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The effect of substrate concentration on the activity of catalyse.

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AIM: The effect of substrate concentration on the activity of catalyse PREDICTION: I predict that, as substrate concentration increases, initially the rate of reaction will also increase. However after a certain point the catalyse stops having the ability of working any faster. Thereafter after this point the rate of reaction cannot increase any further. Enzymes are protein molecules, which can be defined as biological catalysts. A catalyst is a molecule, which speeds up a chemical reaction, but remains unchanged at the end of the reaction. (Jones, 2000: 43) There are two types of possible catalyst reactions that can occur: * A reaction in which a larger molecule is broken down into a smaller molecule. Fig 1.1: In this experiment I will be monitoring this reaction, which shows the break up a large molecule, hydrogen peroxide, to form smaller molecules, water and oxygen. The graph below shows that as substrate concentration increases the rate of reaction also increase up till a certain point known as V-max. This is how I expect my graph to look like after the experiment. Fig 1.2: (Williams, 2000: 70) The human body produces this catalyse in cells to prevent the accumulation of hydrogen peroxide, a substance that is toxic and a waste product in cells. * A reaction in which smaller molecules combine to form a larger molecule. Fig 1.3: The formation of a dipeptide molecule from two amino acids. (Williams, 2000: 63) This reaction involves the break down of hydrogen peroxide, H O , into water and oxygen. Potatoes will be used as a source of catalyse. These biological catalysts are known as globular proteins (amino acids). The name comes hence from its spherical and globular structure. These globular structures can also be defined as having a tertiary structure. This is as a result of the three types of bonds holding the catalyst together. Hydrogen bonds: These form between the R groups and are relatively weak. ...read more.


* Now that my equipment is ready I will add the hydrogen peroxide to the potato solution, quickly place the rubber bung so that no oxygen is lost and begin the stopwatch so that I can note the increase in the production of oxygen over the three minutes. * I will record my results in a results table. * I will repeat this procedure for this concentration but also for the other concentration 1.0, 1.5, 2.0, 2.5, 3.0, to get rid of anomalous results. * During this experiment I will have to make sure that I wash all my equipment efficiently to ensure that the different concentration do not get mixed up. SAFETY: * It is important to clear away all bags and un-necessary equipment from the workbench. All stools should be placed under the table to prevent accidents. I will make sure that I am working in a well spaced out area to decrease the amount of spillages. * When handling hydrogen peroxide it is important to wear gloves as it is extremely irritant and at strong concentration can be corrosive. It is an oxidant therefore it needs to be kept away from heat and stored in a fireproof cabinet. * It is also important to place clamps around places of equipment that is unstable. * To protect clothing a lab coat should be worn. RESULTS: Experiment 1 Time (secs) Concentration (mol) 0.00 0.15 0.30 0.45 1.00 1.15 1.30 1.45 2.00 2.15 2.30 2.45 3.00 0.5 0.0 1.0 2.1 3.6 4.2 5.0 5.8 6.4 7.0 7.5 7.9 8.3 8.4 1.0 0.0 1.4 2.9 4.2 5.3 6.4 7.5 9.0 9.0 10.6 11.5 12.3 13.0 1.5 0.0 2.0 3.6 5.3 6.8 6.8 9.4 10.8 11.9 13.2 13.2 14.0 14.8 2.0 0.0 2.6 4.6 6.4 7.9 9.4 10.8 12.1 13.4 14.6 15.8 16.0 16.1 2.5 0.0 4.0 6.0 8.0 9.6 11.3 12.0 12.8 14.0 14.6 15.4 16.0 16.6 3.0 0.0 5.1 7.3 9.4 11.2 13.1 15.1 17.0 18.6 19.8 20.7 21.5 22.0 Experiment 2 Time (secs) ...read more.


As this occurred water may have gone into the delivery tube causing blockages. * The temperature of the classroom would have increased due to the number of people in the classroom. This may have effected my results as the catalyse or the substrate may have easily evaporated. Justifications (Improvements) * My results would have been more accurate if I had someone to help with the time. * I would use pH 7 buffer solution. * I would use a gas syringe. * Once I added in the hydrogen peroxide to the catalyse I would use my thumb to cover the test tube rather than a rubber bung with plaster sine. * The experiment could have been conducted in an area where the temperature was controlled. * I would liquidise the potato myself. * I would use a rubber delivery tube rather than a glass tube. * This would ensure that I was not doing two things at once and so therefore I would be able to produced more reliable results. * This would provide the catalyse with neutral conditions and so therefore this variable would be kept constant. Increasing the accuracy of the experiment. * The gas syringe has more clear and visible markings so I would have been able to see the volume of oxygen produced more clearly. The differences in the equipment means that the meniscus would be straight rather than curved which means that human error in taking these readings would be less likely to occur. * This would make sure that oxygen was not lost due to the rubber bung having holes. My thumb placed tightly over the test tube would prevent oxygen from escaping. * This would make sure that this variable was kept constant and the environmental changes would not affect my results. * I would be able to make sure that different strength catalyse from different potatoes was not mixed together. In turn my results would be more accurate as the liquidised potato would be pure. * A rubber delivery tube is less likely to acquire blockages compared to the glass delivery tube. ...read more.

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