Describe several mechanisms by which enzymes lower activation energy?

Question

Describe several mechanisms by which enzymes lower activation energy?

Answer 1

There are two ways that I know an enzyme ( the catalyst of a reaction) can lower the activation energy. ALL enzymes lower the activation energy by lowering the potential energy(stabilizing) of the transition state (Note the transition state is not the same as an intermediates. Intermediates are compounds that can be separted and stored. Transition states are extremely unstable molecules with partially formed and broken bonds.). The electrons in a transition state can be stabilized by the enzyme when they interact with another ion, atom, or molecule.

Some but not all enzymes catalyze reactions by providing an alternate mechanism for the reaction, a new, lower energy pathway. In this case the enzyme produces intermediate(s) (that is eventually used up) to synthesize a product. For example:

Substrate + enzyme --> C

C + B --> product + enzyme

C represents an intermediate, B is a another substrate

Then again only some enzymes provide alternate mechanisms, but ALL enzymes stabilize transition states.

Answer 2

Enzymes bind temporarily to one or more of the reactants of the reaction they catalyze. In doing so, they lower the amount of activation energy needed and thus speed up the reaction.

Eg: Catalase. It catalyzes the decomposition of hydrogen peroxide into water and oxygen.

2H2O2 -> 2H2O + O2

One molecule of catalase can break 40 million molecules of hydrogen peroxide each second.

By providing an alternative reaction route and by stabilizing intermediates the enzyme reduces the energy required to reach the highest energy transition state of the reaction.

E+S(SUBSTRATE)---------->E-S(COMPLEX)-...

enzymes lower the energy by acting on a certain substrate

forming E-S complex WHICH enter the reaction and accelerate it by raising the substance ground state to the transitional state (increase the free energy of the substrate needed to produce the product so the energy needed to start the reaction will decrease ). Enzymes are not consumed during the reaction.