Science in Motion-UrsinusCollege

Catalase Lab- Teacher notes

Preparing the catalase

About 10 minutes before the class get a 250ml beaker and add 100ml of warm water. Add one scintillation vial of sugar. Add one package of yeast and stir. You should make fresh catalase for each class.

Using the macropipettes

You will not have to change tips at the student stations because they are just adding hydrogen peroxide and water to their test tubes. You should use a separate pipette at each pH station to avoid having to change tips. Please rinse and return tips at the end of the lab.

Lab results.

Concentration

Students should get a series of lines on their graph with increasing slope linked to the number of drops of catalase. If done correctly, the lines should be fairly evenly spaced. Often students are not careful in counting drops or have drops land on the side of the test tube which will effect results. If a drop of catalase lands on the side of the test tube, have students tilt the tube so that it mixes with the water and hydrogen peroxide.

ph

Each enzymes has a range of pH in which it works best. Students should find that a ph of 4 is too acedic for this enzyme. It will work in a ph of 10 or 7.

Temperature

Students are testing three temperatures. For 0-5 student should use a mixture of ice in water. For room temperature no water bath is necessary. For the 60-65 C, a hot plate is necessary to start the water bath. If it has a temperature adjustment, the bath can be left on the hot plate. If there is no adjustment, the bath will have to be taken off the hot plate before the test is run. This is the hardest part of the lab for students to get good results on because it takes excellent lab technique. To get correct results, students must have the contents of the test tube and the water bath at the same temperature before they run the test. If for instance, if the test tube is 64 degrees but the water bath is 75 degrees, the pressure in the tube will increase as the tube warms up because the air in the tube will expand as it is heated. To see the result of just the enzyme, the temperature of the tube must remain stable.

In this test, students should see the best results for the enzyme at room temperature. The enzyme works poorly in cold temperatures and it also works poorly in hot temperatures because the heat denatures the enzyme.