General objective of this lecture is to present on Rates of Reactions and Enzymes. Enzymes are biological catalysts. They help the reactions that occur in our bodies by controlling the rate of reaction. The rate at which the reaction happens depends on four things: the temperature of the reactants; their concentration; their surface area and whether or not a catalyst is used. Two common ways of Rates of Reactions: (1) Measure how fast the products are formed and (2) Measure how fast the reactants are used up.