Effects of Enzyme Catalysis of H2O2 by Catalase

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Effects of Enzyme Catalysis of H2O2 by Catalase

Report by: Timmy Lin (#269164729)
October 17, 2011
Mr. Rienzi AP Biology

Problem: Measuring the effects of Catalase enzymes on hydrogen peroxide decomposition. Measuring the rate of the reaction when hydrogen peroxide and Catalase are mixed at the same ratio for different time (10, 20 30 60 120 180 360 seconds).

Background: Enzymes are biological catalysts that carry out cellular metabolic processes with the ability to enhance the rate of reaction between. They are large proteins made up of several hundred chains of amino acid. In an enzyme-catalyzed reaction, the substance to be acted upon, or substrate, binds to the active site of the enzyme. The enzyme and substrate are held together in an enzyme-substrate complex by hydrophobic bonds, hydrogen bonds, and ionic bonds. Often, enzymes are multi-protein complexes made up of a number of individual protein subunits. Hydrogen peroxide in lower concentrations, such as the types found in many homes, it works well as a disinfectant and antiseptic. Another use for hydrogen peroxide is to purify water. It is highly soluble in water, and adding it to water can increase oxygen and help eliminate dangerous contaminants. It is also used in some swimming pools in place of other water purifiers. Hydrogen peroxide is a colorless liquid that goes through the following spontaneous decomposition reaction. 2H2O2 2H2O + O2

This is a spontaneous reaction meaning it requires no energy to begin down but the reaction itself takes a long time. The enzymes lower the activation energy of the reaction allowing the reaction is occur at much faster rate allowing us to see the oxygen bubbles that are formed as a product of the reaction. The enzyme does this with the use of substrate conversion within the active site. The solution is then left there for a certain amount of time before it is denaturized. The denaturalization of enzyme can be done in many different ways; we stopped the reaction with the addition of Sulfuric Acid (H2SO4). The change in pH alters the enzymes quaternary structure and alters the active site so that it cannot accept H2O2 a substrate and ends catalysis. Other methods in the denaturalization of enzymes include altering salt concentration and temperature. Hypothesis: If I leave the hydrogen peroxide with the catalase for a longer period of time, then the reaction rate will remain the same.

Two 10 mL Pipettes
Eight 50 mL Beakers
2% KMnO4
Three 5mL Pipettes
1M H2SO4
Two 100 mL Beakers
1.5% H2O2
Potato (boiled and nonboiled)

Establishing a Baseline
1. Place 10 mL of 1.5% H2O2 into a clean 50mL beaker. Be sure to use a pipette to get the most accurate reading for the amount of H2O2. 2. Now using a new pipette, that isn't contaminated, place 1 mL of H2O into the 10ml of 1.5% H2O2. 3. Using a new pipette, place H2SO4 into the solution of H2O2 and H2O. Be very careful when using H2SO4; always wear goggles throughout the whole lab to ensure the safety of your eyes. 4. Now mix well using a clean mixing stick.

5. Using a new pipette remove a 5 mL sample of the solution we created. Place the 5 mL solution in a clean beaker. Now place a white sheet of paper behind the beaker. 6. Using a new pipette place 5 mL of KMnO4, one drop at a time, into the 5 mL solution. Swirl the solution until the solution becomes pink or brown. 7. Measure the amount of KMnO4 left in the pipette. Record the amount of KMnO4 left in the pipette and subtract it from the original to get the baseline.

The Uncatalyzed Rate of H2O2 Decomposition
1. Place 15 mL of H2O2 into a 50 mL beaker and store it in room temperature uncovered over night for 24Hr 2. Repeat steps 2-7 from Establishing Baseline
Time Course Determination
1. Place 10 mL of 1.5% H2O2 into a clean 50mL beaker. Be sure to use a pipette to get the most accurate reading for the amount of H2O2. 2. Now...
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