| Enzyme Rate of Catalase |
Introduction:
Enzymes are molecular substances found in cells. Enzymes act as catalysts and most are proteins. Enzymes bind temporarily to one or more of the reactants of the reaction they catalyze. In doing so, they lower the amount of activation energy needed and thus speed up the reaction.
Not only do enzymes economize energy usage, but also provide a variety of other functions. Cells uses an enzyme (catalase) to rid itself of a poisonous substance (hydrogen peroxide). The rate at which this occurs depends on the amount of catalase that is available. In this lab we are going to measure the time it takes for a disc of filter paper, soaked with different concentrations of enzyme, to make its way to the top of a plastic vial filled with peroxide. Rate of enzyme activity = distance (depth of hydrogen peroxide in mm)/time (in sec).
Catalase catalyzes the decomposition of hydrogen peroxide into water and oxygen. One molecule of catalase can break 40 million molecules of hydrogen peroxide each second.
catalase
2H2O2 —–> 2H2O + O2
Objectives:
| Students will prepare various dilute solutions from a 100% enzyme solution. |
| Students will determine how enzyme concentration affects reaction rate. |
Materials:
6 medicine cups for dilutions, *catalase stock solution, clear plastic vial, forceps, 18 filter paper disks, Hydrogen Peroxide (H2O2), paper towel, apron, safety glasses, watch with second hand, marker, metric ruler, calculator
* The enzyme has been prepared for you as follows: 50g of peeled potato was mixed with 50 ml cold distilled water and crushed ice and homogenized in a blender for 30 seconds. This extract was filtered through cheesecloth and cold distilled water was added to a total volume of 100 ml. Extract concentration is arbitrarily set at 100 units/ml. ENZYME SHOULD BE KEPT ON ICE AT ALL TIMES!!
Procedure:
- Make a series of dilutions of the enzyme catalase using the following table.
| Final Quantity Needed | Concentration of Final Solution | mL of Catalase | mL of Water |
| 10 ml | 100% | c10 | 0 |
| 10 ml | 80% | 8 | 2 |
| 10 ml | 60% | 6 | 4 |
| 10 ml | 40% | 4 | 6 |
| 10 ml | 20% | 2 | 8 |
| 10 ml | 0% | 0 | 10 |
- Use a marking pencil and mark the enzyme solutions as follows: 100%, 80%, 60%, 40%, 20%, and 0%.
- Fill a clear vial with 20 mL of hydrogen peroxide.
- Using your forceps, pick up one filter paper disk and submerge it in the 100% enzyme solution for 5 seconds. Continue to hold the disk with the forceps.
- Using your forceps, pick up one filter paper disk and submerge it in the 100% enzyme solution for 5 seconds. Continue to hold the disk with the forceps.
- Remove the disk from the solution and blot it dry, for five seconds, using your paper towel.
- Drop the disk in the hydrogen peroxide and measure the time it takes for the disk to rise up from the bottom. Begin timing as soon as the disk touches the surface of the hydrogen peroxide.
- Use the metric ruler to measure the distance the disk sinks into the hydrogen peroxide. multiply by two to determine the entire distance the disk traveled. Enter the time and distance the disk traveled in the column for Trial 1 in the data table below.
| % Catalase | Time in seconds | Distance in millimeters | Reaction Rate mm/s | ||||||
| Trial 1 | Trial 2 | Trial 3 | Avg. | Trial 1 | Trial 2 | Trial 3 | Avg. | ||
| 100 | |||||||||
| 80 | |||||||||
| 60 | |||||||||
| 40 | |||||||||
| 20 | |||||||||
| 0 | |||||||||
- Repeat the above steps for the remainder of the solutions. Remember to use clean filter paper each time you use a different solution. Enter the times and distances for trial 2 and 3 in their appropriate columns.
Analysis & Conclusion:
1. Which concentration of catalase had the fastest reaction time?
2. Which concentration of catalase had the slowest reaction time?
3. What is catalase & why is it important to cells in your body?
4. How did you know that catalase was present in the above compounds?
5. What 2 substances form when catalase breaks down hydrogen peroxide?
6. What type of organic compound is catalase?
7. Produce a line graph of the above data. Use the enzyme concentration as the independent variable and the reaction rate as the dependent variable.
Graph Title:__________________________________________________
Legend:
8. Based on the graph and overall slope of the line, what can you conclude about the effect of enzyme concentration on reaction rate?