Enzymes are proteins that speed up the rate of a chemical reaction without being used up.
Enzymes are usually specific to particular substrates.
The substrates in the reaction bind to active sites on the surface of the enzyme. The enzyme-substrate complex then undergoes a reaction to form a product along with the original enzyme. The rate of a chemical reaction is affected by the total number of enzymes as well as the concentration of substrates. We can describe the reaction rate with a simple equation to understand how enzymes affect chemical reactions. In the absence of enzymes, the rate of a reaction can be thought to increase linearly with substrate concentration.