|Catalytic Reaction; credit: Fvasconcellos|
Enzymes are macromolecules that catalyze chemical reactions within a living organism. Most are proteins, but there are also RNA enzymes which aid in protein synthesis. By speeding up reactions, enzymes allow organisms like us to perform vital functions in a timely manner. Without them body processes would take forever to complete.
Chemical reactions involve the breaking of bonds and forming of new ones. The investment of energy required to start this process is known as the activation energy commonly written Ea. Molecular bonds only break after reactants have adsorbed enough energy to reach a state of instability, after which they swap molecules and simultaneously lose that energy. Often the energy absorbed is in the form of heat, which causes the molecules to become agitated so they speed up and collide more frequently. The Ea creates a barrier in that the reaction cannot occur unless enough energy is provided, be that in the form of higher temperature.
For living organisms, exposing their bodies to the heat necessary to facilitate reactions would be impractical. Not only would it damage or kill tissue, but there would be no control over which reactions were occurring. Enzymes solve both problems by lowering the Ea barrier and targeting specific processes. This allows any number of reactions to occur throughout a living system when and where they are needed, and at normal temperatures.