[Biology Class Notes] on Polysaccharides Pdf for Exam

• Polysaccharide is a long chain of carbohydrates whose molecules consist of numerous sugar molecules bonded together by glycosidic linkages. Polysaccharide examples: Starch, Cellulose or Glycogen are polysaccharides Carbohydrates. As we know carbohydrates are a major source of food and necessary for getting energy for the survival of living organisms. Consisting of Carbon, Hydrogen and Oxygen atoms, carbohydrates are made up of two basic compounds, namely aldehydes and ketones.

• Monosaccharide Examples: Glucose and Galactose

• Disaccharide Examples: Sucrose and Maltose

• Polysaccharide Examples: Starch, Glycogen and Cellulose

• Polysaccharides are an important class of biological polymers and generally contain more than 10 monosaccharide units, however, oligosaccharides are polysaccharides with three to 10 monosaccharide units. Biological polysaccharides help in performing various functions in living organisms, either structural functions or energy storage functions. Two examples of structural polysaccharides include cellulose and chitin; the cell walls of plants and other organisms are composed of cellulose which is considered the most abundant organic molecule on Earth. 

• Polysaccharide Meaning: Poly means ‘many’ and saccharide means ‘sugar’; so a polysaccharide contains many sugar molecules.

See the below polysaccharide structure for a clearer understanding.

 

 

Types of Polysaccharides

Heteropolysaccharides and Homopolysaccharides are the two types of polysaccharides that are described in the following:

• When more than one kind of monosaccharide is present in the polysaccharide structure, it is known as heteropolysaccharide or heteroglycan. In contrast, homopolysaccharide or homoglycan is the kind of polysaccharide that has the same type of monosaccharides. 

• Examples of homopolysaccharides are glycogen, cellulose, starch and insulin. Glycogen is made up of a large chain of molecules and is found in animals and fungi. Cellulose is present in the cell wall of the plants and comprises long chains of beta glycosides. Starch is produced by the condensation of amylopectin and amylose; available largely in plants, fruits, seeds, etc. Insulin is composed of numerous fructofuranose molecules linked together in chains, it is found in tubers of artichoke, dahlia, etc.

• Examples of heteropolysaccharides are hyaluronic acid, heparin, chondroitin-4-sulfate and gamma globulin. Hyaluronic acid is made up of N-acetyl-glucosamine and is found in connective tissues and skin. Heparin is made up of D-glucuronic acid, N-sulfo-D-glucosamine and L-iduronic acid and it is largely distributed in blood and mast cells. Chondroitin-4-sulfate sugars are D-glucuronic acid and N-acetyl-D-galactosamine-4-O-sulfate. It is found in the cartilages. Gamma globulin is composed of N-acetyl-hexosamine, D-galactose and D-mannose as the component sugars of the polysaccharide and is present in the blood.
   

Characteristics of Polysaccharides

1. Many of the polysaccharides are insoluble in water.

2. These are not sweet.

3. These are hydrophobic.

4. These do not form crystals on desiccation.

5. Polysaccharides can be extracted in the form of a white powder.

6. These have a high molecular weight as carbohydrates.

7. These are compact and osmotically active inside the cells.

8. The hydrogen to oxygen ratio in them is 2:1 and they consist of hydrogen, carbon and oxygen. 

 

Functions of Polysaccharides

1. Structural Functions- Common sources of energy are nutrition polysaccharides and most of the organisms can easily break down starch into glucose. However, some complex polysaccharides are not very digestible that are known as dietary fibre and these provide important elements in the diet for humans. There are soluble fibre and insoluble fibre that are associated with various functions in the body. The former is responsible for lowering cholesterol levels (bad) in the blood, normalizing blood lipid levels and reducing sugar response after eating. The latter or insoluble fibre reduces the risk of diabetes.

2. Storage Functions- Storage polysaccharides are starch, glycogen and insulin. A glucose polymer that is insoluble in water is Starch. Both humans and animals have amylases to digest starches easily. Starch can be found in potatoes, rice, wheat and maize. Glycogen is the long-term store for energy and works the best in animal and fungal cells. The primary energy storage takes place in the adipose tissue and glycogen is made by the liver and muscles and also within the brain and stomach by glycogenesis. Glycogen serves as an energy reserve for animals and is the main form of carbohydrate stored in the animal body. It is insoluble in water and yields glucose on hydrolysis.

About Polysaccharides Provided by  

This article of deals with polysaccharides, the other two carbohydrates called monosaccharides and disaccharides have a separate article that includes important study material and therefore these concepts can be studied in-depth with the help of those notes provided by .

Three main types of carbohydrates are found in various natural and processed foods, they are as follows-

• Monosaccharides – The example of monosaccharides are glucose and Galactose.

• Disaccharides – The example of disaccharides are sucrose and maltose.

• Polysaccharides – The examples of polysaccharides are starch, glycogen and Cellulose. 

Polysaccharides are discussed as a very brief topic in the NCERT book of class 11, in chapter 9 called biomolecules.

Therefore provides effective study notes on the topic of polysaccharides, as some students may find it difficult to grasp this concept that is discussed in the NCERT book. After studying the study notes provided by students can get a comprehensive understanding of polysaccharides.

The study notes provided by on polysaccharides are an extremely important resource for students as they act as a reference guide. The objective of producing this study material is to help students get a comprehensive understanding of the topic that is being discussed and to help them get a good grade in the examination. The study material provided by is prepared by expert teachers who have years of experience in this field and are therefore well-versed in the concerned discipline. Class 11 and 12 study material on physics biology and chemistry is also useful for NEET aspirants as the basic foundation of NEET examination is the syllabus of class 11 and 12 physics biology and chemistry.

Students who are wanting to get a glance at the key concepts that are discussed in polysaccharides can go through the notes provided by , the link is easily accessible and it can be downloaded in a PDF format for free.

Key Concepts Taught in Chapter 9 Biomolecules Related to the Study of Polysaccharides-

9.1 How to Analyse Chemical Composition?

9.2 Primary and Secondary Metabolites

9.3 Biomacromolecules

9.4 Proteins

9.5 Polysaccharides

9.6 Nucleic Acids

9.7 Structure of Proteins

9.10 Metabolic Basis for Living

9.11 The Living State

9.12 Enzymes