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 We set out to find the optimal pH range in which the enzyme catalase will catalyze with Hydrogen Peroxide. This was measured by how much O2 was released, as the catalyzation of Hydrogen Peroxide and Catalase produce H2O and O2. The addition of the independent variable, pH, was instituted in order to find which pH will allow the enzymes to produce the most end products. This was done by combining a specific pH buffer with Hydrogen Peroxide, and then adding 200ml of catalase in an Erlenmeyer flask, connected to a gas pressure sensor to moniter the output rate. We found that the optimal pH was 7, as it had the highest rate of production for the longest amount of time. We conclude that the enzyme catalase catalyzes best with Hydrogen Peroxide at a neutral pH, specifically one of 7.

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(Worthington, 1) Pancreatic amylase is active in neutral conditions of the small intestines, having an optimal pH of around 7.0 (US Peroxide, 2) Can make fairly safe assumption of other enzymes' optimal pHs.

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.

Variables Independent variable Dependent variable pH levels pH3 pH7 Gas pressure (The result of the O2 being produced from the catalyzation)

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 The Results indicate an optimal pH of 7. Due to human error, this result may be faulty, however previous research supports our findings regardless. A mistake we made was putting 2000 ml of catalse when performing the pH 9 experiment Several of the human error problems could be solved by using better judgment and more careful measuring tools Further work to be done would be to use combinations of factors such as temperature and concentration in addition to pH.

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

Citations "What Is the PH of H2O2 Solutions?" Technologies for a Cleaner Enviornment. US Peroxide, 21 Oct. 2009. Web. 22 Jan. 2015. <http://www.h2o2.com/faqs/FaqDetail.aspx?fId=26>. "Introduction to Enzymes." Worthington: Biochemical Corporation. Worthington. Web. 22 Jan. 2015. <http://www.worthington- biochem.com/introbiochem/effectsph.html>.