Carbohydrates in living organisms are used as the main source of energy. Carbohydrates are formed as a result of photosynthesis by storing solar energy in chemical bonds. Some carbohydrates are involved in the formation of nucleic acids . acids and other components. Also make up some of the constituent parts of the cell, for example, the cell walls of some plants consist of cellulose.
Carbohydrates are divided into three types according to the number of monomers - monosaccharides, disaccharides and polysaccharides.
Monosaccharides
Monosaccharides, as well as oligosaccharides or simple carbohydrates. Cannot be broken down by hydrolysis into simpler molecules sugar, from where they got their name. As a rule, monosaccharides contain from three to eight carbon atoms. The most important from the point of view of biology are molecules of five and six carbon atoms, pentose and hexose, respectively.
Representatives of pentose, ribose and its derivative, deoxyribose, form genetic molecules: ribonucleic acid (RNA) and deoxyribonucleic acid (DNA). Glucose and fructose are the most important molecules of the six carbon atoms. Glucose is the main component of di- and polysaccharides, is produced during photosynthesis and serves as the main "fuel" for both plants and animals. Fructose is found in fruits and corn syrup.
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Disaccharides
Disaccharides are molecules consisting of two monosaccharides connected by a glycoside bond. Disaccharides are used for the most part, plants as food for a short period of time. The most popular molecules disaccharides: sucrose, lactose (found in milk and dairy products) and maltose (malt sugar). Sucrose is the usual table sugar to which we are accustomed, consists of glucose and fructose molecules, mainly found in cane sugar and beets. Lactose consists of glucose and galactose. Maltose consists of two glucose molecules, it is contained in malt, and is also released during the digestion of starch.
Disaccharides are synthesized by dehydration. Energy production from disaccharide is produced by hydrolysis, that is by adding a water molecule.
Polysaccharides
In nature, most carbohydrates are presented in the form of polysaccharides, consisting, as a rule, of glucose. The main polysaccharide in nutrition is starch. Starch molecules can contain up to half a million glucose monomers in a branched form. Starch is mainly contained in products such as potatoes, rice, corn and wheat. In the process of digestion, the body starches are broken down into di- and monosaccharides.
Glycogen is the most common form of glucose preservation in animals. Glycogen molecules are more branched than starch molecules. In vertebrates, it is produced in the liver, stored also in the liver and in the muscles.The most important polysaccharide is cellulose. Cellulose is considered the most common polysaccharide in nature. Cellulose consists of many glucose chains arranged one after the other and connected by a hydrogen bond. Together they form a stable array, organizing the fiber.
In animals, the most common polysaccharide is chitin. Chitin makes up the exoskeleton of insects, crabs and spiders. Also, the cell walls of many fungi consist of chitin. Chitin has a similar structure to cellulose, but there is an amino group in chitin.
