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Investigation on how the temperature affects the activity of the enzyme catalase in the decomposition of hydrogen peroxide.

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Introduction

Investigation on how the temperature affects the activity of the enzyme catalase in the decomposition of hydrogen peroxide PLANNING Aim - the aim is to find out the effect of temperature on the rate of reaction of an enzyme (catalase) by investigating the rate of decomposition of hydrogen peroxide. Three main factors will be measured: 1. Temperature - the optimum temperature of the enzyme (temperatures from 10�C to 60�C). 2. Oxygen - the amount released from the hydrogen peroxide, H2O2 (in cm3). 3. Time - the duration of the reaction (300 seconds). Scientific Knowledge Enzymes are complex three-dimensional globular proteins and acts as a biological catalyst, which alters the rate of a chemical reaction without itself undergoing a permanent change. They have a great significance involving the metabolic activities in living organisms. As the enzyme molecule is usually larger than the substrate molecule it acts upon, only a small part of the enzyme molecule comes into contact with the substrate. This region is called the active site. Catalase is an enzyme found in food such as potato and liver. It is used for decomposing hydrogen peroxide from cells, as it is a poisonous by-product of metabolism. Catalase speeds up the decomposition of hydrogen peroxide into water and oxygen, this is because the shape of the active site on the enzyme matches the shape of the hydrogen peroxide molecule so is able to bind with it. This type of reaction where a molecule is broken down into smaller pieces is an anabolic reaction. Hydrogen peroxide Water + Oxygen 2H2O2 (aq) ...read more.

Middle

Put the hydrogen peroxide in a beaker. Remove 10cm3 of the solution using a 10cm3 syringe. 6. Place the syringe into the hole in the bung and add the hydrogen peroxide to the potato discs in the conical flask. 7. Immediately start the stop clock. Record the volume of oxygen gas produced in the gas syringe every 30 seconds for a total of 300 seconds. 8. Repeat this method and increase temperature by 10�C each time until readings for 60�C is collected. Equilibration of the water in waterbath is very important because the temperature is known to fluctuate. For example there may be a temperature difference within the waterbath, therefore to ensure that the temperature of the water is the same in the waterbath, the water must be left for a period of time to come into balance. Using a couple of thermometers on either side can help in determining whether temperature is the equalised and stabilised. It is important to find out whether the hydrogen peroxide will react even when no enzyme is present and to see if any oxygen is given off - this will be the control. Diagram Variables 1. Independent Variable: - Temperature of solution, - Temperature of the water in the waterbath measured in �C using thermometers. 2. Dependant variable: - The volume of oxygen gas produced by the breakdown of hydrogen peroxide, which will be measured in cm3 in a gas syringe for 300 seconds. 3. Control Variables: - These variables, which can alter the rate of reaction, need to be kept constant all the time: Concentration of enzyme catalase: the higher the concentration, the higher the rate of decomposition of hydrogen peroxide. ...read more.

Conclusion

cannot be formed for a reaction to occur. When the enzyme (protein) is denatured it becomes less effective as a catalyst and soon the enzyme activity gets slower and then finally it stops. EVALUATION Limitation - It is quite different to make sure each and every potato disc is of the same size even though a ruler is used. Improvement - Vernier callipers, or a micrometer screw gauge can be used to measure the diameter of the potato discs- this would be more accurate than a ruler. Limitation - there were a few anomalies (see results table on page 7 highlighted in orange). Possible reasons might have been due to human error or contamination in the substrate. It could also be the temperature of the room. The experiment carried out on different days, some times the temperature in the room varied, from 23�C to 30�C. Improvement - Repeating the whole experiment - to eliminate anomalies and ensure the corrections of the optimum temperature. Limitation - Even though there were only a few anomalies, there was no way of determining the pH. Knowing the pH is essential as hydrogen ions are involved. Improvement ph meter could be used to determine the pH of the substrate hydrogen peroxide. A buffer solution could also be used, I can improve my method to give me better results by using a wider range of concentration of hydrogen peroxide. This would then give me more results in which I can use to draw up a better conclusion Temperature close to the optimum temperature, which is 40�C, could be investigated such as 39�C or 41�C to ensure the correct optimum temperature. A thermometer with a high resolution could be used for accuracy. Shimona Madalli The effect of temperature on catalase 4359 ...read more.

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