Table of Contents
What is Polysaccharide?
Polysaccharide are chains of carbohydrate that are connected to each other by glycosidic bond and consist of repeating carbohydrate to form a long chain. The term polysaccharide can be broken into words, where poly means many and saccharide means various sugars.
Thus, it means a group of various sugars consisting around 10 moieties. These carbohydrate moieties, are the biomolecules which are made up carbon, hydrogen and oxygen. Carbohydrates can be categorized in two; simple and complex.
Carbohydrates forms the structure and are the energy source. Carbohydrates that can be easily broken down, to provide energy are termed as simple carbohydrate, whereas those that require time to be broken down, however does not interfere with the increment of sugar level and are fibrous in nature are called as complex carbohydrates.
Example of simple carbohydrate are glucose and that of complex carbohydrate are chitin, glycogen and cellulose.
a) The formula for polysaccharide are Cx (H2O) y.
b) The ration of carbon to hydrogen to oxygen is 1:2:1.
c) Polysaccharide do not dissolute in water.
d) They are less active and are present in condensed form.
e) In taste they aren’t pleasing.
f) They cannot form crystals
g) They are white in color on isolation.
The polysaccharide can be heterogenous and its structure will be branched or linear depending on the polysaccharide it forms. On the basis of sugar molecules, oligosaccharide and disaccharide differ from polysaccharide, where 2 sugar molecules are the disaccharide and more than that sugar moieties are called as oligosaccharide, however they aren’t huge like the polysaccharides.
Polysaccharide Dehydration Synthesis
Dehydration means water is been worn out of a molecule, in polysaccharide it happens when to a sugar molecule another molecule gets attached and results in the expulsion of water molecule. Another way for synthesis to occur is when the sugar molecule attach to the other molecule, they are in a condensed form and water is expelled.
Hydrolysis is the exact reversion of condensation, where a water molecule is lost. In hydrolysis water molecule gets used. To form a monosaccharide from polysaccharide it is known as saccharification. Enzymes such as maltase, pancreatic and salivary amylase break down the sugar molecule, such as the enzyme acting on starch is salivary amylase, resulting in the formation of maltose.
In the small intestine, further the digestion of carbohydrate will take place. In the small intestine, when the partly digested sugar molecule reach, pancreatic juice is released by the pancreas, which will further degrade them into small sugars.
There are enzymes present on the borders of intestine, which will take up the simple sugars with the use of transporters and through the passive transport will reach the capillaries and will be moved to organs such as liver, where it will serve as reserves for glycogen or it could also synthesize ATP.
The enzymes are found on the border of intestine are sucrase, lactase, maltase and isomaltase. These polysaccharide will be attacked at the 1-6 linkage and will form maltose, which will further be cleaved by the enzyme maltase forming glucose, explicitly two molecules.
If instead sucrose or lactose would be present then the respective enzyme sucrase and lactase would act on it. Only those sugar molecules which reach the large intestine, which cannot be absorbed and will be colonized by the microflora in the intestine anaerobically and release gases and fatty acid which are utilized by the body and the gases are released when we fart.
From glucose the formation of glycogen is known as the glycogenesis, which would occur when there is huge amount of glucose in the liver and the muscles. Large glucose chains are formed from small glucose molecule, and in the glycogenesis process from those sugar molecules which are present in the cell, glycogen is formed. These molecules when have to be utilized are again broken into glucose by the glycogenesis process.
The metabolization of glycogen is known as glycogenolysis. From the glycogenolysis process, glucose is formed, where from the glycogen a glucose molecule is cleaved and forms glucose-1-phosphate and then again forms glucose-6-phosphate to proceed with the glycolysis. Glycogenolysis takes place in the liver.
The attachment or linkage of a protein, organic molecule or a biomolecule to the glycan is known as glycosylation. For example, in O linked glycosylation, the O glycan is linked to the oxygen of amino acid such as tyrosine, threonine and etc.
Another example is N linked glycosylation where the N glycan is linked to nitrogen atom of another amino acid which is asparagine. There are various example such as Sulphur linked glycan, Phosphorous linked glycan, Carbon linked glycan and others.
When the polysaccharide is formed from a single type of sugar it is called as Homopolysaccharide. Heteropolysaccharide is made up of various sugar molecules. These are two types of polysaccharide classification on the basis of the type of sugar present.
There are two types of polysaccharide and they are Storage polysaccharide and Structural polysaccharide. On the basis of their name is their function.
Structural polysaccharide are like chitin, cellulose which forms the structure of a certain animal. Example is to make the exoskeleton of animals, chitin is required.
Storage polysaccharide are those stress various sugar molecules serving as the reserves. For example, the storage of glycogen in animals in its simple form.
There are various polysaccharide such as cellulose which is made up of glucose molecules chains in a linear array. Another polysaccharide is glycogen which is formed in liver and muscle and comprises of glucose in a branched chain and is a storage polysaccharide in animals.
Another polysaccharide is Starch which connects glucose moiety to each other by glycosidic bond. A polysaccharide with nitrogen is the chitin, which is a structural polysaccharide that forms structure in various organism. Other example are Zylan, fucoidan, arabinoxylan, galactomannan and others.
Biological Importance of Polysaccharide
The major energy source is the carbohydrates, which are taken up by animals to produce ATP. Example using the substrate level phosphorylation, from glucose ATP is produced. However excess amount of glucose can result in diabetes and similarly excess of fructose can could result improper absorption from small intestine.
Thus, to prevent that fructose is relocated to large intestine where it will be colonized by the micro-flora. In plants, they function as storage polysaccharide, such as storage of glucose in the starch form, which will used by plants to prepare food.
Glycogen is stored in animals, where it can be broken into glucose to meet the energy requirements. In animals, they also form the skeleton and covering of various organism and have industrial applications as well.
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