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Investigate how temperature affects the rate of reaction of the enzyme catalase on its substrate hydrogen peroxide.

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Introduction

Aim To investigate how temperature affects the rate of reaction of the enzyme catalase on its substrate hydrogen peroxide. Scientific Background Enzymes are biological catalysts which increase the rate of reactions by lowering the activation energy needed for the reaction to tale place. The activation energy is the amount of energy needed for molecules to react when they collide. Molecules need to collide in order to react, this is known as the collision theory. When they collide they may not react as a certain amount of energy is required to break bonds, this energy is the activation energy. Enzymes are made of a long amino acid chain, within this some molecules are attracted to each other, so the chain folds in on itself to form a 3D shape. How enzymes are shaped. An area on the surface of the enzyme is known as the active site. This is where reactions take place to form or break down substances. Enzymes are specific which means a particular enzyme only works on one substance known as its substrate. For example, the substrate of amylase is starch and the substrate of lipase is fats. They only have one substrate because the active site is formed in a different shape for each enzyme, where only one substance can fit. The 'lock and key' hypothesis states that the enzyme is like a lock which will only have one key. 'Lock and Key' hypothesis The substrate shown is the only substance that fits the enzyme. An enzyme substrate complex is the compound formed when the substrate is attached to the active site, it is only in this form for a short time while the substrate is being broken down. ...read more.

Middle

Using the same potato, as different potatoes will have different levels of catalase present, ? Using the same concentration of hydrogen peroxide, ? Using the same cork borer to cut the potato, to keep the surface area constant. The experiment will be safe by: ? Always wearing safety goggles, as hydrogen peroxide an damage your eyes, ? Not spilling the hydrogen peroxide as it is an irritant, and bleaches, ? Taking care when cutting the potato, ? Taking care when handling hot water. Results The results obtained are as follows: There was not enough time to conduct two repetitions, however, one repetition was conducted. The rest of the method was followed as planned. 1st Set of Results Gas collected (ml) with the following temperatures (?C) Time (s) 10 20 30 40 50 60 70 30 0.05 0.10 0.20 0.40 0.10 0.10 0.20 60 0.10 0.10 0.40 0.80 0.20 0.20 0.30 90 0.10 0.20 0.60 1.30 0.30 0.40 0.30 120 0.20 0.50 0.90 1.80 0.40 0.40 0.30 150 0.20 0.50 1.10 2.20 0.40 0.40 0.30 180 0.25 0.60 1.40 2.70 0.40 0.40 0.30 210 0.30 0.70 1.60 3.00 0.60 0.40 0.30 240 0.30 0.80 1.80 3.40 0.60 0.40 0.30 2nd Set of Results Gas collected with (ml) the following temperatures (?C) Time (s) 10 20 30 40 50 60 70 30 0.05 0.05 0.10 0.20 0.30 0.30 0.25 60 0.05 0.05 0.20 0.60 0.35 0.40 0.25 90 0.20 0.10 0.30 0.90 0.40 0.40 0.25 120 0.10 0.20 0.60 1.30 0.45 0.40 0.25 150 0.15 0.40 0.80 1.80 0.45 0.40 0.25 180 0.20 0.45 1.00 2.20 0.45 0.40 0.25 210 0.20 0.60 1.30 2.70 0.45 0.40 0.25 240 0.30 0.70 1.60 3.00 0.45 0.40 0.25 Averages Gas collected (ml) with the following temperatures (?C) Time (s) ...read more.

Conclusion

Hot and cold water were mixed to achieve accurate temperatures. An anomalous results occurred during the repeat reading of the 10?C experiment, the reading at 90 seconds is higher than that at 120 seconds. This reading was ignored when taking the average so It does not affect the analysis. It occurred because the measurement was misread, it may have been 0.1 cm3, instead of 0.2 cm3. Another anomalous result occurred during the first taking of the 50?C experiment, gas was released at 210 seconds when the experiment seemed to have stopped. The gas may have been trapped in the delivery tube and should have been released earlier in the experiment. This was taken into account when drawing the best fit line on the graph, so does not affect the analysis. The method used was good enough to achieve reliable readings , but it can be improved by measuring the mass of the gas lost, this would be more accurate as digital readings would be taken. Using a smaller frequency and a larger range of temperatures would give more evidence for the conclusion. However would require more time and equipment. Other improvements are, using thinner measuring cylinders, to measure out the hydrogen peroxide and the gas produced. Using a thermocouple thermometer to accurately measure the temperature. The hydrogen peroxide took time to heat up as the test tube is glass and is insulated. Using a better material would save time and would have allowed the plan to be completed. Using electronic equipment to take readings a exactly 30 seconds, would eliminate human error. Further work that would extend the investigation and give more evidence to the conclusion would be, to use different concentrations of hydrogen peroxide and lengths of potato, to see how these affect the rate of reaction. Using other substances with catalase, like liver, to see how enzyme concentration affects the rate. ...read more.

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