Bioenergetics is the study of energy transformations in a living organism. It encompasses the fundamental energy-harvesting processes of photosynthesis and respiration, as well as other metabolic reactions that require or release energy. Energy in a cell is used for reproduction, synthesis of vital molecules, movement, and other basic functions. Virtually every reaction in the cell either requires or releases energy.

According to the Second Law of Thermodynamics, the entropy of the universe increases with every chemical change. And yet, in the face of this increasing disorder, living organisms carry out exceedingly complex reactions and remain highly organized. How is this possible? This maintenance of order within the living system is accomplished by constantly taking in high-energy, well-ordered materials from the environment, and excreting low-energy, less-ordered waste products. Glucose, for instance, is a high-energy compound used as a food source. Much of its energy is extracted during glycolysis and...