carbohydrates and its example , Sources , Classification , types of carbohydrates ,and functions of carbohydrates etc.
What are carbohydrates ?
Carbohydrate are primary produced by plants and form a very large group of naturally occurring organic compounds. Some common examples are Cane sugar ,glucose , starch etc. Most of them have general formula Cx(and were considered as hydrates of carbon from where the name carbohydrate was derived .
All simple sugars contain potential aldehyde or Ketone group Play . All compound which are made up of simple sugars also contain the potential aldehyde Ketone group . These groups may be in the free form o r in the combined form. These two groups are associated with reducing properties of sugars .
Classification of Carbohydrates
• Monosaccharides
They contain only one molecule of sugar. They cannot be hydrolysed into father into simpler molecules the ratio of carbon hydrogen and oxygen in monosaccharides is 1 is to 2 is to 1. The names of the most in the monosaccharides end with ose .
Examples : Glucose, fructose, mannose etc. Depending on the number of carbon atoms present they are called as dioses, trioses, tetroses, pentoses and hexoses.
• Disaccharides
These are sugars containing two molecules of monosaccharides. The union occurs between the first carbon of monosaccharide and second or fourth carbon of second monosaccharide .If the linkage occurs between the reducing group (aldehyde or ketone group ) of both monosaccharides the reducing property is lost. The resulting compound in a non reducing sugar that is sucrose. It does not form osazones .
If the linkage involves the aldehyde or Ketone group of only one of the monosaccharides the aldehyde are Ketone group of other monosaccharide permits reduction. The resulting compound is reducing sugar eg. lactose and maltose. They can form osazones. Disaccharides have the general formula( C12 H22 O11 ).
Sucrose :
It is the commonly called as tables sugar. Also it is called as Cane sugar since it is obtained from sugarcane. It is composed of one molecule of glucose and one molecule of fructose. Linkage involves the aldehyde group of glucose and Ketone group of fructose. So these two reducing groups are not available for reduction. So sucrose is a non- reducing sugar.
Before hydrolysis Sucrose is dextrorotatory on hydrolysis sucrose gives one molecule of glucose and one molecule of fructose. Fructose is strongly laevorotatory than glucose which is the dextrorotatory . Live rotation induced by the presence of fructose is called inversion the product of hydrolysis which contains both glucose and fructose is called invertsugar .
Maltose :
It is composed of two molecules of glucose. Linkage occurs between C1 of one glucose molecule and C4 of the Other glucose molecule. Show the aldehyde group of second glucose molecule is free and available for reduction. Maltose is a reducing sugar. It can form osazone with phenylhydrazine. Germinating cereals and malt are the Natural sources of maltose. Maltose is the intermediate product in The breakdown of starch by the enzyme the amylase in the intestinal tract .
Lactose :
It is present in milk. So it is commonly called as milk sugar. It contains one molecule of galactose and one molecule of glucose. The linkage occurs between C1 of galactose and C4 of glucose. So the aldehyde group of glucose is free and it is available for reduction. Lactose is a reducing sugar. So it can form osazones.
• Oliogosaccharides
They yield 2 to 10 molecules of monosaccharides on hydrolysis. Depending on the number of monosaccharides units present they are called trisaccharide and tetrasaccharide etc. They can have reducing property if they contain free aldehyde or ketone group not involving the linkage. The reducing property decreases as the number of of carbohydrate units increases. Antibodies and coagulation factors contain oligosaccharide units .
• Polysaccharides
They yield more than 10 molecules of monosaccharides on hydrolysis . They can be considered as condensation products of several monosaccharide units joined together by glycosidic linkage. They have high molecular weight and are colloidal in nature. Polysaccharides are classified as :
• Homopolysaccharides :- if they yield one type of monosaccharide on hydrolysis that is starch, glycogen ,cellulose .
• heteropolysaccharides :- if they ILD more than one type of monosaccharide on hydrolysis eg. Heparin and hyaluronic acid.
STARCH :- Starch is a homopolysaccharide containing several units of glucose. It is a storage form of carbohydrate of plants. It is found abundantly in roots ,tubers, vegetables, fruits and cereals. In these sources, starch occur in the form of granules. Starch granules contain two types of polymeric units of glucose called amylose and amylopectin .
Amylose is a straight chain polymer. It contains glucose unit linked by Alpha -1-4 glycosidic linkage. It gives blue colour with dilute iodine solution.
Amylopectin is a branched chain polymer. The glucose units are linked by Alpha 1-4 glycosidic linkage in the straight chain like amylose. But at points of branching it is alpha 1 -6 glycosidic linkage. Amylopectin gives a reddish violet colour with iodine solution .
GLYCOGEN :- it is a storage form of carbohydrate in animals so it is called as animal starch. It occurs in in animal tissues especially in liver and muscles. It is also present in yeast and fungi which do not have chlorophyll system. The molecular weight of glycogen is very high and it is about 5,000,000.
Glycogen is a polymer of glucose. In the straight chain the glycosidic linkage is 1-4 whereas at branch points it is 1-6. A branch point occurs for every 12 to 18 glucose units.
CELLULOSE :- It is a structural polysaccharide .It is found in fibrous parts of plants. It consists of long unbranched chain of Beta D - glucose molecules United by 1-4 linkage.
Cellulose is not sweet in taste. Also it does not give colour with Iodine. It is insoluble and resistant to hydrolysis. Because of its inert nature It is not digested in in the intestine. So it increases the bulk of fecal matter. The bulk increases the peristalsis and helps in defecation .
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