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I want to find out if the concentration of the Hydrogen Peroxide affects the speed at which the potato gives off gas.

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Catalase Investigation Aim: * I want to find out if the concentration of the Hydrogen Peroxide affects the speed at which the potato gives off gas. Planning Enzymes like catalase are protein molecules that are found in living cells. They are used to speed up reactions within the cell, and so are biological catalysts. Catalysts speed up reactions but they are not changed during the reaction. Enzymes only work on one specific type of substrate that means that there is only one kind of substrate that will fit into the enzyme's active site. Most enzymes optimum working temperature is 37�C (body temperature). Catalase is found in food such as potato that I will be using in my experiment. They are all very specific as each enzyme is used for different jobs. Catalase is used for removing Hydrogen Peroxide from the cells. Catalase is used to speed up the decomposition of the Hydrogen peroxide into water and oxygen. Preliminary experiment First of all I did a preliminary experiment, when we picked 15 potato chips at random and cut them down to the same length using a razor blade, making them even. I then set up the equipment as shown below and injected the hydrogen peroxide solution, and timed how long it took for 1ml of gas to be displaced as the H2O2 is attacked by the enzymes in the potato. ...read more.


3: Accurate amount of solution: More solution may affect the rate of reaction. To make the amount of solution placed in the test tube as accurate as possible a syringe will be used to measure out the exact amount needed. 4: Contamination: As each test tube is filled up with the different strength solutions the syringe which would measure the amount of solution placed in the test tube may become contaminated with different concentrations. To stop this the syringe must be washed every time they are used. 5: Average: To make the experiment as accurate as possible an average will be taken out of 3 results taken. Also any clearly anomalous results will be ignored. 6:Temperature: The temperature may affect the reliability of the experiment for example at extreme temperatures the cells of the potato may die and at less extreme temperatures the experiment may be speeded up. To keep this from happening all the time the experiment will happen at room temperature. Prediction: I think that the less concentrated the solution of H2O2 is, the longer it will take for 5ml of gas to be given off because there won't be as many H2O2 molecules to collide with the catalyse on the potato, so it'll take longer for the reaction to take place. ...read more.


These were probably due to reading errors or slight changes in the potato type used. Another possibility is that one sample may have contained more potato skin than the others. The skin may be a faster or slower working enzyme than the potato flesh. The other factor that may have affected the experiment is the accidental release of oxygen bubbles or samples of either substance. I could have ensured more accurate results by using more accurate equipment, such as a more exact ruler or a micrometer, or the measuring cylinder that would have been more accurate had been a lot thinner (a burette). There was sufficient evidence from the testing I carried out to support my conclusion because the results I obtained were enough to agree with my original prediction. I could have continued testing different variables, which would have proved or disproved my prediction correct. Further work to reach a better conclusion may be to research into more scientific theories and carry out experiments repeatedly until an accurate set of averages is achieved. If all the independent variables were experimented with as dependant variables then a nearly perfect conclusion could be drawn. I think that my method for finding how the concentration of catalase affects the rate of the reaction between catalase and hydrogen peroxide was the best possible one under school laboratory conditions. Philip Singer, 11W1 Biology Coursework - 1 - ...read more.

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