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The Effect of Temperature on Enzyme Activity.

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The Effect of Temperature on Enzyme Activity The Intro Hydrogen peroxide (H2O2) is made as a by-product of many biochemical reactions in most organisms. It is harmful as it is an oxidising agent (it has too much oxygen per molecule, which readily reacts with many of the compounds in organisms). Since most organisms produce this harmful substance, they must all have a mechanism of getting rid of it. Organisms can get rid of hydrogen peroxide by converting it to water (H2O) and oxygen (O2), which are both useful substances. 2H2O2 ( 2H2O + O2 (balanced equation) The mechanism (of converting hydrogen peroxide into water and oxygen) is carried out (or catalysed) by an enzyme called catalase. As hydrogen peroxide is found in most organisms, catalase is also found in most organisms. Catalase is found in humans, ants and even potatoes! (Which means we have to use them, every time.) Potatoes = Cheap things that can be used in any biological experiment (Well, virtually any experiment) Potatoes are cold blooded i.e. they cannot regulate and maintain a constant internal temperature. Therefore potato catalase is exposed to a wide range of temperatures in which it has to function. The Aim (and co.) The aim of the experiments is to investigate the effect of temperature upon the rate of activity of the enzyme catalase (potato catalase). Catalase catalyses (i.e. acts as a catalyst, as the name suggests, or speeds up) the break down of H2O2 into H2O and O2. The oxygen is produced in gaseous form. By collecting and measuring the amount of oxygen gas produced we can measure the rate at which oxygen gas is produced and therefore, we can measure the rate of catalase activity. ...read more.


Using a thermometer, check that the temperature of the water bath and the temperature of the hydrogen peroxide is the desired temperature (by simply putting one thermometer in the water bath and another is the boiling tube). The experiments should begin with 10 �C. 5. After the desired temperature is obtained, and only after, bore out a 6 cm long core, 1 cm in diameter (the overall shape being a cylinder). Further cut the core into 12 smaller pieces (creating small discs), each with a length of 0.5 cm. Such discs fit easily into the boiling tube and provide an ample surface area. The core should only be cut after the desired temperature is reached because if the potato cores are cut beforehand, and are therefore left in the open air, they dry up and this could damage the enzyme or restrict its activity. Therefore it is advisable to only cut the cores out when the hydrogen peroxide is ready. 6. Place the 12 discs into the boiling tube and immediately place the bung over the boiling tube. This prevents any of the oxygen gas escaping. Once the bung is placed on top of the boiling tube, begin timing the experiment (i.e. start the stopwatch). Mark where the dyed water, in the U-shaped manometer, began. The apparatus is designed so that as oxygen is produced from the breakdown of H2O2, it remains in an enclosed system. As more oxygen gas is made, the pressure in the system increases. This increase in pressure will push the dyed water out of the U-shaped manometer, so the water line will go down on the left hand side of the manometer and rise in the right hand side. ...read more.


In plan, I had a temperature range between 10 �C and 60 �C with 10 �C intervals. In the actual practical the range was reduced (from 20 �C to 60 �C, the intervals were kept the same). This gives fewer results to investigate and so there is less evidence to build a firm conclusion on. From the results, the optimum temperature is around 30 �C. However the 10 �C intervals make it difficult to find the exact optimum temperature. Having intervals of 5 �C would There was another problem with the timing of the experiment. Originally, I planned to keep the potato cores in the hydrogen peroxide solution for 15 minutes and in the procedure we had to keep the experiment running for only 5 minutes. In the higher temperatures, not much oxygen was made. In fact, so little oxygen was made that it was difficult to measure the volume produced as the scale on measuring cylinder began at 1 cm3. If the experiments were to last 15 minutes, more oxygen could have been made and it would have been easier to measure the volume of oxygen produced. Although there is a general pattern in the results, they do vary. This does not mean that they are anomalous. These variations could be caused by many factors. For example, not all of the students used the same potato. This would mean that there are two possible differences, being the type of catalase and its concentration per disc. To eliminate these variations, it would have been better for the group of students to use the same potato, as it is more likely that the concentration and type of catalase will be similar if not the same. This would make the procedure a fairer test. ...read more.

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