There are four main classes of complex bioorganic substances: proteins, fats, nucleic acids and carbohydrates. Polysaccharides belong to the latter group. Despite the "sweet" name, most of them perform completely non-culinary functions.
Polysaccharide - what is it?
The substances of the group are also called glycans. A polysaccharide is a complex polymer molecule. It is composed of individual monomers - monosaccharide residues, which are combined using a glycosidic bond. Simply put, a polysaccharide is a molecule built from the combined residues of simpler carbohydrates. The number of monomers in a polysaccharide can vary from a few dozen to a hundred or more. The structure of polysaccharides can be either linear or branched.
Physical properties
Most polysaccharides are insoluble or poorly soluble in water. Most often they are colorless or yellowish. Most polysaccharides are odorless and tasteless, but sometimes it can be sweetish.
Basic chemical properties
Hydrolysis and derivatization can be distinguished among the special chemical properties of polysaccharides.
Hydrolysis is a process that occurs during the interactioncarbohydrate with water with the participation of enzymes or catalysts such as acids. During this reaction, the polysaccharide breaks down into monosaccharides. Thus, we can say that hydrolysis is the reverse process of polymerization
Starch glycolysis can be expressed by the following equation:
(S6N10O5) + n N2O=n C6N12O 6
So, when starch reacts with water under the action of catalysts, we get glucose. The number of its molecules will be equal to the number of monomers that formed the starch molecule.
The formation of derivatives can occur in the reactions of polysaccharides with acids. In this case, carbohydrates attach acid residues to themselves, resulting in the formation of sulfates, acetates, phosphates, etc. In addition, attachment of methanol residues can occur, which leads to the formation of esters
Biological role
Polysaccharides in the cell and the body can perform the following functions:
- protective;
- structural;
- reserve;
- energy.
The protective function lies primarily in the fact that the cell walls of living organisms are composed of polysaccharides. So, the cell wall of plants consists of cellulose, fungi - of chitin, bacteria - of murein.
In addition, the protective function of polysaccharides in the human body is expressed in the fact that glands secrete secretions enriched with these carbohydrates, which protect the walls of such organs asstomach, intestines, esophagus, bronchi, etc. from mechanical damage and penetration of pathogenic bacteria.
The structural function of polysaccharides in the cell is that they are part of the plasma membrane. They are also components of organelle membranes.
The next function is that the main reserve substances of organisms are precisely polysaccharides. For animals and fungi, this is glycogen. Starch is the storage polysaccharide in plants.
The last function is expressed in the fact that the polysaccharide is an important source of energy for the cell. A cell can get it from such a carbohydrate by splitting it into monosaccharides and further oxidizing it to carbon dioxide and water. On average, when one gram of polysaccharides is broken down, a cell receives 17.6 kJ of energy.
Use of polysaccharides
These substances are widely used in industry and medicine. Most of them are obtained in laboratories by polymerization of simple carbohydrates.
The most widely used polysaccharides are starch, cellulose, dextrin, agar-agar.
| Name of substance | Use | Source |
| Starch | Finds application in the food industry. It also serves as a raw material for the production of glucose, alcohol. It is used for the manufacture of glue, plastics. Also used in the textile industry | Derived from potato tubers, as well as seeds of corn, rice chaff, wheat and other starch-rich plants |
| Pulp | Used in the pulp and paper and textile industries: cardboard, paper, viscose are made from it. Cellulose derivatives (nitro-, methyl-, cellulose acetate, etc.) are widely used in the chemical industry. They also produce synthetic fibers and fabrics, artificial leather, paints, varnishes, plastics, explosives and much more | This substance is obtained from wood, mainly coniferous plants. It is also possible to obtain pulp from hemp and cotton |
| Dextrin | Is a food additive E1400. Also used in the manufacture of adhesives | Produced from starch by heat treatment |
| Agar-agar | This substance and its derivatives are used as stabilizers in the manufacture of food products (for example, ice cream and marmalade), varnishes, paints | Extracted from brown algae, as it is one of the components of their cell wall |
Now you know what polysaccharides are, what they are used for, what their role in the body is, what physical and chemical properties they have.
