Enzyme

Enzymes can act in serveral ways, all of which lower the energy required for the chemical reactions to occur:
1. Lowering the activation energy by creating an environment in which the transition state is stabilized
2. Lowering the energy of the transition state, but without distorting the substrate, by creating an environment with the opposite charge distribution to that of the transition state
3. Providing an alternative pathway. For example, temporarily reacting with the substrate to form an intermediate ES complex, which would be impossible in the absence of the enzyme
4. Reducing the reaction entropy change by bringing substrates together in the correct orientation to react

because enzyme is very active,if it is in optimum temperature and ph,it can speed up the reactions of the cells.