The following FAQ contains frequently asked questions and answers about the "Enzyme-Catalyzed Reactions -- What Affects Their Rates?" project. If you are having trouble with the procedure, you may find assistance in the answers below.Q: Do I need to put the catalase solution on ice?A:
Yes, you must keep the catalase solution surrounded by ice. The activity of the catalase enzyme in the solution decreases over time. Keeping the solution on ice makes the enzyme's activity decrease more slowly, giving you more time to do the experiment. If it is kept on ice, the solution should remain very active for 2 to 3 hours. Q: The coffee filter ripped while I was filtering the catalase solution and unfiltered solid material fell into the jar. What should I do?A:
Take a clean beaker or jar, put a new coffee filter in place, and re-filter the catalase solution into the new container. Using a funnel to support the coffee filter may prevent the filter from tearing.Q: Ice fell into my catalase solution. What should I do?A:
This is not a major problem. Simply remove the ice from the solution before it melts. If you have problems with ice falling into your catalase solution or hydrogen peroxide containers, then put lids on those jars.Q: My results are not what I expected—near the end of my experiment the filter paper took a lot more time or less time to rise than I expected. Did I do something wrong?A:
If you feel that your results do not make sense (or if a graph of your data does not show a clear trend), the problem may be that your catalase solution was too old by the end of your experiment. Keeping the catalase solution on ice slows
the enzyme's decrease in activity, but it does not stop it completely. After two or three hours, the enzyme's activity will have decreased so much that it may make your results confusing because, overall, the filter paper will take longer to rise in the experiments you did at the end.
To fix this problem, redo the experiment with fresh catalase solution. Use the catalase solution as soon as you make it. If the experiment takes more than 2 hours, stop and make a new catalase solution and use it to finish the experiment. Running multiple tests at once will help you finish the experiment faster, but if you choose to run multiple tests at the same time, make sure you do not get them mixed up!
Another, more advanced, option would be to do the different temperatures in each of the three trials in a different order (e.g., cold to hot, hot to cold, etc.). This helps "spread out" the effects of decreasing enzyme activity. Q: How can you tell when the filter paper is back to the top of the hydrogen peroxide? A:
It can be a bit tricky to tell exactly when the filter paper floats back to the top of the hydrogen peroxide. If you are having trouble seeing this, try watching the filter paper from the side, with the top of the hydrogen peroxide at eye level. When the filter paper begins to rise, pay close attention to it. Use your best judgment to decide when the filter paper reaches the top of the hydrogen peroxide. The most important thing is to be consistent with each test that you run. Q: The filter paper is not rising. What should I do? A:
First, wait a few minutes. The filter paper can take a few minutes to begin to rise. If it has not risen after 5 minutes, then your catalase solution may have become inactive, especially if it is more than 2 or 3 hours old. If the solution has not been kept on ice, it may become inactive within a shorter period of time.
If it has been more than 2 hours since you made the catalase solution, make a new catalase solution and continue the experiment. If you have already run a complete test of all temperatures, it is probably okay to use that data. But, if you have an incomplete set of data (you have not done all of the different temperatures), you may want to only use data you collected in the first 2 hours and re-run all of the later tests in that set. Make sure to write down everything you do in your lab notebook.
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