Factors Affecting the Rate of Enzyme Activity Lab

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Factors Affecting the Rate of Enzyme Activity

Justin Hunter
G. Kim
September 16, 2011
September 26, 2011
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.

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.

- 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)

Part 1: Observing a Normal Catalase Reaction (at Room Temperature) 1. 2mL of 3% hydrogen peroxide solution was poured into a graduated cylinder. 2. 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;...
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