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Factors Affecting the Rate of Enzyme Activity Justin Hunter G. Kim September 16, 2011 September 26, 2011 Abstract Catalase is a common??enzyme??found in nearly all living organisms that is frequently used by cells to rapidly catalyze the??decomposition of hydrogen peroxide into less reactive oxygen??and water molecules. Catalase is a protein that is most commonly found in the liver. The purpose of this experiment was to determine the effect that changes in temperature and pH have on the function of the enzyme catalase. Five test tubes were collected and cleaned.
The first was used as a control and the effects of a normal catalase reaction at room temperature were recorded. The speed of the reaction was rated on a scale of 0-5, with 5 being a very fast reaction and 0 being a very slow reaction (This scale was also used to rate the rest of the reactions in this experiment). The second and third test tubes were used to determine the effects of a catalase reaction at a high temperature and a low temperature, respectively. The fourth test tube was filled with HCl to make it acidic and the fifth test tube was filled with NaOH to make it basic.
Five pieces of fresh liver were cut and each piece was placed in a separate tube. The reactions were rated and recorded. It was found that if an enzyme is exposed to high temperatures, the rate of enzyme activity would increase but only up to a certain point. When it reached this point, the enzyme would start to denature. This also held true for when an enzyme was taken too far out of its pH range. When exposed to extremely low temperatures, the enzyme would not denature but the rate it catalyzed reactions would decrease instead. Thus it was concluded that an enzyme functions best when not exposed to extreme temperatures or pH levels.
Introduction The chemical reactions occurring in the liver are controlled by catalase. This experiment tested the effect of different temperatures, and pH’s on the reaction rate of the enzyme catalase. It was hypothesized as follows: 1. An increase in temperature will induce a faster reaction. 2. A decrease in temperature will induce a slower reaction. 3. An increase in pH will result in a slower reaction. 4. A decrease in pH will result in a slower reaction. An increase in temperature results in more kinetic energy between molecules.
The molecules will experience an increase in collisions and thus the rate at which the enzyme performs will also increase. A decrease in temperature will reduce this kinetic energy and the speed at which the substrate and enzyme collide which will result in less successful collisions. Changes in pH may change the shape of the enzyme which would leave the substrate unable to bind to the active site, thus reducing the overall rate of enzyme activity. The hydrogen peroxide was kept away from the hot plate as hydrogen peroxide is flammable. Beaker tongs and test tube holders were used when handling heated glassware.
Gloves and goggles were to be worn at all time during the lab as hydrogen peroxide is corrosive. Materials – 40mL 3% hydrogen peroxide (H2O2) solution – scalpel – scoopula – forceps/tweezers – stirring rod – pH paper – fresh liver – 6 test tubes – test tube rack – 10mL graduated cylinder – 50mL graduated cylinder – hot plate – 250mL beaker – thermometer – test tube tongs – beaker tongs – 0. 1M HCl (Hydrochloric Acid) – 0. 1M NaOH (Sodium Hydroxide) Procedure Part 1: Observing a Normal Catalase Reaction (at Room Temperature) 1. 2mL of 3% hydrogen peroxide solution was poured into a graduated cylinder. . A small piece of liver was cut, by the use of forceps and scalpel, and dropped in the test tube. A stirring rod was used to push the liver into the test tube. 3. 2mL of 3% hydrogen peroxide solution was poured from a graduated cylinder into the test tube. 4. The speed of the reaction was rated on a scale of 0-5 (0 = no reaction; 3 = moderately fast reaction; 5 = very fast reaction). 5. Observations were recorded in the observation table. Part 2: Examining the Effect of Increasing Temperature on Catalase Activity 1. 100mL of water was poured into a 250mL beaker.
The beaker was placed on a hot plate and the water was heated until it began to boil. 2. A small piece of liver was dropped into a test tube and was covered with a small amount of water. 3. The test tube with the liver sample was placed in the boiling water bath for 2 minutes. 4. The test tube containing the liver was removed from the hot water by a test tube holder. The hot plate was turned off. 5. 2mL of 3% hydrogen peroxide solution was poured into the test tube. 6. The speed of the reaction was rated on a scale of 0-5. 7. Observations were recorded in the observations table.
Part 3: Examining the Effect of Decreasing Temperature on Catalase Activity 1. A small piece of liver was dropped into a test tube and covered with a small amount of water. 2. The test tube containing the liver sample was placed in an ice water bath for 2 minutes. 3. The test tube containing the liver sample was removed from the ice water bath by a test tube holder. 4. 2mL of 3% hydrogen peroxide was poured from a graduated cylinder into the test tube. 5. The speed of the reaction was rated on a scale of 0-5. 6. Observations were recorded in the observations table. Part 4: Examining the Effect of pH Changes on Catalase Activity 1. mL of 3% hydrogen peroxide was added to 2 test tubes. A piece of masking tape was used to label the tubes #1 and #2. 2. HCl was added to test tube #1, 1 drop at a time, until the pH reached a level of 2-3; pH paper was used to determine the pH of the solution. 3. A small piece of liver was dropped into the test tube. 4. The speed of the reaction was rated on a scale of 0-5. 5. Observations were recorded in the observations table. 6. NaOH was added to test tube #2, 1 drop at a time, until the pH reached a level of 10; pH paper was used to determine the pH of the solution. 7. A small piece of liver was dropped into the test tube. . The speed of the reaction was rated on a scale of 0-5. 9. Observations were recorded in the observations table. Part 5: 2nd Trial 1. Parts 1-4 were repeated for a second trial. Observations 1st Trial Part 1: Observing a Normal Catalase Reaction (at Room Temperature)| Temperature| Rate| Analyses| Room Temperature| 4| – Fizzes right when you put in H2O2- Bubbles and Foam present-Bubbles and Foam climb halfway up the tube| Part 2: Examining the Effect of Increasing Temperature on Catalase Activity| Temperature| Rate| Analyses| 870F| 5| – Fizzes right when you put in H2O2- Bubbles more than Control and climbs ? f the way up the tube| Part 3: Examining the Effect of Decreasing Temperature on Catalase Activity| Temperature| Rate| Analyses| 10C| 3| – Fizzes right when you put in H2O2- Bubbles less than Control – Reaction occurs, but very slow-Bubbles barely reach ? of the test tube| Part 4: Examining the Effect of pH Changes on Catalase Activity| pH| Rate| Analyses| 2-3| 2| – Fizzes right when you put in H2O2- Bubbles less than Control – Reaction occurs, but very slow-Bubbles disappear after a while| Part 4: Examining the Effect of pH Changes on Catalase Activity| pH| Rate| Analyses| 0| 2| – Fizzes right when you put in H2O2- Bubbles less than Control – Reaction occurs, but very slow(still faster than pH 2-3)-Bubbles disappear after a while| 2nd Trial Part 1: Observing a Normal Catalase Reaction (at Room Temperature)| Temperature| Rate| Analyses| Room Temperature| 4| – Fizzes right when you put in H2O2- Bubbles and Foam present-Bubbles and Foam climb a little bit less than halfway up the tube| Part 2: Examining the Effect of Increasing Temperature on Catalase Activity| Temperature| Rate| Analyses| 870F| 5| – Fizzes right when you put in H2O2- Bubbles more than Control and climbs ? f the way up the tube| Part 4: Examining the Effect of pH Changes on Catalase Activity| pH| Rate| Analyses| 2-3| 1| – Fizzes right when you put in H2O2- Bubbles less than Control – Reaction occurs, but very slow (slower than pH 10)-Bubbles disappear after a while| Part 4: Examining the Effect of pH Changes on Catalase Activity| pH| Rate| Analyses| 10| 2| – Fizzes right when you put in H2O2- Bubbles less than Control – Reaction occurs, but very slow (still faster than pH 2-3)-Bubbles disappear after a while| Discussion The experiment supported the first hypothesis: An increase in temperature will induce a faster reaction.
This was due to the increased kinetic energy of the substrate and enzyme molecules. The number of successful collisions between the enzyme and the substrate increased and thus the enzyme was able to catalyze reactions much more quickly. This would explain why the froth had reached ? of the test tube: There were an increased number of catalyzed products. It would also explain why the froth stopped at only ? of the tube: “Although an increase in temperature increases the rate of most reactions, proteins are denatured at high temperatures and lose their function. ” (Di Giuseppe et. Al, 2003, p. 9). The experiment also supported the second hypothesis: A decrease in temperature will induce a slower reaction. Since the kinetic energy of the molecules is greatly lowered, the number of collisions the substrate and the enzyme will experience is also greatly lowered. Thus the rate at which the enzyme will catalyze the reactions is also lowered. The experiment did not support the third hypothesis: An increase in pH will result in a slower reaction. This is because, though the reaction that took place was slow, it was still faster than the reaction that took place in the lower pH.
As pH increases, enzyme activity increases until it reaches an optimal point at which the enzyme denatures. At this point, the shape of an enzyme’s active site is distorted which renders the substrate incapable of docking to the active site. This explains why the bubbles in the test tube had disappeared. The enzyme still showed signs of a reaction, because it was not taken too far out of its pH range. The experiment supported the fourth hypothesis: A decrease in pH will result in a slower reaction. A pH of 2-3 was not close to the optimum pH so the reaction rate was slow.
Since the enzyme was taken too far out of its pH range, it became distorted and was incapable of catalyzing any reactions. The optimum pH for catalase is 7. This is because the??catalase enzyme??needs to be able to work efficiently in our body. Catalase is in most of our??organs, and most of our body has a pH of 7. For catalase to work most efficiently in our body, it should work best at whatever the pH of the body is. Furthermore, most of the human body is composed of water and the pH of water is 7. In order for the enzyme to work efficiently with the rest of our body, its pH would also have to be 7.
Altering the enzyme concentration would also help the enzyme work much more efficiently in our bodies. More enzymes would ensure an increased rate of catalyzed reactions within our body however, further experimentation would be required. Conclusion In conclusion, three of the four hypotheses were proved correct. Enzyme activity increases and decreases with the temperature. This is due to the increase and decrease of speed in the kinetic energy of the enzyme and substrate molecules. The enzymes can only be heated up to a certain point, because after it reaches this point the enzyme will start to denature.
Enzyme activity increases with pH up to an optimum point. When it reaches this level, the enzyme will start to denature and enzyme activity will cease to exist. However, enzyme activity will decrease as the pH is lowered. The further away an enzyme is taken away from its optimal pH level, the quicker it will start to denature. References “Catalase – An Extraordinary Enzyme. ” Catalase Home Page. Web. 24 Sept. 2011. <http://www. catalase. com/cataext. htm>. Di, Giuseppe Maurice. Nelson Biology 12. Toronto: Nelson Thomson Learning, 2003. Print. Dugdale, David C. Enzyme: MedlinePlus Medical Encyclopedia. ” National Library of Medicine – National Institutes of Health. Web. 24 Sept. 2011. <http://www. nlm. nih. gov/medlineplus/ency/article/002353. htm>. “Effects of PH (Introduction to Enzymes). ” Enzymes, Biochemicals: Worthington Biochemical Corporation. Web. 24 Sept. 2011. <http://www. worthington-biochem. com/introbiochem/effectspH. html>. “Temperature Effects (Introduction to Enzymes). ” Enzymes, Biochemicals: Worthington Biochemical Corporation. Web. 24 Sept. 2011. <http://www. worthington-biochem. com/introbiochem/tempeffects. html>.