose.
Disaccharides, also called double sugars, are when two monosaccharides are linked. Some common examples are lactose, maltose, and sucrose.
Next, we have oligosaccharides, which are three to six monosaccharides that are linked. Common examples are raffinose, galactose, and melibiose.
Finally, we have the biggest ones of them all – polysaccharides! These are long chains of monosaccharides all linked. Polysaccharides are complex biomolecules that play crucial functions in nature like storing energy in humans and animals and giving structure to plants. Examples of polysaccharides include starch, glycogen, cellulose, and chitin.
Types of Polysaccharides
Polysaccharides can broadly be categorized as structural or storage.
Structural Polysaccharides
Cellulose – The main role of cellulose is to provide plants with structural support. It is water-insoluble and forms a fibrous network that envelopes plant cells and helps them maintain their shape. Cellulose is crucial for a plant’s growth and stability, allowing it to keep upright and reach for the sun.
Cellulose can also be used in commercial applications. For example, cotton fibers are almost pure cellulose, making them extremely durable and suitable for textiles.
Chitin – Chitin is the main structural component in the exoskeletons of arthropods such as crustaceans, insects, and arachnids (spiders). It provides these little creatures with a strong outer exterior that protects them from physical damage.
In addition to exoskeletons, chitin is also found in the cell walls of fungi, where it provides structural support.
Storage Polysaccharides
Starch and glycogen are the two most common storage polysaccharides, and they are both glucose units that store energy for plants and animals.
Starch – A plant polysaccharide that usually has two types of molecules: amylose and amylopectin. Starch is how plants store their energy. For example, potatoes and other root veggies store them in the tubers, and rice, wheat, and corn store them in the seeds.
When the plants require energy, starch is broken down into glucose molecules, which are then used.
Glycogen – Glycogen is an animal polysaccharide with extensive branching, allowing for the rapid release of glucose when energy is needed. It can be found in animals, bacteria, and fungi, and it is the primary way OUR body stores energy.
We store glycogen in our liver and muscles. The liver acts as glucose storage to maintain our blood sugar levels, while the muscles provide a quick increase of energy during physical activity.
Functions of Polysaccharides
As mentioned earlier, structural polysaccharides like cellulose and chitin provide support to plants and other organisms. Storage polysaccharides like starch and glycogen provide animals and plants with a way to store energy in the form of glucose.
In addition, polysaccharides are complex carbohydrates that are crucial for your digestive process. Dietary fiber is made up of some polysaccharides that we cannot digest, such as cellulose, pectins, and some resistant starches.
These fibers have numerous health benefits, including promoting better bowel movements, preventing constipation, promoting gut health, and lowering cholesterol.
Dietary fiber is found in many types of foods, but the most commonly known are fruits, vegetables, whole grains, legumes, nuts, and seeds. It has long been known that a diet rich in fiber is a healthy one!
Industrial and Medical Applications of Polysaccharides
As mentioned earlier, cellulose is water-insoluble and can be used in many applications, such as the paper, medical, and textile industries. It can also be widely used in medical applications such as wound dressing and blood purification.
Another polysaccharide that is widely used in medicine is chitin, which is an absorbable suture material with a high tensile strength.
Lastly, dextran, a complex polysaccharide, is often used as a blood plasma substitute in situations where a blood transfusion isn’t an option. Dextran is water-soluble and compatible with the body’s natural fluids, making it ideal for plasma substitution.
Conclusion
Polysaccharides are complex carbohydrates made up of simple sugar compounds called monosaccharides. Glycogen and starch are responsible for storing energy in plants and animals, while cellulose and chitin help plants and arthropods with structure and protection.
Polysaccharides contribute to your levels of dietary fiber, which is crucial for good health. Fiber can be found in many food groups but some of the more common ones are veggies, fruits, seeds, whole grains, and nuts.
There are also industrial applications of polysaccharides, like using chitin as dissolvable sutures or dextran as a blood plasma substitute.
Polysaccharide FAQs
What is the difference between a polysaccharide and a monosaccharide?
A monosaccharide is the simplest form of carbohydrates, consisting of a single sugar molecule that cannot be further hydrolyzed into simpler sugars. Polysaccharides are complex carbohydrates with glycosidic linkages made up of numerous long chains of monosaccharide units.
While monosaccharides serve as building blocks and immediate energy sources, polysaccharides function as energy storage forms (like starch and glycogen) and structural components (such as cellulose and chitin) in living organisms.
How do polysaccharides function in the human body?
In the human body, polysaccharides such as glycogen serve as energy storage, quickly metabolizing glucose, a type of monosaccharide, for immediate energy. In addition, the polysaccharides that form dietary fiber help with digestion, regulate blood sugar levels, and contribute to maintaining a healthy gut.
Can humans digest all types of polysaccharides?
No, humans cannot digest all types of polysaccharides. While we can digest polysaccharides like starch and glycogen, breaking them down into glucose for energy, we lack the necessary enzymes to break down certain structural polysaccharides like cellulose found in plant cell walls.
These indigestible polysaccharides are what make up dietary fiber that will pass through the gastrointestinal tract largely unchanged. Dietary fiber helps improve gut health, facilitates better bowel movements, helps control blood sugar, and improves overall well-being.
What are some common sources of polysaccharides in our diet?
Common sources of polysaccharides in our diet include starchy foods like potatoes and rice, legumes, vegetables, nuts, seeds, and whole grains.