Unit - - Carbohydrates and Energy carbohydrates are reduced to this state before absorption and utilization. They contain - carbon atoms and are accordingly termed triose, tetrose, pentose or hexose. (i) Biose: C H O (e.g.)Glycolic aldehyde (ii) Triose: C H O (e.g.)Glyceraldehyde and Dihydroxyacetone. They occur in plant and animal tissues in small amounts and are derived from the breakdown of glucose.
(iii) Tetroses: C H O (e.g.) Erythrose, Threose (iv) Pentoses: C H O (e.g.) Arabinose, Xylose, Ribose and Deoxyribose. (v) Hexoses: C H O .They are further sub-divided into groups(i.e) Aldoses or sugars containing aldehyde group(e.g.) Glucose, . Composition of carbohydrates Carbohydrates are so called because they contain carbon with hydrogen and oxygen in the same proportion as in water ( : ). The general formula is C n H 2n O n .
Classification of carbohydrates Carbohydrates are classified according to the number of saccharide (sugar) groups present. They are broadly classified as simple carbohydrates and complex carbohydrates. The simple carbohydrates include monosaccharides(Single sugar) and disaccharides (Double sugars). Complex carbohydrates include starch, glycogen and fibers.
The classification of carbohydrates is schematically represented below: . . Simple Carbohydrates A) Monosaccharides They have one saccharide group and are the simplest form of carbohydrates. All Carbohydrates Simple Complex Monosaccharides Disaccharides Polysaccharides Glucose Fructose Galactose Maltose Lactose Sucrose Starches Fibers Glycogen Fig .
: Classification of carbohydrates - - Carbohydrates and Energy b) Lactose (Milk sugar): It occurs in the milk of mammals. Cow’s milk and buffalo’s milk contain % of lactose, while human milk contains about % of lactose. Lactose is hydrolysed to glucose and galactose by the enzyme lactase present in the intestinal juice. galactose and mannose as well as Ketoses or sugars containing ketone group(e.g.) Fructose.
Major monosaccharides a) Glucose (Dextrose or grape sugar): It serves as the main source of energy in the body. It is abundantly found in nature. It is found in sweet fruits such as grapes, berries, oranges