1)    Carbohydrates   Constituents of carbohydrates are “ Carbon , Hydrogen  and Oxygen ".  The general formulae of carbohydrates is cx (H2O) y.  In carbohydrates always Hydrogen and Oxygen are in the ratio 2:1.  They are made of saccharide units (literally sugar) - a prefix (mono-, di-, poly-) denotes how many units.   Carbohydrates are classified as Monosaccharides, Disaccharides and polysaccharides.