Now enzymes are these protein molecules that assist is the chemical reactions that take place within the human body. So before we discuss the major chemical processes that take place within the human body such as glycolysis, fermentation or cell respiration, let's discuss and define what the role of the enzyme is within the human body. So enzymes are biological molecules, are proteins that increase the rate of the reaction. They increase the speed of that reaction by decreasing the activation energy of that reaction. Now recall that the activation energy is basically the amount of energy that must be inputted into our reaction to overcome that energy barrier, to basically reach that transition state and transform the reactants to the product. So to see what we mean, let's take a look at the following diagram.