Temperature's Effect on the Production of Oxygen From Yeast and Hydrogen Peroxide

Temperature's Effect on the Production of Oxygen From Yeast and Hydrogen Peroxide
My aim is to discover how temperature effects the production of oxygen from yeast and hydrogen peroxide. I will mix yeast with hydrogen peroxide and use an upturned measuring cylinder to measure how much oxygen is produced. To find out how much hydrogen peroxide and yeast I will use, I will carry out pre-tests. This will also aid accuracy of the final experiment by uncovering potential flaws in the method. Hypothesis and Theory -????????? There are many ideas to suggest that the change in temperature will cause an increase of respiration in yeast. Yeast is a single cell fungus made up mostly of protein, which has been use for its applications in fermentation. Yeast, after activation creates the ferments carbon dioxide and ethyl alcohol by secreting the enzyme zymase (a complex of 12 enzymes) in the yeast, which acts on simple sugars such as glucose. The alcohol produced has been used in making wines and bears and the carbon dioxide produced has been used in baking as it gets trapped in the dough and causes it to rise. Enzymes are catalysts which speed up reactions, they are made from protein and are specific as to which substrate they work on.
Enzymes basically work due to the lock and key theory, where the substrate substance (the key) fits into the active site on the enzyme and they bind together, the reaction takes place and the substrate unlocks to form one or more substances leaving the enzyme ready to perform the binding again. An enzyme can only bind with a substrate that fits the shape of the active site unique to that kind of enzyme. The induced fit theory states that the substrate cannot bring about catalysis and the reaction itself, but the active site, when it comes into contact with the substrate slightly changes its shape to form an effective fit and arrangement of catalytic groups on its surface, which brings about the catalysis reaction. To display this, think of a hand in a glove where the hand acts as the key and substrate, inducing a change in the shape of the glove, which acts as the enzyme. When some substrate substances induce a fit with the enzyme, the enzyme may not be able to accept some other substrates. Yeast has to make energy, stored as AP to carry out cellular functions. To do this they can respire both aerobically when there is plenty of oxygen, but where oxygen is short, they respire anaerobically; which makes them partial anaerobes. This produces less energy, but keeps the yeast alive. Pyruvic acid has to be broken down in respiration when formed by the breaking down of glucose molecules. Kinetic theory states that, with an increase in temperature, the rate of reactions will increase. This is due to the increase of speed of the particles, brought about by the extra energy given to them by heat. Faster particles will bring about more particle collisions and so the reaction will take place faster. Enzymes are sensitive to temperature changes up until a certain temperature and will increase in their reactivity also. The reactions that take place in the enzymes will be quicker and so will create more of their products. Enzymes are sensitive to temperature up until a certain temperature where the shape of the active site is altered drastically, so much so that binding hardly ever takes place. This is called denaturisation. Catalase is a common enzyme found inside many cells and tissues. It destroys hydrogen peroxide, which is a poison if it is allowed to build up inside the cells. The reaction is: Hydrogen peroxide ?→ Water + Oxygen The enzyme is often used, as it is quite easy to see the froth caused by the oxygen being given off. This means that you can monitor the rate of the reaction quite easily. More accurate experiments will actually collect the oxygen and measure its volume. With reference to my theory, I predict that the rate and speed of respiration of glucose by yeast will increase with temperature rise, up until a certain point where the enzyme used and secreted by the yeast will become denatured and cease to function, reducing the rate significantly. This is explained through kinetic theory, yeast respiration, the nature of enzymes and Catalase. I will carry out two pre-tests. The equipment I will use: 1 Water Bath 1 Test Tube 1 Upturned Measuring Cylinder 2 Clamps 1 Piece of Rubber Tubing connected to a Bung 0.1g of yeast 3ml Hydrogen Peroxide A Balance (to weight the yeast) A Pipette Stop Clock It will be set-up as follows: Possible variables I could use: Temperature Amount of H2O2 Amount of Yeast How the variable will affect the final result: temperature -???? Temperature of the experiment will have a great effect on the results as explained by kinetic theory. Temperature will affect the rate of the yeast?s respiration. I shall keep the temperature of the mixture and water bath under control by using a thermometer and checking it constantly. I shall keep swirling the thermometer to keep the heat distributed. amount OF H2O2 The amount of hydrogen peroxide will affect the results also, as more H2O2 means that there are potentially more products, which would make the results accurate or the experiment fair. The H2O2 will be measured out in a small measuring cylinder each time. amount OF yeast The amount of yeast is crucial, more yeast means more H2O2 will be respired and more products created. An imbalance will upset the results. The amount of yeast will be weighed out on an accurate balance each time. In my experiment, my controlled variables will be the amount of yeast and H2O2. The independent variable will be the temperature and the dependent variable will be the amount of oxygen produced. pre-test results Temperature: 20?C Time (minutes) Oxygen Produced (cm3) 1 2.5 2 5 3 9 4 13 Temperature: 55?C Time (minutes) Oxygen Produced (cm3) 1 17 2 19 3 20 4 20 Method In my final experiment I will use the same method as I used for the pre-tests. I will set up the equipment as I did before and use the same equipment. When the hydrogen peroxide is in the test tube, I will start the timer, the bung will go on and the H2O2 will react with the yeast and produce oxygen which will travel up through the bung, through the tube and go into the upturned cylinder and displace the water, which goes out through the bottom. After the experiment is complete, a new test tube will be used. The experiment will be carried out ten times: twice at each of the following temperatures: 20?C, 30?C, 40?C, 50?C and 60?C. Obtaining results Temperature: 20?C Test 1 Time (minutes) Oxygen Produced (cm3) 1 2 2 6 3 11 4 13 Test 2 Time (minutes) Oxygen Produced (cm3) 1 2.5 2 6 3 10 4 12 Temperature: 29?C Test 1 Time (minutes) Oxygen Produced (cm3) 1 4 2 12 3 13 4 13 Test 2 Time (minutes) Oxygen Produced (cm3) 1 6 2 8 3 12 4 13 Temperature: 39?C Test 1 Time (minutes) Oxygen Produced (cm3) 1 9 2 11 3 12 4 15 Test 2 Time (minutes) Oxygen Produced (cm3) 1 8 2 12 3 14 4 15 Temperature: 48?C Test 1 Time (minutes) Oxygen Produced (cm3) 1 7 2 11 3 13 4 13 Test 2 Time (minutes) Oxygen Produced (cm3) 1 7 2 11 3 13 4 14 Temperature: 59?C Test 1 Time (minutes) Oxygen Produced (cm3) 1 16 2 19 3 21 4 21 Test 2 Time (minutes) Oxygen Produced (cm3) 1 17 2 20 3 21 4 22 I have ensured that my results are as accurate as possible by controlling all the variables stated in my planning section. I also took care when using the equipment so as to retain continuity throughout the experiment. For this, I checked everything was set up correctly at each reading and prepared my solution in the same way. I did not prepare a batch of solutions as this would have given some more time to acclimatise and more time to react and respire, changing the conditions. averages Temperature: 29?C Time (minutes) Oxygen Produced (cm3) 1 2.25 2 6 3 10.5 4 12.5 Temperature: 39?C Time (minutes) Oxygen Produced (cm3) 1 5 2 10 3 12.5 4 13 Temperature: 48?C Time (minutes) Oxygen Produced (cm3) 1 7 2 11 3 13 4 13.5 Temperature: 59?C Time (minutes) Oxygen Produced (cm3) 1 16.5 2 19.5 3 21 4 21.5 To carry out a safe experiment, I wore goggles. I made sure not to spill any H2O2 and carried the jugs of hot water in two hands to avoid dropping it. Analysis My results show that if you increase the temperature, the rate of reaction increases. but, as you get to a higher temperature, the reaction takes place in the first minute and doesn?t react much in the next three, as seen in the experiment using water of the temperature 59?C. This is the denaturisation of the yeast?s enzymes. The results prove my theory and hypothesis as follows: Enzymes are catalysts which speed up reactions, they are made from protein and are specific as to which substrate they work on. Enzymes basically work due to the lock and key theory, where the substrate substance (the key) fits into the active site on the enzyme and they bind together, the reaction takes place and the substrate unlocks to form one or more substances leaving the enzyme ready to perform the binding again. An enzyme can only bind with a substrate that fits the shape of the active site unique to that kind of enzyme. The induced fit theory states that the substrate cannot bring about catalysis and the reaction itself, but the active site, when it comes into contact with the substrate slightly changes its shape to form an effective fit and arrangement of catalytic groups on its surface, which brings about the catalysis reaction. To display this, think of a hand in a glove where the hand acts as the key and substrate, inducing a change in the shape of the glove, which acts as the enzyme. When some substrate substances induce a fit with the enzyme, the enzyme may not be able to accept some other substrates. Yeast has to make energy, stored as atp to carry out cellular functions. To do this they can respire both aerobically when there is plenty of oxygen, but where oxygen is short, they respire anaerobically; which makes them partial anaerobes. This produces less energy, but keeps the yeast alive. Pyruvic acid has to be broken down in respiration when formed by the breaking down of glucose molecules. Kinetic theory states that, with an increase in temperature, the rate of reactions will increase. This is due to the increase of speed of the particles, brought about by the extra energy given to them by heat. Faster particles will bring about more particle collisions and so the reaction will take place faster. Enzymes are sensitive to temperature changes up until a certain temperature and will increase in their reactivity also. The reactions that take place in the enzymes will be quicker and so will create more of their products. Enzymes are sensitive to temperature up until a certain temperature where the shape of the active site is altered drastically, so much so that binding hardly ever takes place. This is called denaturisation. Catalase is a common enzyme found inside many cells and tissues. It destroys hydrogen peroxide, which is a poison if it is allowed to build up inside the cells. The reaction is: Hydrogen peroxide ?→ Water + Oxygen The enzyme is often used, as it is quite easy to see the froth caused by the oxygen being given off. This means that you can monitor the rate of the reaction quite easily. More accurate experiments will actually collect the oxygen and measure its volume. The graph shows a trend: if the temperature is increased, the reaction is faster- up to a certain point. Evaluation I have found that as I increased the temperature of the yeast solution, the rate of respiration of the yeast increased to a certain point where, as the temperature rose to a certain level, (in my case about 59?C) the rate of respiration eventually cut off. My hypothesis and prediction can e backed up with the findings; from looking at my results and graphs you can see the rise and fall of respiration. Thus my hypothesis and prediction are shown to be present and displayed to a large extent. They are explained due to the theories of enzyme-substrate with lock and key and kinetics. Where these meet is when kinetic theory states that an increase in temperature means more particle collisions between reactants and so a faster rate of reaction; and in enzyme-substrate where the enzyme is sensitive to heat, and about a certain temperature, the active site will begin denaturing, so slowing and eventually stopping the reaction. This will give an area where the rate of respiration drops off and goes to nothing instead of a precise cut-off point. These both apply to my experiment and were described in my planning section. My results were fairly close, which means they are fairly reliable. If there are any inaccuracies, they can be explained. The yeast was in little balls, if it was completely crushed to a powder the surface area would be increased therefore putting the bung on. If the yeast wasn?t left in the test tube in the heated water, the yeast might not acclimatise to the selected temperature before the hydrogen peroxide was added. This would mean the temperature is not affecting the temperature. All three of these could make the experiment inaccurate. To make sure that the results were as reliable as I could make them, I calculated the mean of two results at each interval when dealing with the rate. The obvious anomalous result is at 3 minutes with temperature 39C, this could be due to the afore mentioned flaws in the method. I took all possible precautions to make the apparatus used to be reliable and give good values do I think the slight unreliability was caused by the preparation of the solution and the unpredictability of how the reaction went that came with it. To obtain more reliable results I would want complete continuity with preparations, maybe arranging sets of substances to create multiple solutions beforehand or preparing them but not actually activating the yeast so as to prevent any getting a head start over the others. This would ensure that all the preparations are the same and would give continuity. This would help give more reliable results throughout. If I were to further investigate this experiment and my results, I would probably want to calculate the point where the enzymes begin to denature for respiration in yeast. I could also examine the change in rate between the intervals to determine validity and continuity, also running them through maybe more intricate calculations involving log. At this stage, I shouldn?t think there is too much more I can do. I think it would be interesting to vary the amount of H2O2 as an extension.

Temperature's Effect on the Production of Oxygen From Yeast and Hydrogen Peroxide 8.6 of 10 on the basis of 1953 Review.