By: Marie, Jacob, Jenna, Max, and Nikita The Effect of Different Levels of pH on the Rate at which Catalase Decomposes into Water and Oxygen By: Marie, Jacob, Jenna, Max, and Nikita

Abstract

Background Enzymes work at a certain pH Enzymes designed to work in their natural environment Examples: Pepsin works in stomach in highly acidic conditions therefore has optimal pH of 2 Pancreatic amylase is active in neutral conditions of the small intestines, having an optimal pH of around 7.0 Can make fairly safe assumption of other enzymes' optimal pHs.

Hypothesis Our hypothesis states: The higher the number falls on the pH scale, or the more basic it is, the quicker the reaction of the catalase in relation to the hydrogen peroxide should occur.

Independent variable Dependent variable Variables pH levels pH3 pH7 Gas pressure

Materials Vernier Gas Pressure Sensor Tubing rubber with Luer-lock connectors (provided with gas pressure sensor) Computer with Internet access and Vernier LoggerPro® software 20-200 µL micropippetor (or transfer pipettes) LabQuest Mini 200 µL micropipette tips 125 mL Erlenmeyer Flask Catalase solution, 200units/mL Magnetic stirrer 3% Hydrogen Peroxide Stirring bar pH 3 Ring stand pH 7 Utility clamp pH 9 Two-hole stopper assembly (provided with gas pressure sensor)

Method Obtain a Gas Pressure sensor, a LabQuest Mini, a ring stand, 125mL flask, and a magnetic stir plate. Measure out 50 mL of the pH 3 and peroxide solution into a 125 mL Flask Carefully place a stir bar in the flask Start Logger Pro® software on your computer. Place a magnetic stirrer on the base of a ring stand. Use a clamp to fasten the flask to the ring stand. Position the flask at the center of the magnetic stirrer. Connect the LabQuest Mini to the computer using the USB cable. Connect the Gas Pressure Sensor to CH 1 of the LabQuest Mini. Mix 50 mL of pH 3 with 50 mL of 3% hydrogen peroxide and put into container.

Method Using a micropipette, add 100 µL of the 200 units/mL catalase solution to the contents of the flask. Repeat steps 5–12 substituting pH 7 and pH 9 for pH 3. We used 2000 units/mL of catalase for pH 9. Tightly seal the flask by twisting in the two-hole stopper connected to the Gas Pressure Sensor. Ensure that the flask is properly positioned. Turn the stirrer on to the predetermined setting. Start data collection.

Results Catalase and Hydrogen Peroxide No pH was added so it could be used as the baseline. The graph continued to slightly increase throughout the two hundred seconds of the trail.

Results Catalase, Hydrogen Peroxide, and pH3 The level pH3 did not assist in the catlyzation of the peroxide. Instead it decreased throughout the trail.

Results Catalase, Peroxide and pH9 The amount of catalyzation was infrequent. It was non-reactant until one hundred and ten seconds. The catalyzation increased to a spike and the began to decreased.

Results Catalase, Hydrogen, and pH7 Catalyzation continued to increase throughout the two hundred seconds just as did the baseline. The optimal level of pH is pH7.

Discussion

Conclusion The optimal reaction rate did not occur with a higher pH level, but rather with a pH of 7, a neutral pH level.