Investigating the Effect of Catalase Enzymes on the Decomposition of Hydrogen Peroxide

Investigating the Effect of Catalase Enzymes on the Decomposition of Hydrogen Peroxide
Background Information: Enzymes are large proteins that speed up chemical reactions. In their globular structure, one or more polypeptide chains twist and fold, bringing together a small number of amino acids to form the active site, or the location on the enzyme where the substrate binds and the reaction takes place. Enzyme and substrate fail to bind if their shapes do not match exactly. This ensures that the enzyme does not participate in the wrong reaction. The enzyme itself is unaffected by the reaction. When the products have been released, the enzyme is ready to bind with a new substrate. [image] Enzymes are classified into several broad categories, such as hydrolytic, oxidizing, and reducing, depending on the type of reaction they control. Hydrolytic enzymes accelerate reactions in which a substance is broken down into simpler compounds through reaction with water molecules. Oxidizing enzymes, known as oxidases, accelerate oxidation reactions; reducing enzymes speed up reduction reactions, in which oxygen is removed
Many other enzymes catalyze other types of reactions. Individual enzymes are named by adding ase to the name of the substrate with which they react. The enzyme that controls urea decomposition is called urease; those that control protein hydrolyses are known as proteinases. Some enzymes, such as the proteinases trypsin and pepsin, retain the names used before this nomenclature was adopted. Enzymes are typical catalysts: they are capable of increasing the rate of reaction without being consumed in the process. Some enzymes, such as pepsin and trypsin, which bring about the digestion of meat, control many different reactions, whereas others, such as urease, are extremely specific and may accelerate only one reaction. Still others release energy to make the heart beat and the lungs expand and contract. Many facilitate the conversion of sugar and foods into the various substances the body requires for tissue-building, the replacement of blood cells, and the release of chemical energy to move muscles. Pepsin, trypsin, and some other enzymes possess, in addition, the peculiar property known as autocatalysis, which permits them to cause their own formation from an inert precursor called zymogen. As a consequence, these enzymes may be reproduced in a test tube. As a class, enzymes are extraordinarily efficient. Minute quantities of an enzyme can accomplish at low temperatures what would require violent reagents and high temperatures by ordinary chemical means. About 30 g (about 1 oz) of pure crystalline pepsin, for example, would be capable of digesting nearly 2 metric tons of egg white in a few hours. The kinetics of enzyme reactions differ somewhat from those of simple inorganic reactions. Each enzyme is selectively specific for the substance in which it causes a reaction and is most effective at a temperature peculiar to it. Although an increase in temperature may accelerate a reaction, enzymes are unstable when heated. The catalytic activity of an enzyme is determined primarily by the enzyme?s amino-acid sequence and by the tertiary structure-that is, the three-dimensional folded structure-of the macromolecule. Many enzymes require the presence of another ion or a molecule, called a cofactor, in order to function. As a rule, enzymes do not attack living cells. As soon as a cell dies, however, it is rapidly digested by enzymes that break down protein. The resistance of the living cell is due to the enzyme?s inability to pass through the membrane of the cell as long as the cell lives. When the cell dies, its membrane becomes permeable, and the enzyme can then enter the cell and destroy the protein within it. Some cells also contain enzyme inhibitors, known as antienzymes, which prevent the action of an enzyme upon a substrate. 1. In genetic engineering, scientists use restriction enzymes to isolate a segment of dna that contains a gene of interest, for example, the gene regulating insulin production. 2. A plasmid extracted from its bacteria and treated with the same restriction enzyme can hybridize with this fragment?s ?sticky? ends of complementary dna. 3. The hybrid plasmid is reincorporated into the bacterial cell, where it replicates as part of the cell?s dna. 4. A large number of daughter cells can be cultured and their gene products extracted for human use. [image] Alcoholic fermentation and other important industrial processes depend on the action of enzymes that are synthesized by the yeasts and bacteria used in the production process. A number of enzymes are used for medical purposes. Some have been useful in treating areas of local inflammation; trypsin is employed in removing foreign matter and dead tissue from wounds and burns. Prediction: I predict that when catalase is added to Hydrogen peroxide, the following chemical reaction shall occur: H2O2 [image] 2H2O + O2 Hydrogen [image] Water + Oxygen peroxide I also predict that when you increase the concentration of the hydrogen peroxide, the rate of reaction will increase which will result in faster oxygen production. If I were to draw a graph of the amount of oxygen produced in 5 minutes against the concentration of hydrogen peroxide, I predict that the graph will have a positive gradient and shall have a strong correlation. This is because when you increase the concentration of the solution, you increase the amount of Hydrogen peroxide molecules within the same volume. And because there are more molecules to collide with, the rate of reaction is increased. Equipment: 10vol hydrogen peroxide solution, 20vol hydrogen peroxide solution, 40vol hydrogen peroxide solution, 60vol hydrogen peroxide solution, 80vol hydrogen peroxide solution, Potato corer, 1 Potato, 50ml measuring cylinder, Stop Clock, 11 Boiling Tubes, Tile, Knife. Method: 1. Measure out 30ml of the desired hydrogen peroxide solution and pour these into the boiling tube. 2. Us the corer to take out 4 chips from the potato. 3. Using the tile and the knife, cut the potato chips so that they are all 1cm in length. 4. Check that the gas syringe is at 0cm3. 5. Place the chips into the boiling tube, attach the gas syringe and start the stop clock. 6. Check the readings on the gas syringe every 30 seconds for three minutes and record the results. 7. After the chips have been immersed in the hydrogen peroxide solution for three minutes, remove the gas syringe and reset the stop clock. 8. Repeat the experiment of the desired solutions to gain more accurate results. Safety: When using the knife, be careful not to cut yourself and also be careful when using the hydrogen peroxide as it is irritant. In the event of skin contact, immediately rinse under cold water. Fair Test: To ensure that the experiment goes fairly, I have to control all the factors which could effect the experiment. These factors are: 1. Temperature. 2. Time of immersion. 3. Surface area of the potato chip. 4. Concentration of Hydrogen peroxide. 5. Volume of Hydrogen peroxide. The factor which I am investigating is the concentration of the hydrogen peroxide so this will vary accordingly throughout the experiment. I shall use a constant volume of hydrogen peroxide and I shall also keep the time of immersion constant. I shall use room temperature and shall cut the potato chips to size using a knife and a corer with a constant diameter. Preliminary Results: In order to find suitable concentrations of hydrogen peroxide to use in the experiment, I performed a preliminary experiment. I used a similar method to that of the main experiment except I used 6 chips in the preliminary. Time (mins) 10vol 40vol 80vol 0.5 2 8 4 1 4 11 6 1.5 5 14 7 2 6 16 9 Gas was measured in cm3 From these results I was able to judge a suitable time of immersion. In 2 minutes, 6 chips produced fizz which could have been the cause of the distortion of the results for the 80vol concentration. To avoid this I decided to change the amount of potato chips to 4. But due to this change, the 10vol concentration would produce too less oxygen to take accurate measurements using the gas cylinder and so I shall not use 10vol in the main experiment. To establish a firm conclusion, I will need a wider range of results and so I shall use 20vol and 60vol and I also decided to increase the time to 3 and a half minutes in order to gain a wider range of results. Results: Time (mins) 20vol 40vol 60vol 80vol 1st try 2nd try 1st try 2nd try 1st try 2nd try 1st try 2nd try 0.5 1.00 1.00 2.00 1.50 2.00 2.00 3.00 1.50 1 2.00 1.50 2.50 2.50 3.50 4.00 5.00 3.00 1.5 3.00 2.50 4.00 4.00 4.50 6.00 7.00 4.50 2 4.00 3.50 5.00 5.00 5.00 7.00 9.00 6.00 2.5 5.00 4.50 11.00 6.00 6.00 9.00 11.00 7.50 3 5.50 5.50 11.50 7.00 7.00 10.00 12.50 8.50 3.5 6.50 6.00 13.00 8.00 8.00 11.00 14.00 10.00 Time (mins) 20vol 40vol 60vol 80vol Average Average Average Average 0.5 1.00 1.75 2.00 2.25 1 1.75 2.50 3.75 4.00 1.5 2.75 4.00 5.25 5.75 2 3.75 5.00 6.00 7.50 2.5 4.75 8.50 7.50 9.25 3 5.50 9.25 8.50 10.50 3.5 6.25 10.5 9.50 12.00 All values are rounded to 2dp The gas was measured in cm3 Conclusion: From the graph, you can tell that as the concentration of the hydrogen peroxide increases, the rate of reaction also increases which can be seen through the increasing gradient for each of the higher concentrations. This is because when there are more hydrogen peroxide molecules reacting with a constant volume of catalase enzyme, the rate of reaction increases. Within the graph I detected an inconsistent increase between 2 and 2½ minutes in the line for 40vol. After this the graph continues rising with the expected gradient till the end of the experiment. This inconsistency could be due to a change in temperature but this is unlikely. It is more likely that the reading was taken too late. Although the rest of the graph looks correct, there could be minor errors within the results which were caused by a change in room temperature or human error when taking readings from the gas syringe. Despite this, the results followed the rule of equilibrium which states that the longer the reaction goes on for, the slower it gets. The collision theory states that reactions can only happen when the reactant particles collide, but most collisions are not successful in forming product molecules. The reactant molecules must collide with enough energy to bond so product molecules can be formed. All the rate controlling factors are related to the frequency of reacting particle collision. These factors include temperature, concentration of the dissolved reactants, the surface area of the reactants and the presence of a catalyst. In this experiment, I am investigating the effect of concentration on a reaction. This affects the experiment because a higher concentration results in a higher rate of the reaction, this is because there are more collisions because of the higher number of hydrogen peroxide atoms within the solution. Evaluation: My experiment appears to have been successful as the majority of results appeared correct. Any errors within the experiment would have been due to human error or a change in room temperature. When using room temperature, the temperature could easily change during the experiment and this could easily have changed during the experiment as it was realistically beyond our control. To improve the accuracy of my experiment I could repeat the experiment a few more times and use calipers to get a more accurate measure of the potato chips. From my results it is possible to draw a firm conclusion as the results agree with the rule of equilibrium and the collision theory. Further extensions of this experiment could include leaving the experiment for longer in order to find the exact point of equilibrium, looking at the affects of temperature on the experiment and looking at the affects of changing the surface area of the potato chips. To continue this investigation I could set up an experiment which investigates the affects of the surface area of the potato chips on the rate of the reaction. The experiment would be set up as follows: Prediction: I predict that as you increase the surface area of the potato chips, the faster the reaction will occur. This is because a larger surface area means the hydrogen peroxide has more area to collide with and therefore it will result in more collisions and a faster rate of reaction. Method: Cut potato chips to 1cm, 2cm and 3cm. Set up the apparatus just like the previous experiment and start the stop clock. Take readings every half minute for 3 minutes. Repeat each experiment twice to gain more accurate results.

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