Biology Filter Paper Catalase Enzyme Lab SL Experiment IA...
Testing for Catalase Enzyme Activity with Filter Paper Disks Introduction Hydrogen peroxide (H2O2) is a poisonous byproduct of metabolism that can damage cells if it is not removed. Catalase is an enzyme that speeds up the breakdown of hydrogen peroxide into water (H2O) and oxygen gas (O2). Catalase enzyme 2H202 2H2O + O2 A CATALYST is a substance that increases the rate of the reaction without being used up in the process. CATALASE is an enzyme, a biological (organic) catalyst. Hydrogen peroxide is the substrate for catalase.
Methods The assay system used in this lab consists of a filter paper disc which is coated with the enzyme and then dropped into a vial (microtiter plate*) of substrate (hydrogen peroxide). As the enzyme breaks down the hydrogen peroxide into water and oxygen gas, the bubbles of oxygen collect underneath the filter disc and make it rise to the surface of the hydrogen peroxide. The time it takes for the filter disc to rise is an indication of the rate of enzyme activity. You will be doing 5 repetitions for each experiment. Rate: Rate of enzyme activity = distance (depth of hydrogen peroxide in mm)/time (in sec). We will assume that each filter is coated with the same amount of catalase (except in the investigation of the effect of enzyme concentration on enzyme activity).
Enzyme: The catalase enzyme has been prepared for you as follows: 50g of peeled potato was mixed with 50 ml cold water and crushed ice and homogenized in a blender for 30 seconds. This extract was filtered through cheesecloth and cold 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!! Question #1: What is the effect of enzyme concentration on rate of reaction? 1. Make a large number of filter paper discs using a coffee filter and a hole punch. 2. Measure the depth of one sample vial on the microtiter plate. (This will be needed in order to determine rate). 3. Obtain approximately 100 ml of 3% hydrogen peroxide in a beaker. 4. Fill 5 vials, on microtiter plate, with 3% hydrogen peroxide (substrate). Set the plate aside. 5. Obtain 5 plastic cups and label with the enzyme dilutions listed in table 1. Table 1 Enzyme Concentrations Enzyme Dilutions Enzyme 100 units/ml 20 ml 75 units/ml 15 ml 50 units/ml 10 ml 25 units/ml 5 ml 0 units/ml 0 ml 6.
Cold dH20 0 ml 5 ml 10 ml 15 ml 20 ml
Set up a cold water bath and obtain about 50 ml of enzyme stock solution in a plastic vial. KEEP YOUR STOCK SOLUTION IN THE COLD WATER BATH AT ALL TIMES!
9. 10. 11.
Set up your first enzyme concentration (100 units/ml) in the appropriate plastic cup. Only make one enzyme dilution at a time, this will keep your stock solution in the cold water bath as long as possible. (Check the temperature and make sure to keep it constant throughout the investigation.) Using forceps, dip a filter disc into the enzyme solution at 100 units/ml, remove it and drain it by touching it to the edge of the cup. Drop the disc into the vial of hydrogen peroxide labeled 100 units/ml and time how long it takes the filter to rise to the surface. Repeat this process five times for the each individual enzyme dilution. Make sure you keep track of the start and stop times for EACH vial. Use a FRESH set of vials of substrate for each filter paper disc. Record your results in an appropriate data table. Repeat steps 7-9 for each of the other enzyme dilutions, be sure to use a FRESH set of vials of substrate for each filter paper disc. Clean your materials including plastic cups for the second half of the lab.
Question #2: What is the effect of substrate concentration on the rate of reaction? 1. Label your plastic cups with the substrate dilutions listed in table 2. 2. Use your remaining hydrogen peroxide (get more if necessary) and set up the five dilutions listed in table 2. Each dilution should be made in a separate, labeled plastic cup. Table 2 Substrate concentrations Hydrogen Peroxide Dilutions 3.0% H2O2 2.25% H2O2 1.5% H2O2 0.75% H2O2 0.0% H2O2
H2O2 20 ml 15 ml 10 ml 5 ml 0 ml
dH20 0 ml 5 ml 10 ml 15 ml 20 ml
3. Check and record the temperature of the remaining stock enzyme solution. (Make sure to keep the temperature constant throughout the investigation.) 4. Fill 5 vials, on microtiter plate, with the 3.0% dilution of hydrogen peroxide (substrate). 5. Stir or shake your enzyme to mix the contents. Using forceps, dip a filter into the enzyme solution and drain it by touching it to the edge of the cup. Drop the filter into the vial of H2O2. Time how long it takes the filter to rise to the surface. Repeat this process five times for each individual substrate dilution. 6. Repeat step 5 for each of the substrate dilutions, be sure to use a FRESH set of vials of substrate for each filter paper disc. 7. Record your results in an appropriate data table. * Microtiter Plate – microplate is a flat plate with multiple "vials" used as small test tubes.