The Effect of Hydrogen Peroxide on Potatoes

The Effect of Hydrogen Peroxide on Potatoes
Experiment to find out the effect of hydrogen peroxide on potatoes and to see if the surface area affects the amount of froth produced Introduction: (Sources: Internet, Biology Book, Chapter on Enzymes) Enzymes such as catalase are protein molecules, which are found in living cells. They are used to speed up specific reactions in the cells. They are all very specific as each enzyme just performs one particular reaction. They are known as biological catalysts (substances which speed up reactions but which do not get used up themselves) Enzymes help to turn the substrate into the product. The enzyme has an active site that helps it to recognise its substrate in a very specificway. Just like a key only fits into a specific lock, each enzyme has its own specific substrate. This is called the lock and key theory. Of course all enzymes have a specific temperature that they work that perfectly at, that makes them collide more frequently. If they get hotter than this temperature, which is usually about 45Â?C (some have certain microbes which can work at higher temperatures) the enzyme dentures and stops working. Catalase is an enzyme found in food such as potato and liver
It is used for removing Hydrogen Peroxide from the cells. Catalase speeds up the decomposition of Hydrogen Peroxide into water and oxygen. It is able to speed up the decomposition of Hydrogen Peroxide because of the shape of the Hydrogen Peroxide molecule. This type of reaction where a molecule is broken down into smaller pieces is called an anabolic reaction. A word equation for this is: Catalase Hydrogen Peroxide èèèèèèèèWater and Oxygen A diagram for enzyme activity: Key Factors: (Source: Biology Book) In my experiment the key factors that could affect the results of my experiment will be: 1. The temperature of the surroundings and test tubes 2. The pH value of its surroundings 3. The substrate volume 4. Mass of enzyme used 5. Surface area of active site ? the one variable I am going to change for my experiment Of course, the rest of these factors will have to be kept the same to keep the experiment a fair test. To do this, the experiment will take place in the lab where the conditions are frequently the same and the equipment should be kept the same to ensure all results are taken without any advantages or disadvantages over any of the other experiments. Everything in the experiment should be kept the same apart from the surface area of the potato which will be cut by the same scalpel and I will also try to cut it so they are basically the same size. Safety: To make sure that I am safe while carrying out the experiment, I must: 1. Wear safety goggles even before I start, as Hydrogen Peroxide is an irritant that if gets in your eyes could be very harmful. Also if it falls onto your skin it could cause a rash and persistent itching. 2. Putting all stools underneath the desk is vital as it could be dangerous of it is lying around and somebody knocks into it. 3. Never sit down on the experiment, and don?t take your eye off what is happening. Prediction: I think that the enzyme will react greater with the potato and produce more froth when it is cut up. This is because as you cut it up into smaller bits, you make the surface area greater meaning there are more enzymes to react with each other, and there will be more successful collisions between the two reactants. Preliminary work Before we did the final experiment we did a run through to check that we knew what we were doing. This gave us a rough estimate of what the results would be, and see if our predictions were right. It also told us how to conduct he experiment properly, and we worked out how we were going to measure the froth, which was to measure just the froth, and not the remaining liquid. Our results for the preliminary work were: Number of cuts made Amount of froth produced (mm) 1st result 2nd result No cuts 16 15 1 cut 25 23 Apparatus List: Equipment Use 1 scalpel To cut the potato into exact pieces (½, ¼ etc.) Potato (10×1cm³) Contains the enzymes to react with the hydrogen Peroxide Hydrogen Peroxide (55ml³) Reactant 1 pair of Safety glasses To protect your eyes from irritant chemicals 2 test tubes To put the two reactants in 1 test tube rack This is to store the test tubes in 1 Pipette Dispense Hydrogen Peroxide into measuring cylinder 1 ruler To measure the froth height 2 measuring cylinders Measure accurately 5ml³ of hydrogen peroxide to pour into test tube 1 Stop watch To time experiment (5 minutes) 1 Tile To store the potato on and to cut it up on 1 pair of tweezers Move the potato around without losing any of the enzymes My Experiment Method: The first thing I will do will be to put on my safety glasses and push stools under as this test needs to be made safe before anything can be done. I will then get the equipment I need for the experiment, which is listed above. Once everything is set up, (i.e. test tubes in test tubes in racks) I will, using a pipette, get 5ml³ of hydrogen peroxide and measure it out accurately into a measuring cylinder. This will have to be done at eye level so it is measured correctly. Do this into two separate measuring cylinders. Now I will pick up a whole piece of a 1cm³ potato with the tweezers and deposit it into the test tube. Once I have done this into two test tubes, I will pour the hydrogen peroxide measured out earlier into the test tubes and start the timer. This will now be watched carefully for five minutes, without sitting down. While this first experiment is underway I will get the potato cube and cut it into halves, and again measure 5ml³ of hydrogen peroxide into the measuring cylinders. Once the first experiment has finished, I will take the measurement of the froth, from bottom to top. I will only measure the froth though, and not the surrounding liquid. I will then take this result down. I will then repeat this method for ½, ¼, â??, and 1/16 of a 1cm³ piece of potato. I will do this twice so my results are reliable, and then I can tell if there are any anomalous results. I will then take an average of these results. Results: Results in millimetres Test Tube A Test Tube B Average Whole 1cm³ cube 31 26 28.5 1/2 of a cube 40 36 38 1/4 of a cube 53 52 52.5 1/8 of a cube 54 56 55 1/16 of a cube 75 70 72.5 Conclusion: (Sources: Science Book, Internet) I think that the enzyme will react greater with the potato and produce more froth when it is cut up. This is because as you cut it up into smaller bits, you make the surface area greater meaning there are more enzymes to react with each other, and there will be more successful collisions between the two reactants. This is my original prediction and I think it matches the results quite well. As I made the surface area bigger, the reaction that took place was quicker and produced more froth. As I predicted, the more surface area that was on the active site, the more froth would be produced (oxygen), which is a product of this equation. This is shown in my results as there is a definitely a pattern throughout the experiment that backs up my prediction. This is because the molecules are always moving around normally anyway and are fitting into the active site all the time. Of course this reaction can be sped up by changing something. In our experiment we changed the surface area, meaning that the substrate had more places to work in because the potato was opened. Thus because of this, it could produce the oxygen quicker and more often. Evaluation: I thought that I followed my method well enough to produce some good results. Even though, I think that I could easily improve my method. Firstly, to improve the fair testing I could have done all the experiments all at the same time as then they would have been subject to the same conditions, and might not have some enzyme traces left in the test tube when it is emptied out to use again. Also cutting up the potato was a problem as it was not guaranteed to be the same shape all the way through and cutting it into 1/16ths became very difficult to get exactly right. Another problem that I encountered was when I was taking the results, with the ruler. I don?t think was the most accurate way of taking the results as there is a lot of room for human error with the shaking of the hand. Also it was on the outside of the test tube which isn?t very accurate as it could be a different shape going up the test tube. I repeated my results once for each type of cut, which vastly improved the results because if their was an anomalous one, then it could be corrected into an average even though this could create a problem as it would drag the average down or up depending on the result. I?d say most of our results were fine except for two obsolete figures that where at the 1/8 cut. The results seem to slow down some what here, and the last result to seem to have sloped off. I think that it should be a straight line for my results and my average graph clearly shows Overall, due to reliable repeats and in general predictions being confirmed I feel my results are reliable enough to make a conclusion.

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