Biochemistry is the study of chemical reactions in living beings, and of biological molecules in general. It is important to cell biology and physiology. The study of biochemistry involves enzymes, nucleic acids, carbohydrates, sugars, proteins, and lipids. In the body, most of the molecules are polymers built of long chains of smaller molecules. Biochemistry studies the chemical transformations which produce these small building-block molecules, and which produce energy from food.