1. Lecture #4 Enzymes Unit: Biochemistry

2. What are Enzymes & what do they do? Enzyme - Proteins that act as biological catalysts( a substance that speeds up the rate of a chemical reaction). You have thousands of enzymes in each of your cells, which are responsible for breaking down or building up macromolecules.

3. Why is this important for Life? Enzymes help to maintain HOMEOSTASIS. Without enzymes, chemical reactions would not happen quickly enough to sustain life Enzymes are responsible for your thinking, breathing, heartbeat, eating, walking, etc.

4. How do they do it? Enzymes speed up the rate of reaction by LOWERING THE ACTIVATION ENERGY needed to carry out the reaction. Activation Energy - The energy needed to start a chemical reaction. This makes it ‘easier’ for the reaction to take place.

5. Take two minutes to summarize what you have learned about what enzymes do and how they do it. Discuss with your shoulder partner- What do you understand well? What is a little confusing?

6. Enzyme Structure 2 parts: 1.A large protein molecule. 2. A non- protein portion called a cofactor. This is usually composed of a vitamin.

7. Enzyme Function Active Site- The exact spot on an enzyme where it binds to the molecule(s) it is going to break down or build up. Substrate: The molecule that the enzyme attaches to and acts upon

8. Importance of the non-protein portion of an enzyme Without this, the enzyme would not be able to attach to the substrate molecule. The vitamin portion (cofactor)makes binding possible. This is why a good balanced diet is so important!

9. Enzymes & their substrates are similar to a lock & its key Enzymes are very specific, generally catalyzing only one chemical reaction. Ex: Maltase only Breaks down maltose.

10. What happens when an enzyme attaches to its substrate? 1.Enzyme attaches to its substrate 2. The activation energy of the reaction decreases 3. Reaction is complete when the products are formed. 4. The enzyme detaches and is free to catalyze more reactions.

11. Example of Enzyme action- Digestion of Starch Starch is composed of thousands of glucose units. Salivary Amylase: Enzyme found in saliva that begins the breaks down starch Amylase breaks starch into maltose units (double glucose) Maltase: another enzyme (not in saliva)breaks maltose into two glucose units.

12. Take two minutes to summarize what you have learned about the structure of enzymes & what occurs when enzymes attach to their substrate molecule. Discuss with your shoulder partner- What do you understand well? What is a little confusing?

13. How long does it take an enzyme to work? Rate of Reaction - The amount of time it takes to convert a particular amount of substrate to the products of the reaction. This can vary from enzyme to enzyme. What factors affect enzyme activity? Lets find out!

14. Factors that affect enzyme activity Temperature Enzymes produced by human cells generally work best at temperatures close to 37°C, the normal temperature of the human body. pH Enzymes work best at certain pH values. For example, the stomach enzyme pepsin, which begins protein digestion, works best under acidic conditions.

15. Factors that affect enzyme activity Chemical Contamination Example - heavy metals such as mercury & lead These elements are toxic to plants and animals. Why? Atoms of these elements attach to enzymes in such a way that causes enzyme molecules to clump together and are rendered inactive. This means that thousands of biochemical reactions cannot occur as they should.

16. Take two minutes to summarize what you have learned about the factors that affect enzyme activity. Discuss with your shoulder partner- What do you understand well? What is a little confusing?

17. Enzyme Catalysts video http://videos.howstuffworks.com/discovery/287 33-assignment-discovery-enzyme-catalysts- video.htm