1. Chemical Reactions and Enzymes Chapter 2-4

2. Chemical Reactions Chemistry is what life does!!! EVERYTHING that happens in an organism occurs because of CHEMICAL REACTIONS!!! Chemical reaction = a process that changes one set of chemicals into different chemicals

3. Chemical Reactions Reactants = the beginning substances (chemicals) Products = the ending substances Reactants  Products

4. Chemical Reactions Chemical reactions always involve the breaking of bonds in reactants and forming new bonds to make the products. There are always changes to the chemical bonds.

5. Chemical Reactions and Energy Chemical bonds are where the energy of a compound is stored. When bonds are broken, energy is released. When bonds are formed, energy is consumed.

6. Energy Changes All chemical reactions involve energy changes. The type of energy changes is one of the most important factors in determining if a chemical reaction will occur.

7. Chemical reactions that release energy often occur spontaneously. These reactions are called exothermic. Chemical reactions that absorb energy must have an outside source of energy. These reactions are called endothermic. Energy Changes

8. Activation Energy Activation Energy = the amount of energy needed to get a reaction started. Most of the time, the activation energy must come from an outside source.

9. Catalysts Catalyst = a substance that speeds up a chemical reaction by lowering the activation energy

10. Enzymes Many cells make catalysts called enzymes (a protein that acts as a catalyst). Cells then use enzymes to speed up chemical reactions that take place in cells.

11. Enzymes speed up reactions by providing a place for the reaction to occur. The effectiveness of enzymes can be changed by changes in: Temperature (best at 37 0 C or 98.6 0 F) pH (best around a neutral pH) Enzymes

12. Enzymes play essential roles in the chemical reactions of life. Chemical reactions control EVERYTHING that happens in living things!!!