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The structure and function of Carbohydrates

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Introduction

The structure and functions of carbohydrates. Carbohydrates comprise a large group of organic compounds which contain oxygen, hydrogen and carbon. The term "carbohydrate" derives from their general formula of C n (H 2 O) n where the ration of H: O is 2:1. Carbohydrates are divided into three main groups; monosaccharides, disaccharides, Oligosaccharides and polysaccharides. A Monosaccharide is a simple sugar such as fructose, glucose, and ribose. It is the simplest form of carbohydrate; therefore, it cannot be broken down to simpler sugars by hydrolysis. These all have the formula (CH2O)n, where n can be between 3 and 7. It is a sugar that constitutes the building blocks of a more complex form of sugars such polysaccharides. The most common monosaccharide is glucose, which is a hexose sugar, so has the formula C6H12O6. Glucose has a stable ring structure and there are two structural isomers; alpha and beta glucose. The difference between alpha and beta glucose is the differentiation of the side groups at C1. ...read more.

Middle

Disaccharides are formed when two monosaccharides are joined together by a glycosidic bond resulting with the loss of water. Disaccharides are formed by condensation reactions and broken down by hydrolysis Maltose is fromed when two glucose molecules react. It is formed on digestion of starch by amylase, because this enzyme breaks starch down into maltose. Sucrose is formed when glucose reacts with fructose. It is common in plants because it is less reactive than glucose, and it is their main transport sugar. It is known as table sugar which is a component of human nutrition. But if sucrose is consumed too much it can lead to tooth decay and obesity. Lactose is formed when galactose reacts with glucose. It is found only in mammalian milk, and is the main source of energy for infant mammals. Polysaccharides are long chains of many monosaccharides joined together by glycosidic bonds. Starch is the plant storage polysaccharide. ...read more.

Conclusion

Hundreds of these chains are linked together by hydrogen bonds to form cellulose microfibrils. These microfibrils are very strong and rigid, and give strength to plant cells, and therefore to young plants and also to materials such as paper, cotton and sellotape. The glycosidic bond cannot be broken by amylase, but requires a specific cellulase enzyme. The only organisms that possess a cellulase enzyme are bacteria, so herbivorous animals, like cows and termites whose diet is mainly cellulose, and have a mutualistic relationship with the bacteria in their guts so that they can digest cellulose. Other polysaccharides include Chitin which is found in fungal cell walls and the exoskeletons of insects and Lignin found in the walls of xylem cells, is the main component of wood. Oligosaccharides are another form of carbohydrate and are small polymers of monosachrides and are connected with each other through bonds called glycosidic bonds. They have many functions for example the molecules are found on the plasma membrane of animal cells where they can play a role in cell-cell recognition. ...read more.

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