This is a lab report I wrote for Biology 1 (Molecular and Cells) class at CCBC Essex in Spring 2009. This report is my work, and cannot be used without my permission. If you have any question(s) about this report or find any errors, please don't hesitate to leave me a comment.

Living organisms produce enzymes to speed up their chemical reactions (Hershey, 2009). The activity of these enzymes can be either fast, slow, or stopped according to the factors influencing them. This experiment tested the effect of different surface areas, temperatures, and pHs on the reaction rate of the enzyme Catalase, as well as the reusability of the enzyme.

Following are the hypothesis:

1. As the surface area gets larger, the reaction rate will increase.
2. The reaction rate will be the fastest when the temperature is at 37°C, and very high temperature (boiling) will denature the enzymes and therefore no reaction will occur.
3. The optimum pH will be 7, and very high pH (pH 10) will denature the enzymes.
4. The enzymes are reusable as long as they are not denatured.

 Materials, experimental setup, and procedures can be found on pages 73 to 78 in the Biology 110 Lab Manual.

Part 1 - Decomposition of Hydrogen Peroxide with the Enzyme Catalase

The enzyme Catalases in two banana wedges with different surface areas were used to test the effect of the surface area on the enzyme activity. One banana wedge was mashed to increase the surface area. O₂ gas was collected using the experimental setup described in the materials and methods section. Results were recorded on Table 1 and graphed on Graph 1.

Part 2 - Effect of Temperature on Enzyme Function

O₂ gas was collected using the experimental setup described in the materials and methods section, the enzyme Catalase in chicken liver, and different temperatures. Different temperatures used were 0°C, room temperature, 37°C, and boiled. The results were recorded on Table 2 and graphed on Graph 2.

Part 3 - Is Catalase Reusable?

The reusability of the enzyme Catalase was tested by pouring unused H₂O₂ over the chicken liver used for previous part. The reusability of H₂O₂ was tested by putting a fresh cut chicken liver in the liquid left from the room temperature test tube from Part 2. The result was negative, no reaction occured.

Part 4 - Reaction Rate of Iced Liver Returned to Room Temperature

The data was collected using the iced liver returned to room temperature. The results were recorded on Table 3.

Part 5 - Effect of pH on Enzyme Activity

The effect of pH on enzyme activity was tested using different pHs (3, 7, and 10). The results were recorded on Table 4 and graphed on Graph 3.

Part 1 – The experiment supported the hypothesis: As the surface area gets larger, the reaction rate becomes faster. It is so because as the surface area gets larger, bigger area gets in contact with the substrate and react to it, therefore speeds up the reaction. An analogy would be there is a long line at the bank, and 5 tellers handles the business faster than 1 teller. The Graph 1 displays a big difference in the reaction rate between mashed banana and whole banana. The mashed banana, the banana with more surface area, has faster reaction rate than the whole banana, the banana with less surface area.

Part 2 – The experiment refuted the hypothesis of 37^oC being the optimal temperature for the enzyme activity (having the fastest reaction rate). This was due to the uncontrolled lab circumstances. Many people were using the incubator and the temperature wasn’t kept stable at 37^oC.

Part 3 – The experiment supported the hypothesis: Catalase was reusable and the hydrogen peroxide wasn’t reusable. Results agree with the established biological facts: reacting substances change, therefore aren’t usable, and enzymes don't change, therefore enzymes are reusable (Hershey, 2009).

Part 4 – The experiment supported the hypothesis: Reaction rate of iced liver returned to room temperature is faster than iced liver. This was so because as long as the enzymes don't get denatured, the enzymes react faster as it gets near the optimum temperature (Brooker, 2008).

Part 5 – The experiment supported the hypothesis: Reaction rate is fastest at pH 7. This was true because the optimum pH for the enzyme Catalase is 7. PH 3 wasn’t close to the optimum pH so the reaction rate was slow, and pH10 was too high and it denatured the enzymes.

Brooker, Robert J, et al. Biology. New York: McGraw-Hill, 2008.

Hershey, James, et al. Biology 110 Laboratory Textbook. New York: Pearson, 2009.