Enzyme Reactions: Effects of Concentration, pH, and Temperature

1. Agenda • Collect Pre-lab #5 • Lab Quiz #4

2. LAB 5: Enzymes

3. Enzyme Reactions ENZYME SUBSTRATE PRODUCT

4. Enzyme Reaction Rate • Effect of enzyme concentration on reaction rate

5. Enzyme Reaction Rate • Effect of substrate concentration on reaction rate

6. Enzyme Reaction Rate • Effect of pH on reaction rate

7. Enzyme Reaction Rate • Effect of temperature on reaction rate

8. Catecholase Catechol + O2 Benzoquinone Colorless Brown Catecholase (Potato Extract)

9. Catecholase • Present in plants (potatoes) • Reaction seen when potatoes or apples turn brown

10. Exercise 1 – Effect of enzyme concentration on Reaction Rate • Color chart method • Color change = what? • Look at the set-up of the experiment. Answer questions about experimental design. • Set up the experiment using the procedures on the back and the Table on the front. • Watch reactions for 5 minutes, inverting to mix every minute. • Record the color of each tube after each minute (different from procedures)

11. Exercise 1 – Effect of enzyme concentration on Reaction Rate • THINGS TO NOTE: • Catechol is toxic (don’t drink it; wash hands) • Catechol waste goes in the bucket • Keep potato extract on ice • Be accurate!!

12. Part 2: Designing an Experiment • Design an experiment to test one of the following using catecholase: • pH buffers (counter) • Temperatures (Water baths) • Different substrates (Sugars and starch) • Salt concentration (counter)

13. Part 2: Designing an Experiment • Things to think about: • What will your control group be? • # of trials (replication)? • Volumes of different solutions? • Timing of reactions / when you measure color?

14. Part 3: Designing an Experiment • LAB REPORT #1 due next week • Look at the format at the end of the lab manual

15. How to Write a Scientific Paper • See Appendix B in lab manual • Look at peer review sheet

16. Writing a Lab Report • TYPED • 12 point font • May be single or double spaced

17. Writing a Lab Report • TITLE • Should tell what will be in the lab report • Good format is “The effect of the independent variable on the dependent variable”

18. Writing a Lab Report • INTRODUCTION • Background information about your experiment • General background someone would need to understand the topic • Specific background someone would need to understand your experiment • Important vocabulary • Very brief summary of your experiment • Question you’re addressing • State hypothesis • Explain why the hypothesis is worth investigating • Make predictions about results • 3-5 paragraphs

19. Writing a Lab Report • MATERIALS and METHODS (Procedure) • Detailed description of what you did so that someone else can replicate your experiment • Discuss your experimental design • State the independent and dependent variable • Identify control, constants, replication • Use the passive past tense (“the solution was heated” not “we heated the solution”) • Write using paragraphs • Be specific (measurements, units, etc) • About 2-3 paragraphs

20. Writing a Lab Report • RESULTS • Even if it doesn’t support your hypothesis, it’s still a result! • Present ALL data in an organized, meaningful form (quantitative, qualitative) • Data in table(s), Graph(s), or Figure(s) (pictures) • A paragraph that presents DATA, does NOT explain why you observed those results. • 1 paragraph plus table, graph, etc

21. Writing a Lab Report • DISCUSSION (Conclusions) • Summarize your problem and hypothesis (review) • Summarize your data by discussing specific data in sentences • Discuss how your results answer (or do not answer) your original question • How do your results fit with what you know? • Importance of results • Is your hypothesis supported by this data or not? • Did you confirm your predictions?

22. Writing a Lab Report • DISCUSSION (Conclusions) • IF YOUR HYPOTHESIS WAS SUPPORTED: • Evaluate possible explanations for the results based on background information. • Answer the original question. • Explain things that could be improved in your experiment • Discuss additional experiments that would add to your results.

23. Writing a Lab Report • DISCUSSION (Conclusions) • IF YOUR HYPOTHESIS WAS NOT SUPPORTED: • Evaluate possible explanations for the results based on any experimental errors OR personal misconceptions / lack of background information. • If your experiment didn’t work due to errors, you CAN NOT answer original question. • Explain things that could be improved in your experimental design or how you could correct errors • Discuss additional experiments that would add to your results.

24. Writing a Lab Report • CITATIONS • Refer to info in Appendix B • At least THREE sources: • At least ONE peer-reviewed journal (check with library) • Not including your lab manual (although you can ref this) • Anything from wikipedia or the web MUST be confirmed with another source

25. What to turn in • ROUGH DRAFT due next week • Bring Three copies of your rough draft • Make three copies of the peer review grading rubric and staple one copy of rough draft to one copy of grading rubric. • Deduction if this is not done as both are needed by your peer reviewer. • NEXT WEEK: Rough drafts will be distributed randomly for you to peer edit

26. Using the Spec • Read your samples • Prepare samples containing water, catechol and potato extract • Re-blank spec • Read absorbance for each sample

27. Part 2: Catecholase • Measuring color change with spectrophotometer – measures the amount of light that penetrates at different wavelengths

28. Product Formation Absorbance Part 2: Product Formation and Absorbance

29. Using the Spec • Zero the spec • Mix 1mL potato extract + 5mL dH2O in tube • Invert tube to mix and wipe clean so the spec can read it appropriately. • Follow the directions for using the spec (each may differ). You will need to zero it. • When the spec is ready, insert the tube (mark it so you insert it the same way every time) • Make sure the spec readings make sense; if something is off the readings are garbage