Biomolecules -II

Thursday, January 21, 2010

Maltose is made up of two a-D-glucose (in pyranose form) units held together by a(14) glycosidic bond. As there is a free aldehyde group at C-1 position of the second glucose molecule, maltose is known as reducing sugar. Maltose forms osazones. The enzyme that hydrolyses maltose is maltase.
Lactose is made up of b-D-galactose and b-D-glucose held together by b(14) glycosidic bond. As the aldehyde group at C-1 position of glucose is free, lactose is known as reducing sugar. Lactose forms osazones.

Polysaccharides - Introduction
They consist of repeat units of monosaccharides or their derivatives. These units are held by glycosidic bonds. These carbohydrates liberate large number of monosaccharide molecules on hydrolysis. They are colorless and tasteless. So, they are called non-sugars. They are concerned with two important functions - structural and storage of energy. Some examples of polysaccharides are starch, cellulose, glycogen and dextrins. However starch and cellulose are the most important of these.

Mucopolysaccharides are the heteroglycans made of repeating units of sugar derivatives like amino sugars and uronic acids. These are known as glycosamino glycans (GAG). Important mucopolysaccharides are hyaluronic acid, chondroitin sulphate and heparin.

Structures of Starch and Cellulose
Starch occurs in all plants, particularly in their seeds. The main sources are wheat, maize, rice, potatoes, barley and sorghum.
Functions of Carbohydrates
Carbohydrates participate in a wide range of functions:
* Carbohydrates are most abundant dietary source of energy for all organisms.
* They supply energy and serve as storage form of energy.
* Carbohydrates such as glucose, fructose, starch, glycogen, etc. provide energy for functioning of living organisms.

Proteins - Introduction
Proteins are the high molecular mass complex biopolymers of amino acids and organic compounds that are most important to life. They are essential for growth and maintenance of life. They are high molecular weight, nitrogen rich substances that are present all living cells of animals and plants. They occur in every part of the cell. They are composed of 20 amino acids, which are repeatedly found in the structure of proteins. These amino acids are liberated when proteins are hydrolyzed. Proteins are the polymers of -amino acids.


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