Dr Praveen Kumar Agrawal is teaching live on Unacademy Plus
COURSE BIOMOLECULES Lesson Carbohydrates Classification Dr. Praveen Kumar Agrawal
CARBOHYDRATES Carbohydrates are the basic component of our food and are also the chief source of energy for our body. Carbohydrates are widely distributed in plants and animal. They play structural as well as functional role. They are also called saccharides or sugars. In plants, carbohydrates are synthesized from CO2 and water during photosynthesis. . carbohydrates constitute about 80 % of the dry weight of the plants. Animals can synthesize a little carbohydrate from proteins and fats (gluconeogenesis), but the bulk of animal carbohydrate comes, ultimately from the plants.
Chemistry of carbohydrates Carbohydrates (Fr. hydrate de carbone) are the hydrates of carbon (carbon associated with water) They have carbon, hydrogen and oxygen in the ratio 1:2:1. (The ratio of hydrogen and oxygen in carbohydrates is the same asfound in water) simple carbohydrates have general empirical formula-C,H2nOn. All carbohydrates contain at least one asymmetrical (chiral) carbon and are, therefore, optically active. .Simple carbohydrates are the aldehydic or ketonic derivatives of polyhydroxy alcohols (alcohols, which have more than one -OH groups).
Classification of carbohydrates Major classes Name Structure Relevant examples Triose Tetrose Pentose Hexose Heptose Nanose Disaccharides 3 carbon atoms C3H603 4 carbon atoms C4Hg04 5 carbon atoms CsH100s 6 carbon atoms CoH1206 7 carbon atoms CyH1407 9 carbon atoms CgH1808 Glyceraldehyde, Dihydroxyacetone Erythrosee Ribose, Ribulose, Xylulose, Deoxyribose Glucose, Galactose, Mannose, Fructose Sedoheptulose Neuraminic acid (sialic acid) Monosaccharides Two monosaccharide units are Maltose, Sucrose, Lactose, Gentiobiose, joined together Melibiose Trisaccharides Three monosaccharide units are Rabinose, raffinose, Gentianose Tetrasaccharides Four monosaccharide units are Scorodose, Stachyose Pentasaccharides Five monosaccharide units are Verbascose joined together joined together joined together Oligosaccharides Polysaccharides Many (thousands) units of monosaccharides are joined together. Glycogen, Cellulose, Starch