Polysaccharide is formed by condensation and dehydration of multiple monosaccharide molecules, and it is a kind of carbohydrate with complex and huge molecular mechanism. Polysaccharide polysaccharide All carbohydrates and their derivatives that conform to the concept of polymer compounds are called polysaccharides. There are glucose, mannan, galactan, etc., which are composed of one type of monosaccharide (usually the suffix an is added to the English monosaccharide stem), hetero polysaccharide, which is composed of two or more monosaccharides, glucosamine dextran containing amino sugar, etc., and their chemical structures are really diverse. As far as molecular weight is concerned, there are polysaccharides from 0.5 million molecules to more than 106. A polysaccharide is a polymerized sugar composed of at least more than 10 monosaccharides with glycosidic bonds. Short chains with less than 10 are called oligosaccharides. However, as far as the sugar chain is concerned, even if an oligosaccharide combines protein and lipid, as far as the whole molecule is concerned, if it belongs to a polymer, it also belongs to a polysaccharide in a broad sense, so it is specially called a complex poly－saccharide or a complex carbohydrate (glycoprotein, glycolipid, proteoglycan). The biological function of polysaccharide usually has the function of storing biological energy (such as starch, glycogen and inulin) and supporting structure (such as cellulose, chitin and mucopolysaccharide). However, the polysaccharide components of cell membrane and cell wall are not only supporting substances, but also directly participate in the process of cell division, and in many cases become the active sites of mutual recognition structures such as cells and cells, cells and viruses, cells and antibodies. Biosynthesis is usually carried out by transglycosylase bound to cell membrane cytoplasm (Golgi apparatus, plasma membrane, rough endoplasmic reticulum, etc.). Various glycosides are used as precursors. In the biosynthesis of bacterial cell walls and polysaccharides, polyterpenoid alcohol derivatives (especially those called bacterial terpenoids) take part in the reaction as intermediates, and there are similar reports on the synthesis of some polysaccharides in animals and plants. On the other hand, in the process of decomposition, there are many glycosidases that are specific to the sugar arrangement order and bond properties of sugar chains. In animal cells, enzymes of lysosomal system mostly exist. In addition, we can often see genetic diseases caused by the defect of one of these enzymes. This is a typical example showing the importance of polysaccharide metabolism.

chemical property

Polysaccharide has no sweetness, can not form a true solution in water, but can only form a colloid, which has no reducibility and no rotation, but has optical rotation.

classify

Homogeneous polysaccharide: a polysaccharide condensed from a monosaccharide molecule, called homogeneous polysaccharide. Common ones are: starch, glycogen, cellulose and so on.

Heterogeneous polysaccharide: a polysaccharide condensed from different monosaccharide molecules, called heterogeneous polysaccharide. Common ones are hyaluronic acid, chondroitin sulfate and so on.

biological function

Some polysaccharides, such as cellulose and chitin, can form plant or animal skeletons. Polysaccharides such as starch and glycogen can be used as energy storage materials for organisms. Heterogeneous polysaccharides form proteoglycans with protein through valence bonds, which play biological functions, such as being used as body lubricant, recognizing cells of foreign tissues, and basic components of blood group substances.

Polysaccharide compounds are widely found in animal cell membranes and cell walls of plants and microorganisms. They are high molecular polymers connected by aldehyde groups and ketone groups through glycoside bonds, and they are also one of the four basic substances that constitute life.

In 1950s, it was found that fungal polysaccharide had anticancer effect, and later it was found that lichen, pollen and many plants all contained polysaccharide compounds, which were separated and purified, and their chemical structure, physical and chemical properties and pharmacological effects were determined, especially the anti-tumor and immune enhancement effects of polysaccharide compounds were deeply studied.