Carbohydrates are composed of single sugar units that make u starches which offer a ready source of your cell’s fuel. These units constitute monosaccharide, double-monosaccharide units called disaccharides and multiple-monosaccharide molecules while lipids are molecules that constitute hydrocarbons and make up the building blocks of the structure of living cells which stores energy in fat tissues for future uses. Both lipids and carbohydrates offer essential nutrients to diet. Both of them play an important role in absorption and digestion but have their own mechanic ways.