Final answer:
A catalyst, and particularly an enzyme in biological systems, decreases the activation energy of a chemical reaction. Enzymes work by stabilizing the transition state, allowing the reaction to proceed more rapidly without altering the free energy change (∆G) of the reaction.
Step-by-step explanation:
The component that decreases the activation energy of a chemical reaction is known as a catalyst. Specifically, in biological systems, these catalysts are called enzymes. Enzymes are special molecules, usually proteins, that facilitate biochemical reactions by binding to the reactant molecules and orienting them in such a way that the reaction can take place more easily. By doing this, enzymes reduce the activation energy that is otherwise required for the reaction to proceed, thus speeding up the rate of the reaction without being consumed themselves in the process.
For example, during a reaction, the reactant molecules must collide with proper orientation and sufficient energy to surpass the activation energy barrier. An enzyme stabilizes the transition state and decreases the amount of energy required to reach this state, thereby increasing the rate of the reaction. It's crucial to realize that while enzymes lower the activation energy, they do not alter the overall free energy change (∆G) of the reaction, nor do they change the reaction from endergonic to exergonic or vice versa.