Importance of Polysaccharides (Starch, Cellulose, Glycogen)

Polysaccharides are carbohydrates with highly branched structures that are complex. This complex polysaccharide is composed of repeating units of monosaccharides joined together by glycosidic linkages, and the importance of polysaccharides needs to be learnt in detail. A numerical representation of the number of sugar molecules that combine to form more giant molecules is represented by the letter n. Glycans are another term for polysaccharides. Homopolysaccharides and heteropolysaccharides are the two main categories of polysaccharides. In nature, three primary polysaccharides are found: starch, cellulose, and glycogen. All three have applications in everyday life.

Polysaccharide

Polysaccharides are monosaccharide chains joined together by glycosidic bonds or linkages to produce a linear or branching structure. As a result, polysaccharides are polymers made up of monosaccharide molecules. 

Molecular structure of polysaccharide 

Glycosidic linkages, which attach monosaccharides to each other, are the fundamental method by which all polysaccharides are created. These glycosidic linkages are formed by an oxygen molecule forming a link between two carbon rings. The bond is created when a hydroxyl group is removed from the carbon of one molecule, and a hydrogen atom is removed from the hydroxyl group of another monosaccharide, resulting in the formation of the bond. The reaction is classified as a dehydration reaction since it results in the expulsion of two hydrogen molecules and one oxygen molecule. The structure of the mixed molecules dictates the structures and qualities of the polysaccharide formed as a result of the combination. In contrast, a polysaccharide used for support is often a lengthy chain of monosaccharides that create fibrous structures, but a polysaccharide used for energy storage will provide simple access to the constituent monosaccharides.

Starch

It is present in all photosynthetic plants, and it is typically found in the roots and seeds of the plants. Starch is a carbohydrate found in the roots and seeds of plants. All plants manufacture glucose, and any excess glucose is stored in the form of starch. Granules of glucose were discovered in the seeds of plants. It is possible to obtain a colloidal suspension by heating the granules in the presence of water. Amylopectin and amylose are the two components produced due to this procedure. Because it is made entirely of glucose molecules that have been bonded together, it is referred to as glucan.

• In amylose, the –D– glucose subunits are joined by –1,4 glycosidic linkages, resulting in an unbranched polymer structure.
• Amylopectin is the portion of starch that is branched, and it is composed of –D– glucose subunits joined together by a –1,6 glycosidic bond.

Cellulose

Cellulose is a critical structural component of the cell wall of all photosynthetic plants, including algae. It has a fibrous texture and is very insoluble in water. The compound D-glucose is also known as alginate and is created by combining D-glucose units. A beta linkage connects these units, in contrast to the glycogen and starch that connects them in the first place. In this way, the polysaccharides are constrained to a straight-chain shape, rather than a helical structure. The hydroxyl groups on the exterior of this chain arrangement are pointing away from the chain. The hydrogen bonding between the two hydroxyls causes the two chains to stack on top of each other when they are close together.

Glycogen

It is just the D-glucose units that are used to construct glycogen. As glucan, it is a carbohydrate only available to plants and animals when they need it most. Its structure is comparable to that of amylopectin, with one exception: it is heavily branched instead of amylopectin. Branching occurs more often in this molecule, with branches appearing around every six glucose units. As a result, it acts in a manner distinct from that of amylopectin. Due to its enormous molecular weight and non-compact nature, it is not suitable for small spaces. In plants and animals, it performs a variety of crucial roles because of its distinct structural and formation characteristics. It serves as a glucose reserve for the cells in our body. It cannot diffuse away from the cell membrane because of its compact structure.

Features of polysaccharide

• Non-sugars, or glycans, are the most popular term for polysaccharides.
• Biomolecules with enormous molecular weights are known as polysaccharides.
• Several of them are unable to dissolve in water.
• It’s not uncommon for polysaccharides to taste bland.
• They turn into an amorphous powder after they have been dried out.
• There are many different types of polysaccharides, all of which are bound together by covalent links known as glycosidic linkages.
• It is possible for the carbon atom at the end of a polysaccharide to be reduced or non-reduced (terminal atom involved in the glycosidic bond)
• As a rule of thumb, polysaccharides have a formula of (C6H10O5)n, with n ranging from 100 to 2500.

Conclusion

Polysaccharides are polymers of simple sugars bound together by glycosidic linkages found in plants and animals. Because they are polymers with a large molecular weight, they are considered real macromolecules. Polysaccharides are classified into two categories: homopolysaccharides (which include just one type of monomeric unit) and heteropolysaccharides (which contain more than one type of monomeric unit). Polysaccharides can be divided into two categories based on their function: structural polysaccharides and storage polysaccharides. Storage polysaccharides serve as a reserve food source, but structural polysaccharides are responsible for most of the structural components of organisms, such as cell walls, fibrous tissue, and the exoskeleton. Starch and glycogen are the polysaccharides that serve as storage for plants and animals, respectively. Cellulose is the most abundant structural polysaccharide in plants, and it is responsible for the production of wood, paper, and cotton. In animals, chitin is an example of a structural polysaccharide that serves a structural function.