Carbohydrates (CHO) - These are the principle energy storage molecules. They contain carbon (C), hydrogen (H), and oxygen (0) in a 1:2:1 ratio and are classified according to their size into monosaccharide, disaccharide, polysaccharide.
Monosaccharides are simple sugar having single chain or single ring structure which contains 3-7 carbon atoms. Example is glucose with 6 carbons, 12 hydrogens, and 6 oxygens.
Disaccharides: Double sugars are formed by dehydration reaction between 2 monosaccharides glucose + glucose ------ - > maltose + water. Disaccharides are too large to pass through cell membranes and must be digested to simple sugar units by hydrolysis (add water).
Polysaccharides are long chains of simple sugar molecules. The two major molecules of importance are starch, which is used for storage form for carbohydrate fuel in plants and glycogen, which is used for storage form for carbohydrate fuel in animals.
Function: It is ready source of cellular fuel & cellulose, is used for structural support in plants and carbohydrates help form cell receptors for recognition. Hence, option C is correct.