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Aim This investigation aims to find out how anincrease in the concentration of hydrogen peroxide af

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Aim This investigation aims to find out how an increase in the concentration of hydrogen peroxide affects the rate at which catalase breaks it down. Introduction Hydrogen peroxide is a dangerous compound formed when oxygen runs into carrier molecules that shuttle electrons to and from sites within our cells. We get these carrier molecules from essential minerals such as riboflavin and niacin. Hydrogen peroxide can attack metal ions and sulphur atoms present in protein. To stop the dangerous actions of this compound, our cells make an enzyme called catalase which converts hydrogen peroxide into water and oxygen. Catalase molecules break down hydrogen peroxide molecules at a very fast rate which is essential to keep the level of hydrogen peroxide at a safe level. The catalase molecules in our body use an iron ion to assist this reaction which is gripped at the centre of a disk-shaped heme group. The enzyme is composed of four identical subunits, each with its own active site buried deep inside. Catalase performs its rapid destruction of hydrogen peroxide in two steps. First, a molecule of hydrogen peroxide binds and is broken apart. One oxygen atom is extracted and attached to the iron atom, and the rest is released as harmless water. Then, a second hydrogen peroxide molecule binds. It is also broken apart and the pieces are combined with the iron-bound oxygen atom, releasing water and oxygen gas. This is the equation of the reaction that occurs when catalase breaks down hydrogen peroxide: 2H2O2 catalase 2H2O + O2. Since they must break down reactive molecules, catalases are unusually stable enzymes. ...read more.


This diagram shows a rough layout of the apparatus. Step 2- Gathering reactants Place the boat on the electronic scale and press 'on tare' or 'on zero' depending on the scale. This will make the reading say 0.00. Then weigh out approximately 2 grams of grated carrot and place it in a boiling tube. Use the splint to push the carrot down to the bottom of the tube. Put the boiling tube in a test tube rack. Repeat this procedure to obtain 5 boiling tubes of carrot. Measure 2cm� of hydrogen peroxide at the concentration intended to take readings using the syringe. Now secure a rubber bung to the end of the delivery tube (if not attached) and place the other end into the beaker and secure it into the gas burette. The end of the delivery tube with the bung should be used to seal the boiling tube when the hydrogen peroxide is added to the carrot. The stop clock should be started immediately. Step 3- Taking readings When one minute has elapsed, remove the bung from the top of the boiling tube and record the volume of gas collected. Then measure 2cm� of hydrogen peroxide of a different concentration and add it to the next boiling tube with carrot and seal it with the bung. Start the stop clock immediately. Only take readings after one minute and when the volume of gas collected goes beyond 45ml, refill the gas burette with water so more gas can be collected. Step 4- Repeats Repeat the whole experiment so that two readings for each concentration are obtained. ...read more.


To prohibit this happening, I started to remove the bung 2 seconds earlier so that the time was kept constant each time. Concerns also arise as to whether or not there was any trapped air or gas in the delivery tubes. To improve my investigation, I could do a number of things. These include: 1. Extending the concentration of hydrogen peroxide used by increasing the concentration by 1.5% each time. This will increase the range of concentrations and could show the optimum concentration required for catalase to work at its maximum rate. 2. Having a control experiment. This could be achieved by using a temperature where catalase will be denatured or using dead carrot to show that the enzyme is actually present and working effectively. 3. Using the concentrations I have now, I could repeat the experiment until clear consistency is shown in the results. This would improve the accuracy and reliability of my results. 4. Collecting the gas in a different way. This could be done by measuring the time it takes for each concentration to release a certain volume of gas. This would also increase reliability. In general, my results are fairly inaccurate because of the slight change in temperature. The results are quite low in reliability because of the reasons previously mentioned. The validity of my conclusions is assisted by the support my results give to my initial hypothesis but because of the unreliability of my results and the limitations of the range and number of observations, no conclusions could be made concerning the optimum concentration of hydrogen peroxide for catalase. As a result of this, my conclusions can be seen as valid but not in their entirety. ...read more.

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