Enzyme Catalase

Enzyme Catalase
Background information: An enzyme is a large protein that acts as a biological catalyst and which changes the rate of a reaction. It provides an active site which is an environment where a reaction can take place this is made up of amino acids. The structure and shape of the substrate, the structure and shape of an enzyme and the substance upon which the enzyme works all have to match exactly. This enables the substrate to bind, but it can?t do this if the shapes of the two are different. An enzyme itself will not be affected by the reaction and if the reactants are released the enzyme can be bound with a new substrate. The enzyme I am investigating is catalase. Catalase is made in all organisms including yeast cells which will be used for my experiment. Catalase breaks down Hydrogen peroxide into water and oxygen. Hydrogen Peroxide Catalase = Water + Oxygen 2H2O2 H 2O O 2 There are many different factors which affect how catalase works. One of these is the temperature of the substrate. By increasing the temperature I will increase the rate of reaction. This is explained with the use of collision theory. When the temperature is increased the kinetic energy of the reactants are increased so more successful collision between the molecules of reactants so the rate of reaction is increased. Increasing the temperature therefore should increase the rate of reaction. All enzymes though have a specific ?optimum temperature? where the temperature is just right for the enzyme to work to its best potential.
This usually about 35â?? Celsius. However by increasing the temperature to much so that it is higher than the enzymes optimum temperature it will denature the enzyme and will be useful. This is because temperatures usually above 45â?? Celsius will damage the enzymes protein. Another factor which affects an enzyme is the PH of the substance. All enzymes have an optimum PH as well as an optimum temperature at which it will work best. Increasing the PH will increase the reaction rate until a certain point. However enzymes are denatured after a certain PH. There are other factors which will affect the rate of breakdown of Hydrogen peroxide. The concentration of the substrate will play a major part in the rate of reaction. Increasing the concentration of the substrate should increase the rate of reaction, since there are more molecules of Hydrogen peroxide to react resulting in more successful collisions, a higher amount of oxygen to be produced and increased rate of reaction. Also since yeast makes catalase the more yeast present in the reaction the more oxygen will be produced. Prediction: The higher the concentration of the Hydrogen peroxide the higher the rate of reaction. My prediction is that the rate of reaction is directly proportional to the concentration of the hydrogen peroxide or that the time taken by the reaction will be inversely proportional to the concentration. If the concentration is doubled the rate of reaction will be doubled. If the concentration is trebled then so will the rate of reaction. The basis of this prediction can be shown by looking at what the concentration does. A smaller concentration will mean that the molecules of Hydrogen peroxide will be less since there is more water. There will therefore not be many successful collisions between the enzyme and Hydrogen peroxide. By doubling the concentration there will be double the amount of hydrogen peroxide per cm3 less water and so double the amount of successful collisions, double the amount of oxygen and double the speed so half the time due to more successful collisions per second. By increasing the concentration each time by a factor I should be able o observe a constant. This is my preliminary results while using 10cm3 yeast trying each concentration twice as follows: Volume of Oxygen collected (cm3) Concentration of Hydrogen peroxide in total of 20cm3 (Hydrogen Peroxide: water) 5:15 (1/4) 10:10(1/2) 15:5(3/4) 20:0 (1) Time (minutes/seconds) 1st 2nd average 1st 2nd average 1st 2nd average 1st 2nd average 0.30 9 7 8 15 19 17 26 22 24 27 33 30 1 10 12 11 23 23 23 35 33 34 44 46 45 1.30 16 14 15 31 29 30 43 45 44 56 56 56 2 18 20 19 35 39 37 54 56 55 71 69 70 2.30 22 18 20 38 40 39 56 58 57 76 72 74 3 23 25 24 46 48 47 70 72 71 95 97 96 3.30 27 25 26 55 53 54 81 83 82 109 107 108 4 26 28 27 56 58 57 81 83 82 113 111 112 4.30 32 3 34 66 68 67 102 104 103 135 133 134 5 36 38 37 72 74 73 111 113 112 142 146 144 5.30 39 41 40 79 77 78 119 121 120 154 158 156 6 40 44 42 86 84 85 126 128 127 167 169 168 Time taken to collect 200cm3 Oxygen 31.25 31.03 31.14 25.24 15.50 15.37 10.20 10.30 10.25 8.00 7.36 7.48 The aim of the experiment is to investigate the factors which affect the action of the enzyme catalase during the breakdown of hydrogen peroxide into the components of water and oxygen. The apparatus available and which I will use are conical flasks, rubber bungs, measuring cylinders, rubber delivery tubes, plastic tubs, stop clocks, thermometers, yeast suspension, hydrogen peroxide. It will be set up as shown in the diagram. The independent variable which I have chosen to use is the concentration of hydrogen peroxide based on my preliminary work. It is much more difficult to do temperature for example since it is difficult to regulate. Also the concentration is the only variable which is likely to give me a mathematical correlation. The dependent variables I have decided to choose are the amount of oxygen produced every 30secs and the time taken for 200cm3 Oxygen to be collected. I will carry out this experiment using different concentration of hydrogen peroxide with water, so that the total volume will be 30cm3. I will use 30cm3 of undiluted Hydrogen peroxide, 25cm3 2H2O2 with 5cm3 water 20:10, 15:15, 10:20, and finally 5cm3 Hydrogen Peroxide with 25cm3 water. There are plenty of values therefore to make a mathematical analysis. I found that 20cm3 of solution was not enough in my preliminary work. Method: I will fill the plastic tub halfway with water and the 200cm3 measuring cylinder to the brim with water. I shall place the measuring cylinder in the tub with the opening at the bottom making sure no water is lost from the measuring cylinder. I will place one end of the delivery tube in the cylinder and attach the other to the bung. I will then put 10ml of yeast suspension in the conical flask. I shall then have to pour the hydrogen peroxide and water in the flask close the bung and get someone else to start the stop clock. Time permitting I will do this 3 times for each concentration and take an average. This should give me accurate results for which to make my mathematical analysis. I will change only the concentration of hydrogen peroxide and leave all other variables the same therefore making a fair test. I will make sure I do not come in contact with Hydrogen peroxide since when it reacts with water it forms caustic soda. Other then this the experiment is quite safe.

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