ABSTRACT
A knowledge of thermodynamics, which is the description of the relationships among the various forms of energy and how energy affects matter, enables one to determine whether a physical process is possible. The first and second laws of thermodynamics are combined in the thermodynamic function, free energy. For a biochemical reaction to proceed, the energy barrier needed to transform the substrate molecules into the transition state has to be overcome. An energetically unfavorable reaction is often driven by linking it to an energetically favorable reaction, such as the hydrolysis of adenosine triphosphate. The difference in free energy between the substrate and the transition state is termed the Gibbs free energy of activation. A chemical reaction usually exists in a state of dynamic equilibrium, where although new molecules of substrate and product are continually being transformed and formed, the ratio of substrate to product remains at a constant value.
