The origin of replication (also called the replication origin) is a particular sequence in a genome at which replication is initiated.
It is the interaction of two or more substances, resulting in chemical changes in them. Chemical reactions take place when some kind of energy is supplied to them. The supplied energy may be in the form of heat, light or mechanical shaking for proper contact between the reactant molecules or electricity.
Almost all processes in a biological cell need enzymes to occur at significant rates. To add on, enzymes enable multiple reactions all in one ''flask,'' which is important in the cell b/c many reactions can occur at once. To prevent unwanted reactions, enzymes are specific to certain steps in the reaction.