From chemistry to biochemistry to catalysis to movement.

Mechanisms of chemical reaction can often be predicted by determining the dependence of the lifetime of reaction intermediates on the structure of the reactants. When there is no lifetime in the presence of another reactant or catalyst the reaction proceeds through an enforced concerted mechanism. Noncovalent binding interactions between enzymes and their substrates provide a major contribution to catalysis by decreasing entropy and by destabilizing the ground state relative to the transition state, as well as by covalent and noncovalent chemical interactions with the substrate. Movement in biological systems, such as muscle contraction and the active transport of ions, is generally brought about through a series of alternating chemical and vectorial steps that involve a series of changes in the specificity for catalysis of the chemical and vectorial reactions. These changes divide the overall reaction into segments so that neither the chemical nor the vectorial reaction will be completed unless the other is also completed.