Introduction to Enzyme and EnergyThe study of energy transformations, or thermodynamics, is covered in the chemistry portion of the MCAT. However, it is useful to remind ourselves that the laws of thermodynamics apply as much to living organisms and cells as they do to inanimate objects. Cells therefore had to evolve methods of obtaining and processing energy that are in accordance with the general principles of energy transformations.
It is a general chemical principle that in order for a chemical reaction to proceed, a certain amount of energy, the activation energy, must be absorbed by the reactants to break the bonds already in place. One way of providing activation energy is simply to add heat to the reactants. This is what we do when we light a match to start a fire, which allows a combustion reaction to proceed. Living systems, however, cannot withstand the high temperatures necessary to overcome the activation energy barriers for biochemical reactions. Another method must exist to allow cells to facilitate and control chemical reactions. Enzymes are biological catalysts that facilitate reactions by lowering the necessary activation energy.