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Design an experiment to investigate the substrate concentration on the rate of activity of the enzyme catalase.

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Introduction

Biology Substrate Experiment Gopal Makwana 12AT 04/05/07 Design an experiment to investigate the substrate concentration on the rate of activity of the enzyme catalase. Enzymes such as catalase are protein molecules, which are found in living cells. They are used to speed up specific reaction within the cell. They are all very specific as each enzyme just performs one particular reaction. Catalase is an enzyme found in food such as potato and liver. It is used for removing Hydrogen Peroxide from cells. Hydrogen Peroxide is the poisonous by-product of metabolism. Catalase speeds up the decomposition of Hydrogen Peroxide into water and oxygen. The substrate that I shall be using is H2O2, which is Hydrogen Peroxide, and the enzyme catalase that I shell use is lamb liver. The enzyme catalase carries out the following reaction: H2O2 + H2O2 = 2 H2O + O2 It takes two molecules of hydrogen peroxide and converts them to two water molecules plus a molecule of oxygen gas. A common test for the presence of catalase in bacteria involves suspending a sample of the microbes in a dilute solution of hydrogen peroxide. If the organisms produce catalase, bubbles form in the solution from the release of oxygen. As with all enzymes, catalase is a protein, meaning that it is synthesised within the cell from building blocks called amino acids. In addition to the amino acids that make up the protein, catalase carries around a heme group. In the middle of the heme group sits an iron atom (see the picture below). The catalase enzyme uses this iron atom to help it break the bonds in the two molecules of hydrogen peroxide, shifting the atoms around to release two molecules of water and a molecule of oxygen gas Biology Substrate Experiment Gopal Makwana 12AT 04/05/07 This is an experiment to examine how the concentration of the substrate Hydrogen Peroxide (H2O2) ...read more.

Middle

This is due to the maximum number of reactions being done at once, so any extra substrate molecules have to wait until some of the active sites become available. In the experiment I had to make a few changes. These were to make the experiment better on the teacher's advice or the correct apparatus was not available in the school laboratory. * I cut the liver into pieces and weighed them so each piece was one gram in mass. After cutting the liver I used the pastel and mortar to grind the liver to give it a greater surface area so the reaction would be helped. When the liver was getting grinned I added a pinch of sand to stop the liver from becoming totally liquid. Biology Substrate Experiment Gopal Makwana 12AT 04/05/07 * I had to use a measuring cylinder to measure the amount of gas given off because there weren't enough gas syringes in the school laboratory. The gas syringes also break very easily if too much gas goes into them so we had to use the measuring cylinders. * Gloves were worn throughout all the experiment because the hydrogen peroxide is corrosive and thus safety precautions were taken in event of any accidents. * The solutions that I used for the experiments were hydrogen peroxide and distilled water. The different concentrations of the solutions that I used were Distilled Water Hydrogen Peroxide Substrate Concentration 20 cm3 0 cm3 0% 16 cm3 4 cm3 20% 12 cm3 8 cm3 40% 8 cm3 12 cm3 60% 4 cm3 16 cm3 80% 0 cm3 20 cm3 100% In order to decide how varying the substrate concentration affected the decomposition of the enzyme (liver), the rate of reaction was measured. When the solutions and the liver were placed in the conical flask the stopwatch was started once the rubber bong was sealed. In the conical flask it was clear that a reaction was taking place by the observation of bubbles of oxygen gas being released creating a 'fizzing' in the conical flask. ...read more.

Conclusion

I would change the time scale about three minutes to give the gas time to get measured. * Human Reactions - The reaction starts as soon as the liver meets the hydrogen peroxide. The bong must be placed on the conical flask as soon as possible to collect all the gas released. In most of my experiments the bong was not placed on immediately so gas was lost. Basically I would have to get familiar with the apparatus so I can do it quickly. * Repetition - Also as I repeated the experiments so many times the later experiments will be more accurate as everything becomes more familiar then the first attempts. In this experiment six different substrate concentrations were Biology Substrate Experiment Gopal Makwana 12AT 04/05/07 tested. However, although there were a large ranges in between the concentrations. The rate of reaction can be predicated from the graph at the points that were not tested. In a future investigation, a far greater number of substrate concentrations between those already recorded should be tested reducing the extent of any anomalies on a graph where the line of best fit must be drawn. I would recommend using 5% differences instead of 20% ones that I used. The experiment can also be repeated a further times, the greater number of times a experiment is carried out the better as this gives a much better average and would nearly completely remove all anomalous results. From looking at the results and summarising the limitations of the experiment I feel as if I can come to a conclusion to the aim of the experiment. The aim was 'Design an experiment to investigate the substrate concentration on the rate of activity of the enzyme catalase.' Basically the firm conclusion is that as the substrate concentration is increased the rate of activity for the enzyme is also increased. I cannot say that if it is directly proportional from the results I have got, as the experiment would have to be redone with the suggestions that I have put forward as the limitations in the experiment. ...read more.

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