24 November 2014
Effect of Differing pH, Temperature, and Enzyme Concentration on Catalase Reaction Rate
Enzymes are used to increase the rate of specific reactions in the body. Catalase, a specific enzyme,
speeds the breakdown of hydrogen peroxide, a toxic chemical produced by cells in the body, into water and oxygen (Cain and others, 2010). The oxygen can be observed as bubbles coming from the reaction site. Catalase is found in many living tissues of organisms, including chicken liver. The purpose of this experiment is to determine what changes in pH, temperature, and enzyme concentration have on the rate catalase works to break down hydrogen peroxide. If the pH, temperature, or enzyme concentration changes, then the reaction rate of catalase will either speed up or slow down.
Materials and Procedures
Materials needed include 1 molar HCl solution, 1 molar NaOH solution, 6 test tubes, measuring
pipette, 10ml graduated cylinder, 40 ml 3% hydrogen peroxide solution, straightedged razor blade, scissors, forceps, stirring rod, fresh liver, fresh apple, fresh potato, test tube holders, ice bath, warm water bath, and boiling water bath.
Place 2 ml of the 3% hydrogen peroxide solution into a clean test tube. Using forceps and scissors,
cut a small piece of liver and add it to the test tube. Push it into the hydrogen peroxide with a stirring rod. Observe the bubbles. Assume this reaction is rated 4 on a scale of 05. This reaction is the control group for the experiment. The 05 scale based on bubbles is the measurement technique for each experiment. Pour off the liquid into a second test tube. This used liquid is the independent variable. Add more liver to this
liquid. Record the reaction rate. The reaction rate will be the dependent variable in each experiment. Add another 2 ml of hydrogen peroxide to the liver remaining in the first test tube. Record the reaction rate. B
Place 2 ml of hydrogen peroxide in each of 3 clean test tubes and then add each of the three test
substances (potato, apple, chicken) to the tubes. The three substances are the independent variables. As you add each test substance, record the reaction rate for each tube. C
Put a piece of liver into the bottom of a clean test tube and cover it with a small amount of water.
Place this test tube in a boiling water bath for 5 minutes. Remove the test tube from the hot water bath, allow it to air cool, then pour out the water. The fact that the liver was boiled is the independent variable. Add 2 ml of hydrogen peroxide. Use a testtube holder for hot test tubes. Record the reaction rate. Put equal quantities of liver into 2 clean test tubes and 1 ml H2O2 into 2 other test tubes. Put one test tube of liver and one of H2O2 into an ice bath. Place the other set in a warm water bath (not boiling). The temperature of each set of liver and peroxide is the independent variables. After 3 minutes, pour each tube of H2O2 into the corresponding tube of liver and observe the reaction. Record the reaction rate. D
Add 2 ml hydrogen peroxide to each of 5 clean test tubes. Add 4 drops of HCl to the first test tube, 1
drop HCl and 3 ml water to second, 4 drops NaOH to third, 1 drop NaOH and 3 ml water to fourth, and 3 drops water to fifth.The independent variable is pH of the solution added to each test tube. Add liver to each of the test tubes at the same time. Record the reaction rate of each tube.
Results,Data Collection, and Analysis
The H2O2 fully reacted with the catalase in the first experiment because it did not react anymore
when more catalase (liver) was added. However, the catalase was still present after the reaction because it converted additional H2O2 at the same reaction rate. The reaction rates of the three tests are in the following table:
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