The simplest forms of carbohydrates are known as monosaccharide. These have a general molecular formula given by Cx(H2O)y. The values of x and y differ for different monosaccharide. Monosaccharide have a linear carbon chain to which are attached one carbonyl or C=O group and one hydroxyl -OH group.
Some examples of monosaccharide are glucose, fructose and ribose. Complex carbohydrates in the human body have to be broken down by the action of enzymes to monosaccharide before which they can be absorbed. While complex carbohydrates are usually insoluble in water, monosaccharides are soluble in water.