Question

How does adding a catalyst make a transient species more stable so that the reaction occurs?

Answer 1

The catalyst has higher affinity to transition state than to reactant or product. It binds to the transient transition state species and then this results in lower of activation energy. When the substrate binds, the enzyme may stretch or distort a key bond and weaken it so that less activation energy is needed to break the bond at the start of the reaction. In many cases, the transition state of a reaction has a different geometry at the key atom (for instance, tetrahedral instead of trigonal planar). By optimizing binding of a tetrahedral atom, the substrate is helped on its way to the transition state and therefore lowers the activation energy, allowing more molecules to be able to turn into products in a given period of time. The enzyme stabilizes the transition state through various ways. Some ways an enzyme stabilizes is to have an environment that is the opposite charge of the transition state, providing a different pathway,and making it easier for the reactants to be in the right orientation for reaction.