Answer:
1. Activation energy is the energy needed to start a reaction.
2. A substrate is a substance that binds to a protein. It is the substance a protein "acts" on.
3. A catalyst is a protein that speeds up reactions. Catalysts lower the activation energy of a reaction, allowing the reaction to occur faster.
4. A product is a substance formed by a chemical reaction. In a chemical reaction, you have the reactants which are the substances you start with, and the products, which are the substances that are created.