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Catalase investigation

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CATALASE INVESTIGATION PLANNING SECTION Introduction This investigation aims to determine the effect that varying the pH of the conditions in which a reaction between an enzyme and a substrate takes place. In particular the reaction of hydrogen peroxide being broken down into water and oxygen by an enzyme, catalase. 2H2O2 --> 2H2O + O2 This reaction would normally occur naturally, but in the presence of the enzyme catalase the reaction occurs much more rapidly and vigorously. Enzymes An enzyme is a biological catalyst. A catalyst can be defined as; a substance that increases the rate of a chemical reaction by reducing the activation energy, but which is left unchanged by the reaction. There are more than 1500 known enzymes today, each one specific to its substrate. An enzyme is any one of many specialised organic substances, composed of polymers of amino acids, which act as catalysts to regulate the speed of the many chemical reactions involved in the metabolism of living organisms. There are 6 major classes of enzymes: 1. Oxidoreductases which are involved in oxidation, reduction, and electron or proton transfer reactions; 2. Transferases, catalysing reactions in which groups are transferred; 3. Hydrolases which cleave various covalent bonds by hydrolysis; 4. Lyases catalyse reactions forming or breaking double bonds; 5. Isomerases catalyse isomerisation reactions; 6. Ligases join substituents together covalently. However, how they are classed depends on what kind of reaction they control. Many other enzymes control many other different kinds of reactions. Most enzymes are named by adding "ase" on the end of the substrate which they break down. For example enzymes specific to protein are called "proteases", similarly the enzyme that controls urea decomposition is called "urease". However, some enzymes retain their names from before this method of naming came into use. Amylase, the enzyme that breaks down starch, is a good example of this, as are pepsin and trypsin. ...read more.


When the pH reaches a certain point it will be at the catalase's optimum pH and will work at maximum efficiency. However, once the pH exceeds this level the rate of reaction will start to drop until finally, when the pH passes a certain point, the rate of reaction will be zero, meaning the enzyme will cease to function. OBTAINING EVIDENCE SECTION Here are the results I obtained from the experiment: Amount of H2O2 (ml) Buffer Soln. (pH) Amount of Buffer Soln. (ml) Vol. Of Oxygen Produced (cm3) Time Limit (mins) Mass Of Liver (g) Mass Of Weighing Boat (g) 5 2 5 8 2.5 2.62 3.8 5 2 5 9 2.5 2.53 3.8 5 2 5 13 2.5 2.46 3.8 5 4 5 8 2.5 2.47 3.8 5 4 5 26 2.5 2.55 3.8 5 4 5 23 2.5 2.53 3.8 5 6 5 26 2.5 2.53 3.8 5 6 5 15 2.5 2.51 3.8 5 6 5 25 2.5 2.47 3.8 5 8 5 22 2.5 2. 46 3.8 5 8 5 23 2.5 2.48 3.8 5 8 5 20 2.5 2.51 3.8 5 10 5 24 2.5 2.52 3.8 5 10 5 27 2.5 2.50 3.8 5 10 5 29 2.5 2.56 3.8 I can now use these results from the table to calculate the average volumes of oxygen produced: Amount of H2O2 (ml) Buffer Soln. (pH) Amount of Buffer Soln. (ml) Average Vol. Of Oxygen Produced (cm3) Time Limit (mins) Average Mass Of Liver (g) Mass Of Weighing Boat (g) 5 2 5 10 2.5 2.54 3.8 5 4 5 19 2.5 2.52 3.8 5 6 5 22 2.5 2.50 3.8 5 8 5 22 2.5 2.48 3.8 5 10 5 27 2.5 2.53 3.8 ANALYSING EVIDENCE SECTION Processing the Results I can now use this data to plot a graph of volume of oxygen produced against pH buffer solution. This will show me how the enzyme activity, i.e. the amount of oxygen produced by catalase, changes with increasing temperature. ...read more.


Thus showing how the reaction is affected by maximum surface area exposure. I could repeat the experiment more than three times each, perhaps five or even ten. This would make my results even more accurate, enabling me to make an even more accurate conclusion on the subject. Similarly I could allow more time for the experiments and more amounts of pH buffer and hydroxide, making the results larger and so minimising error. I could compare my results with those of books, or other experiments like mine. This would allow me to see whether my results were genuine or whether they were actually meant to follow another trend. The internet could be used to obtain other sources of data for these experiments, allowing me to compare my own results with others again. To increase the scope of the investigation I could try using different enzymes with their own specific substrates. I would be quite interested to see if the case with my investigation's enzyme was the same with all enzymes. I would also help me with my scientific reasoning as it would give me more information to use as examples and proof. I could also try using different temperatures and different concentrations of substrate and enzyme. This would help me with other investigations I might do, or would help me in leaning more about enzymes and how they work under different conditions. Conclusion In all this experiment, in my mind has been very successful and rewarding. It has taught me more about enzymes, the tertiary makeup etc. and has as a result furthered my biological knowledge on this area. I have been able to prove that as pH increases so does enzyme activity and that it peaks at a point. However I was unable to prove that the activity decreases after the peak. But I still believe it to be true and that if I had the opportunity I would redo certain parts of this experiment in order to ensure that I could prove that fact, however, overall a very successful investigation. ...read more.

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