Biology Lab: Enzyme Catalysis

Concept: Enzymes are proteins that assist metabolic reactions and enable them to take place at lower temperatures or higher rates, as required by different circumstances. The presence, concentration, or absence of enzymes can determine the rate at which a reaction occurs — or whether it occurs at all. Enzymes can be denatured or rendered ineffective by temperature changes or interactions with acids and bases.

Goal: To observe the effects of acidic inhibitions of catalase activity.

Alternative Experiment #1

Perform Illustrated Guide to Home Biology Experiments, Lab III-3, Procedures 1 and 2 (we will do measurements of Vitamin C in another lab).

Alternative Experiment #2

Perform the Catalase Lab designed by Gen Nelson at Access Excellence, which has instructions on how to make your own catalase solution from potatoes. You may also find the instructions for the Flinn Scientific version of the this experiment useful in planning your procedure. If you prefer commercial catalase, it is available from several suppliers on my science supplies list.

Pay particular attention to all safety instructions!

The lab contains a method for preparing a catalase extract from potatoes, as an alternative to commercial catalase. Also, instead of using potassium permanganate to measure the presence of H₂O₂, the lab uses a "floating filter" measure of O₂ production, which is, of course, proportional to the disappearance of hydrogen peroxide.

You can skip the section on the effects of pH on enzyme activity, OR use the following substitutes for the pH variations. To make solutions from baking soda and cream of tartar, put 1 tsp. in 1/4 C distilled water and dissolve completely.

Alternative Experiment #3

If you cannot manage to work through the Access Excellence lab, then work the Enzyme Activity Simulation lab and record your data for enzyme activity for maltase and amylase as they break down starch and maltose to glucose.

1. Set the starch to 2.5, the amylase and maltose to 1, and the glucose, and amyl,ase inhibitor amounts to 0.
2. Set the pH to 7.
3. Set the temperature to 35°.
4. Perform a run (click "Run Simulation").
5. Pause the simulation when the amounts for starch, maltose, and glucose stop changing and record the time necessary for starch and maltose to reach 0. What happens to glucose?
6. Reset the experiment and change the temperature to 40F and rerun the experiment. Record the amount of time necessary for starch and maltose to reach 0. What happens to glucose?
7. Reset the experiment and change the temperature to 45F, and then repeat at 50F. Record your observations. How does temperature affect the activity of the enzyme?
8. Reset the experiment and set the temperature to 40F. Then rerun the experiment four times, with the pH set to 2, 5, 9, and 12. How does pH affect enzyme activity?
9. If you have time, rerun the experiment with temperature at 40F, amylase and maltose at 2, and vary the amylase inhibitor for three runs, using 1, 3, and 5. How does the inhibitor affect the activity of the enzymes?

Report

Fill out the lab report data tables and answer the questions for the lab you perform (AP, IGHBE, or Access Excellence). Leave any columns for class averages blank; we will do those together.

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