Web Lab on Enzymes: Teacher Guide

Original Document: Web Lab on Enzymes

Go to: http://bioweb.wku.edu/courses/Biol114/enzyme/enzyme1.asp

Part I - Measuring the Rate of Reaction


1. Write the equation for the reaction that the enzyme catalase carries out. reaction

2. Why does raising the temperature increase the rate of the reaction? increases the movement of molecules and the chance the enzyme and substrate will bump into each other
3. What can be used to STOP the reaction of catalase? Why does this work. Using sulfuric acid lowers the pH to a level that catalase no longer functions

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4. What is the active site? _________place where the substrate fits into the enzyme______________________
5. If we start with 3 ml of H2O2 from your bathroom cabinet and add catalase. After 3 minutes we measure the amount of H202 remaining and find 1 ml remains.
How much H202 was consumed in the reaction? _____2 ml_____
6. If we repeated the experiment above but found 2 ml of H202 remaining,
would this indicate a lower or higher rate of reaction? _____lower rate of reaction, less was broken down____________

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7. The Experimental Procedure - fill in the blanks
____Incubate____ tubes containing catalase and __hydrogen peroxide__ at different temperatures and examine the rate of enzyme activity by _____titrating________ any remaining (unreacted) substrate. This will give us an indirect measure of the substrate converted to ___product_________ and therefore the ____rate_________ of reaction.

8. When you added H2O2 to the test tubes you added substrate or enzyme? _____substrate
9. The four tubes are placed in what temperatures? ___4, 24, 34, 44__
10. After you added catalase, wait 3 minutes and then add what? ____acid___ Why is this step important? stops reaction
11. What reaction occurred in the test tubes? catalase + H2O2 --> O2 and H2O
12. Titrate using potassium permanganate each of the four tubes and fill out the table below.

  Tube 1 (4) Tube 2 (24) Tube 3 (34) Tube 4 (44)
Amount of Potassium Permanganate needed
7 3 2 9

13. (Click on "back to the lab") Which tube had the highest rate of reaction? How do you know?
_____tube 4 used the most KmNO4, which means it had the most peroxide left, it had the slowest reaction, tube 3 had the least amount of kmno4 needed to react, therefore it had the least amount of peroxide left and the fastest reaction__________
14. What variable(s) would have caused the differences in reaction rates for each tube? _____temperature was the only variable that was changed, or temp and time

Part II - Extension Questions (not on site):

15. Amylase is an enzyme in saliva that helps to break starches into sugars. An experiment with amylase and starch was set up similar to the one you did above and the following results were obtained. Instead of measuring the amount of starch remaining in the tube, scientists measured the amount of glucose produced. Assume that the temperature was never raised high enough to denature the enzyme.

Which of the tubes in the above experiment was the coldest? __tube 4 __ The warmest? ___tube 1____
Explain how you know this. _______Tube 1 had the least amount of glucose left in it, fast reaction = warm temp________________

16. Indicators such as potassium permanganate and iodine can be used to measure the amount of substance left in a test tube or beaker. For each of the indicators, list whether they serve to indicate substrate left, or product created.

Iodine measure the amount of starch broken down to glucose ____product created_________
Potassium permanganate measure the amount of peroxide in a beaker _substrate left________