Brief Intro to Enzymes

1. Brief Intro to Enzymes • We’re going to move through this ppt quickly • At most, jot down a note here and there • This is just meant to be a brief introduction to enzymes before we start the lab & a review of the prompts

2. Enzymes Biological Catalysts

3. Enzymes are Biological Proteins • Big molecules (check out your scale….) • Many of our genes code directly for enzymes • Estimated to be about 75,000 different types in the human body

4. Enzymes Do…. Do Not… • Speed up chemical reactions • Allow reactions to occur with less energy input • Provide energy for the reaction • End up altered or used up or in the product • Change the net effect of the reaction (the products are the same with or without an enzyme)

5. Chemical Energy • Potential energy • Energy stored in the arrangement of bonds • Can be converted into kinetic energy forms (heat, light, sound, movement etc.) like a spring

6. Heat Energy • Is how much the atoms/molecules are moving • More heat/temperature = more movement

7. All reactions require an initial input of energy • Something has to get the reaction started • Called the activation energy • i.e. lighting the fuse on a bomb

8. Why? • It takes energy to get bonds to break • More energy = moving faster = molecules can break apart

9. Energy I.e. • It takes energy to split lactose and water • Energy is released when new bonds are formed Energy

10. Some reactions are Endothermic Exothermic • The products have MORE potential energy than the reactants • These reactions absorb energy/heat • i.e. a ice pack • The products have less energy than the reactants • Energy/heat is released • I.e. TNT

11. Endothermic vs. Exothermic Endothermic Exothermic • Net effect is energy into the products • Net effect is energy released from reactants

12. So What Do Enzymes Do? • They allow bonds to be broken at lower temperatures • Thus they lower the activation energy • So reactions can happen more easily with less input of energy (at lower temps)

13. Potential Energy Diagram

14. Enzyme Terminology • Substrate = reactant • Active site = place on enzyme where the substrate can bind

15. Enzymes are Specific! • Only substrates that “match” the active site can be catalyzed • Like a lock and key

16. Enzyme Catalysis Lab • You will be testing how different factors affect the rate of an enzyme-catalyzed reaction • You will spend the rest of class today designing your own experiment. You must finish your final draft and have me check it PLUS your materials list.

17. Your Experiment • Should test how 1 factor affects the rate of hydrogen peroxide decomposition • Should include 3 experimental levels (ex: 3 different types of potato NOT 3 trials of each level…unless you have time ) and a control trial • Should be conducted in a single block period NEXT TUESDAY!

18. You Are Writing Your Procedure • Needs to be thorough! • Nothing is too small to put in procedures • i.e. put on glasses, rinse cups, cleaning materials, safety gear.

19. Your Procedure Con. • Set up your entire experiment at once • Don’t say “I will redo steps 1-5”…that’s repetitive and inefficient • Make all of the catalase you need at once, put it into all the test tubes at once etc. • Anything you will need to do should be in the procedure • I.e. rinsing cups, measuring amounts of water, how long you let the reaction run etc. • Anything you will need to use should be in the procedure • i.e. graduated cylinder, scale etc.

20. Safety • No open flames- any heating should be done with a hot water bath • Goggles must be worn • Gloves must be worn • Immediately report any broken glassware!

21. Steps • Complete the prelab ws- follow the directions • Your individual procedure can be very rough • When approved, write a final procedure as a group • Include ideas from everyone’s procedure and be completely thoroughly including your materials list • Show this group procedure to Reineke by 11:00 • Once approved fill out the “enzyme final draft ws”- NOTE each person needs a copy for the HW • By 11:30 give me a final procedure for your group and a list of materials • Before you leave you must divide the work for the HW “drawn procedure” complete the sheet individually

22. Ex: Basic Procedure (written) • Using the scale, measure out _g of peeled potatoes • Using the mortar and pestle, mash up the _g of potato • Using a graduated cylinder place _ml of water into a cup and add the peeled potatoes • Thoroughly mix the mashed potatoes and water • Keep on ice • Using a pipette add 1ml of hydrogen peroxide to a clean test tube • Using a different pipette add 1ml of catalase solution • Observe and measure ________

24. Scoring • Prelab /5 (individual) • Procedure /5 (group) • Draw Procedure /5 (individual) • Results/Graphs /5 (individual) • Conclusion /10 (individual)

25. Scoring Continued • Any material you have to ask for that wasn’t on your procedure/materials sheet = -1 point • Any question you have to ask about your procedure = -1 point • No trading of materials between groups. If I see it you both lose a point (i.e. if you don’t identify that you need a scale, you lose a point if you use it)

26. A Few Notes • You will mash your own potatoes to make the catalase solution. • As a standard you want to mash about 1g of potato per 2ml of water. You figure out how much you need and the ratio • As a standard you should react about 1ml of peroxide with 1ml of catalase solution