Bioenergetics
Bioenergetics, study of the processes by which living cells use, store, and release energy. A central component of bioenergetics is energy transformation, the conversion of energy from one form to another. All cells transform energy. Plant cells, for example, use sunlight to make carbohydrates (sugars and starches) from simple inorganic chemicals. In this process, called photosynthesis , radiant energy from the sun is converted into stored chemical energy. If these plant carbohydrates are eaten by an animal (see Food Web ), they will be broken down and their chemical energy turned into movement (kinetic energy), body heat (radiant energy), or new chemical bonds (see Adenosine Triphosphate ; Citric Acid Cycle ; Metabolism ). In all such transformations, some energy is lost to the environment. This lost energy, which is no longer available for useful work, is called entropy. The second law of thermodynamics states that any system tends to run down—that is, increase its entropy—over time