1. Click to edit Master title style Click to edit Master text styles Second level Third level Fourth level Fifth level 11 Chemical Reactions: The Catalase Reaction An enzyme-catalyzed reaction between two molecules of hydrogen peroxide. Nome Baker, Ph.D. © 2009 Gnomus @ IMSLI

2. Click to edit Master title style Click to edit Master text styles Second level Third level Fourth level Fifth level 22 Bridge No. 1: A video review of the students’ experiments involving catalase Hyperlink to a demo video that will show students doing simple experiments that all students should do before beginning this activity. [Video to be taped. For now, see the earlier PD demo by Nome Baker; it needs editing.] [ The experimental session, in brief: The students test their hypotheses: 1) Do plant materials have an enzyme, catalase, that helps convert hydrogen peroxide to O 2 and H 2 O? 2) Does the O 2 formed behave as CO 2 did earlier in this system?]

3. Click to edit Master title style Click to edit Master text styles Second level Third level Fourth level Fifth level 33 Bridge No. 2: Web research. How many uses of hydrogen peroxide in humans, plants, & animals can you find? For many years hydrogen peroxide (H 2 O 2 ) was used on cuts to kill bacteria. Why isn’t it used for that purpose anymore? Oxygen bubbles appear when hydrogen peroxide comes into contact with blood cells. You will find out more about how this happens starting here.

4. Click to edit Master title style Click to edit Master text styles Second level Third level Fourth level Fifth level 44 Find the card……. Find the card that shows the reaction that took place in your experiment: 2 H 2 O 2 → 2 H 2 O + O 2 Hint: Models of the molecules are shown using special symbols for each element. Key for the molecular models

5. Click to edit Master title style Click to edit Master text styles Second level Third level Fourth level Fifth level 55 Key to symbols used: Each Answer Card shows molecular structures and uses different symbols for the various atoms in each molecule. This is the key to the elements shown: Next slide

6. Click to edit Master title style Click to edit Master text styles Second level Third level Fourth level Fifth level 66 Does this card show the reactant molecules in this reaction? 2 H 2 O 2 → 2 H 2 O + O 2 Key Yes No

7. Click to edit Master title style Click to edit Master text styles Second level Third level Fourth level Fifth level 77 Not quite. Look again. The reactants are two molecules of hydrogen peroxide (H 2 O 2 ): 2 H 2 O 2 → 2 H 2 O + O 2 Try again! These molecules are the products of the reaction.

8. Click to edit Master title style Click to edit Master text styles Second level Third level Fourth level Fifth level 88 Your right!. Neither molecule shown is hydrogen peroxide (H 2 O 2 ). One kind of molecule is H 2 O; the other is a gas you breathe (O 2 ). Which molecule is the gas and which one water? Go to the next challenge.

9. Click to edit Master title style Click to edit Master text styles Second level Third level Fourth level Fifth level 99 Does this card show hydrogen peroxide ( H 2 O 2 ) as the product of a catalyzed reaction? Reactants Product Yes No

10. Click to edit Master title style Click to edit Master text styles Second level Third level Fourth level Fifth level 1010 Your right! Good! You know the difference now between the reactants and the products of a reaction. Go to the next challenge. Reactants Product The metal catalyst (Pd or Au) greatly increases how fast H 2 reacts with O 2 in this reaction.

11. Click to edit Master title style Click to edit Master text styles Second level Third level Fourth level Fifth level 1111 Careful! Look out! In this reaction ( H 2 + O 2 → H 2 O 2 ), hydrogen peroxide is the product of a reaction catalyzed by a metal. In the main reaction that you are learning about, hydrogen peroxide molecules are the reactants in an enzyme-catalyzed reaction. Go back; look again! Be sure that you know the difference between the reactants and the products of a reaction.

12. Click to edit Master title style Click to edit Master text styles Second level Third level Fourth level Fifth level 1212 Find a card showing two hydrogen peroxide molecules reacting to form water and oxygen: 2 H 2 O 2 → 2 H 2 O + O 2 Click here to see if this is the right card.

13. Click to edit Master title style Click to edit Master text styles Second level Third level Fourth level Fifth level 1313 Does this card show this reaction: 2 H 2 O 2 → 2 H 2 O + O 2 ? Reactants Products Yes No

14. Click to edit Master title style Click to edit Master text styles Second level Third level Fourth level Fifth level 1414 How could Card A2 be right? You’re looking for a card with this reaction: 2 H 2 O 2 → 2 H 2 O + O 2 Reactants Products Try again 1)Compare the reactants: You’re looking for 2 H 2 O 2 ; Card A2 shows H 2 O 2 + RH 2. 2) Compare the products: You’re looking for 2 H 2 O + O 2 ; Card A2 shows 2H 2 O + R.

15. Click to edit Master title style Click to edit Master text styles Second level Third level Fourth level Fifth level 1515 Your right. That’s wrong! You’re looking for a card with this reaction: 2 H 2 O 2 → 2 H 2 O + O 2 Reactants Products Try another card. 1)Compare the reactants: You’re looking for 2 H 2 O 2 ; Card A2 shows H 2 O 2 + RH 2. 2) Compare the products: You’re looking for 2 H 2 O + O 2 ; Card A2 shows 2H 2 O + R.

16. Click to edit Master title style Click to edit Master text styles Second level Third level Fourth level Fifth level 1616 Reactants Products Does Card A3 show this reaction: 2 H 2 O 2 → 2 H 2 O + O 2 ? Yes No

17. Click to edit Master title style Click to edit Master text styles Second level Third level Fourth level Fifth level 1717 Your right. You’ve found the card with this reaction: 2 H 2 O 2 → 2 H 2 O + O 2 Reactants Products Next card Before learning more about catalase, the enzyme that catalyzes this reaction, look at examples of two other enzyme- catalyzed reactions involving hydrogen peroxide.

18. Click to edit Master title style Click to edit Master text styles Second level Third level Fourth level Fifth level 1818 Take another look! 2 H 2 O 2 → 2 H 2 O + O 2 You are looking for two H 2 O 2 (= HOOH) molecules reacting to form two H 2 O (= HOH) molecules and one oxygen O 2 (= OO) molecule. Make sure that you can find them on this card before you go on to the next card. Reactants Products Next card

19. Click to edit Master title style Click to edit Master text styles Second level Third level Fourth level Fifth level 1919 Compare these two different enzyme- catalyzed reactions: Reactants Products Next slide

20. Click to edit Master title style Click to edit Master text styles Second level Third level Fourth level Fifth level 2020 Cards A2 and A4 show similar reactions. In each one an O atom from H 2 O 2 removes two H atoms from a molecule to form two molecules of water. Reactants Products Model the reactions

21. Click to edit Master title style Click to edit Master text styles Second level Third level Fourth level Fifth level 2121 Build models of these reactions. Use beads or beans or candy or cards (representing different atoms and molecules) to make models of these two enzyme-catalyzed reactions: 2 H 2 O 2 → 2 H 2 O + O 2 H 2 O 2 + RH 2 → 2 H 2 O + R How do enzymes work?

22. Click to edit Master title style Click to edit Master text styles Second level Third level Fourth level Fifth level 2222 How the enzyme catalase works The next cards (A5 to A8) show four different stages of the enzymatic reaction that you have been studying: Try to put the cards in their correct order. [We will add a hyperlink to a url showing the structure of catalase.] See a molecular model of catalase.] Next slide

23. Click to edit Master title style Click to edit Master text styles Second level Third level Fourth level Fifth level 2323 Click on the card that shows the enzyme ready to catalyze the reaction. Hint: Before the reaction starts, none of the reactants and none of the products is attached to the enzyme. After the reaction the enzyme is free of reactants and product, ready for new reactants.

24. Click to edit Master title style Click to edit Master text styles Second level Third level Fourth level Fifth level 2424 Can you see why this is a late stage in the series? Try again

25. Click to edit Master title style Click to edit Master text styles Second level Third level Fourth level Fifth level 2525 You’re right! This represents the enzyme before any reactants are attached to it and also how the enzyme might look after all the products have left it free to be used again. So what happens next?

26. Click to edit Master title style Click to edit Master text styles Second level Third level Fourth level Fifth level 2626 Can you see why this is a later stage in the series? Try again

27. Click to edit Master title style Click to edit Master text styles Second level Third level Fourth level Fifth level 2727 True, this is an early stage in the reaction, but try to find a card that shows an even earlier stage. Try again

28. Click to edit Master title style Click to edit Master text styles Second level Third level Fourth level Fifth level 2828 This is the first step in the reaction. A hydrogen peroxide molecule is shown binding to the enzyme, catalase. 2 H 2 O 2 → 2 H 2 O + O 2 Do you know what happens next? The equation tells you what molecule still has to be attached before the reaction happens.

29. Click to edit Master title style Click to edit Master text styles Second level Third level Fourth level Fifth level 2929 Two molecules of hydrogen peroxide have to bind to the enzyme for the reaction to occur. Last step?

30. Click to edit Master title style Click to edit Master text styles Second level Third level Fourth level Fifth level 3030 At last! The reaction has taken place and the enzyme will be ready to act again as soon as the products of the reaction leave their binding sites. And finally…

31. Click to edit Master title style Click to edit Master text styles Second level Third level Fourth level Fifth level 3131 This is the first and last step in the sequence. The enzyme, catalase, is ready to act again. Check the sequence.

32. Click to edit Master title style Click to edit Master text styles Second level Third level Fourth level Fifth level 3232 Reviewing the reaction: You’ve now put your model in the correct order: A6 – A8 – A7- A5 (and back to A6).

33. Click to edit Master title style Click to edit Master text styles Second level Third level Fourth level Fifth level 3333 Now can you explain why bubbles form when you pour hydrogen peroxide on a cut? First you need to know: Blood forms at the site of the wound. Blood contains red blood cells. Red blood cells contain the enzyme catalase. Use the knowledge that you have gained in this lesson to explain: 1.What happens when you pour hydrogen peroxide on a cut. 2.What kinds of molecules form the bubbles?

34. Click to edit Master title style Click to edit Master text styles Second level Third level Fourth level Fifth level 3434 Acknowledgment Special thanks to the invaluable assistance of Ms. Nicole Ng and Ms. Asya Grigorieva in designing this unit. We are indebted to Dr. Ruth Dusenbery and to Dr. George W. Gagnon for their thoughtful criticisms and suggestions. This work was greatly influenced by the input from various middle school teachers, most notably by that of Mr. Alan Lee.

35. Click to edit Master title style Click to edit Master text styles Second level Third level Fourth level Fifth level 3535 An brief addendum follows You may end the slide show now. The next three slides are incomplete and are planned for the use of teachers.

36. Click to edit Master title style Click to edit Master text styles Second level Third level Fourth level Fifth level 3636 Student’s summary: [Link to the Learning Record. Response may be written and/or verbal as a presentation to the class. ] Review the catalase reaction using Cards A5 – A8 in the “correct” order to describe the catalase reaction in your own words. Try to include the following: What is the equation (write it) that describes the reaction? What are the reactants? ….the products of the reaction? What is the gas that forms when you add hydrogen peroxide to a fresh wound (e.g., a cut)? What is an enzyme and what does it do? Are any atoms lost during the reaction? If so, which?

37. Click to edit Master title style Click to edit Master text styles Second level Third level Fourth level Fifth level 3737 Review As a further review and as reinforcement of the concepts being taught, look at the video (insert link) of the experiment that you (the student) did in preparation for the lesson. You may also do the experiment [insert link] again--or for the first time if you’ve never done it. Review the “wrong” Answer Cards. What lessons can be learned from those (e.g., balanced equations, catalysts). Review the “Learning Aims”. (Insert Link) Insert link to an interactive test (concepts learned). [Test to be constructed.]

38. Click to edit Master title style Click to edit Master text styles Second level Third level Fourth level Fifth level 3838 Lesson Aims and Major Concepts; Understand the following: In a chemical reaction all of the atoms in the reactants appear in the products of the reaction. Chemical formulas and equations are used to describe a chemical reaction. A specific chemical equation describes your earlier, hands-on experiments in which oxygen molecules were the product you could observe. [Reminder: Students should perform hands-on experiments involving hydrogen peroxide and catalase-containing tissues before and/or after this lesson.] [Insert link to lesson plans for suggested experiments.]