Elementary plant Biochemistry and Biotechnology (2+1)

Occurrence and importance

• The carbohydrates comprise one of the major groups of naturally occurring biomolecules. This is mainly because; the light energy from the sun is converted into chemical energy by plants through primary production and is transferred to sugars and carbohydrate derivatives. The dry substance of plants is composed of 50-80% of carbohydrates. The structural material in plants is mainly cellulose and related hemicelluloses. Starch is the important form of storage polysaccharide in plants.Pectins and sugars such as sucrose and glucose are also plant constituents.Many non-carbohydrate organic molecules are found conjugated with sugars in the form of glycosides
 
• The carbohydrates in animals are mostly found in combination with proteins as glycoproteins, as well as other compounds.The storage form of carbohydrates, glycogen, found in liver and muscles, the blood group substances, mucins, ground substance between cells in the form of mucopolysaccharides are few examples of carbohydrates playing important roles in animals.Chitin found in the exo-skeleton of lower animals, is a polymer of N-acetyl glucosamine. Carbohydrates are also universally found in other polymeric substances.
 
For example,
• Fats are fatty acid esters of a sugar alcohol, glycerol.
• Ribose and deoxyribose are constituent of nucleic acids


• Moreover, in all living forms, the energy needed for mechanical work and chemical reactions are derived from carbohydrates.Adenosine triphosphate and related substances that contain ribose as a constituent are key substances in energy storage and transfer. The carbon skeletons of almost all organic molecules are derived from carbohydrates.Besides, the carbohydrates are the basic raw material of many important industries including sugar and sugar products, starch products, paper and wood pulp, textiles, plastics, food processing and fermentation.