How do enzymes increase the reaction rate?

Enzymes bind to the substrate forming an enzyme-substrate complex through binding at the active site. This reduces the activation energy (the difference in free energy between substrates and transition state) of the reaction through the bending of bonds and the formation of the transition state. The decreased activation energy allows more substrate molecules to have sufficient energy to reach the transition state. Through this process, the enzyme increases the rate of reaction, permitting reactions that may have been to slow to proceed.