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.
Endothermic reactions are the opposite. The new bonds require more energy. This comes from heating the substances, or sometimes, comes from the surrounding environment. Absorbing heat energy from the environment makes everything decrease in temperature so the reaction 'feels' cooler.