1. Chemical Reactions and Enzymes

2. Chemical Reactions A chemical reaction is an interaction between two chemicals. Chemical bonds are either broken or formed. The two parts of a chemical reaction are the REACTANTS and the PRODUCTS. Write an example chemical equation in the space below:

3. Chemical Reactions ACTIVATION ENERGY is the energy needed for a chemical reaction to start Most reactions in our bodies require a lot of energy to occur quickly enough to keep a cell working properly.

4. Chemical Reactions Draw a graph showing how activation energy is needed to start a chemical reaction:

5. Enzymes Enzymes are special proteins that speed up the rate of chemical reactions. Enzymes speed up chemical reactions by acting as CATALYSTS. Catalysts speed up the rate of a chemical reaction by lowering the activation energy needed to start the reaction.

6. Enzymes Draw a graph showing how activation energy is affected by enzymes:

7. How Enzymes Work 1.Enzymes bind to the reactants – these reactants are called SUBSTRATES. 2.Substrates bind to enzymes at a region known as the ACTIVE SITE. This forms the ENZYME-SUBSTRATE COMPLEX 3.The enzyme catalyzes the reaction and forms the products.

8. How Enzymes Work

9. Lock and Key Theory Each enzyme only works with one substrate. This is known as the LOCK AND KEY THEORY. How do enzymes know what substrates to bind too? Enzymes are very specific. They can only catalyze one particular substrate, however, there are 1000s of different enzymes.

10. Controlling Enzymes Concentration – Temperature – pH –

11. Controlling Enzymes This graph shows that: a.More enzymes are present at a higher pH. b.Pepsin is less sensitive to pH than trypsin. c.Pepsin is less effective at a low pH than trypsin. d.pH affects the activity rate of enzymes.

12. Controlling Enzymes If conditions are not ideal for an enzyme it will become DENATURED or destroyed. Three things that denature enzymes: 1. 2. 3.

13. Why are Enzymes Important? Digestion is needed to break down food into molecules we can use for energy. Digestive enzymes speed up chemical reactions in our body to make the process faster.

14. Catalase Catalase is an enzyme that is present in many cells, such as liver cells. It breaks down hydrogen peroxide into water and oxygen. Hydrogen peroxide a toxic chemical produced when sugars are broken down in cells. 2H 2 O 2 + Catalase  2H 2 O + O 2