Christopher Kim<br />Biology SL<br />October 16, 2009<br />Relationship Between Catalase and Peroxide<br />Introduction<br />Enzymes are proteins which are vital to our body because they are effective catalysts and they play an important part in reactions within our cells. Enzymes are specific; different enzymes only react with certain substrates which results in the lock and key model, where the shapes enzymes and substrates match with their corresponding half. An enzyme can be used over and over again until it is denatured, or until it changes shape which makes it unable to react with its specific substrate. The enzyme that will be tested in this experiment is catalase, which is essential in breaking down hydrogen peroxide, another important part of this investigation.<br />catalaseH2O2, commonly known as hydrogen peroxide, is a harmful substance that kills cells. Nonetheless, our body generates peroxide within each individual cell as a regular cellular function. So, in order to get rid of this toxic compound, our body has developed catalase to break down peroxide into water and oxygen. This can be shown by the following equation:<br />2 H2O2 -------------------- 2 H2O + 2 O2<br />This is a balanced equation with H2O being water and O2 being oxygen gas. So, catalase is the enzyme specific to peroxide, which breaks it down into harmless substances which prevents injury to our cells. This can be shown in the use of peroxide as an antiseptic used to clean cuts on skin. The peroxide bubbles and causes a decomposition reaction; it reacts with the catalase in our blood and releases oxygen gas. The oxygen gas is vital in dealing with certain bacteria which our immune system cannot kill. The release of O2 will result in a pressure change if the catalase was applied to the peroxide in an enclosed space, such as a tube. So, in this research, the rate of the pressure change will be measured to see how fast the catalase reacted with the peroxide, with the addition of PH.<br />Enzymes react more quickly or slowly when placed in different values of pH. pH is a measure of the acidity or alkalinity of a solution, which is determined by the ratio between OH- and H+ ions. Solutions with a pH greater than seven are basic, while solutions with a pH less then seven are considered acidic. Subsequently, in this experiment, hydrogen peroxide will be mixed with various levels of pH buffers, which then will be broken down by catalase to test how effectively our cells remove peroxide in our body. Thus, the pressure will signify whether the catalse reacted quickly or slowly than usual. According to prevalent scientific research, this concept has already been experimented, and the pressure changes are expected to form a bell curve when placed in a graph. An example of this is: <br />With the X-axis being the increasing values of pH starting from one, and the Y-axis being rate of enzyme activity. In conclusion, this investigation will be tested to research how catalase reacts with peroxide in different values of pH. This will help to see how catalase works within our body to remove hydrogen peroxide from our cells.<br />Design<br />Research Question<br />What is the relationship between peroxide and catalase when placed in different amounts of PH solution?<br />Variables<br />Independent variable: the amount of catalase and peroxide<br />Dependent variable: the pressure of the oxygen after the catalase has reacted with the peroxide<br />Controlled variables: The size of the tubes were controlled by using the same sized test tubes for the experiment. The volume of the solution was controlled by using the same amount of solution for the test tubes. The temperature was controlled by conducting the experiment in the same room. The procedure was controlled by using the same method for the enzymatic reactions in the investigation.<br />Materials<br /><ul><li>Laptop
Pour the solutions into the separate catalase tubes.
As soon as all the solution has been poured in the test tube, put the stopper on to measure the rate.
Use the logger pro functions to find the slope of the rates.
Rinse and repeat for each tube.</li></ul>Data Collection and Processing<br />Table 1: Rates of pressure derived from the release of oxygen<br />Kpa/s (±0.1)<br />pHTrial 1Trial 2Trial 3Trial 4Trial 518.104.22.168.53.153.01.62.53.12.322.214.171.124.15.8126.96.36.199.12.4188.8.131.52.15.8<br />Table 1: This table shows 5 trials held for values of 3, 5, 7, 9, and 11 of pH. Uncertainties of the kpa/s were found by measuring the instrumental limitations of the logger pro program.<br />Sample Calculations<br />First, the averages of the 5 trials for each different value of pH were measured in order to determine the mean of the rates of pressure.<br />Calculation of Rate<br />The values for the 5 trials of each pH was added then divided by 5 to find the average rate. The results yield the formation of this table shown below.<br /><ul><li>Rate of reaction
=2.2</li></ul>Table 2: The rate of the reaction found by calculating the mean of the 5 trials.<br />pHRate of reaction32.2 (±0.8)52.5 (±0.8)73.9 (±2.1)94.8 (±2.0)114.7 (±1.9)<br />Uncertainties<br />The uncertainties for the rates were found by dividing the range of the 5 trials by 2 for each number of pH. The range is the largest number out of the 5 trials subtracted by the least number.<br /><ul><li>Uncertainty of rate
= 0.8</li></ul>Rate of reaction vs. pHGraph 1:<br />Graph 1: The graph above shows the different rates of reaction for pH levels of 3, 5, 7, 9, and 11. The vertical lines determine the uncertainties of the rates of reaction.<br />Qualitative Observation<br />pHObervation3When contacted with the catalase, the hydrogen peroxide bubbled. Solution turned milky white.5Solution bubbled. Bubbled nearly reached the top of the tube. Solution turned white.7Considerably fast reaction. Solution almost spilled out of the tube. Solution turned milky white.9Solution bubbled. Bubbles reached the top of the test tube. Solution turned milky white.11Solution bubbled. Solution turned white.<br />Conclusion<br />The graph somewhat supports the hypothesis presented in the introduction. The rates do increase in the beginning, but continues to rise after the pH of 9. This is inconsistent with how catalase works because the enzyme denatures in solutions above a pH of 7. <br />This experiment was conducted within a range of pH 3 to pH of 11, so this investigation is valid. However, beyond this pH range, it is unknown whether the hypothesis will remain constant.<br />Evaluation<br />Even though the experiment was performed carefully to minimize errors, there were still errors which may have changed the results.<br />The main weakness of the investigation was the method.<br />Second, one of the limitations was in the unreliability of the pressure meters. Screwing the caps on too lightly or too tightly resulted in different results than what was expected. Also, some pressure meters were old, meaning that their reliability dropped even further. <br />