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Enzyme Lab Report

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Category: Science

Autor: reviewessays 25 February 2011

Words: 838 | Pages: 4

AP Biology Lab: Catalase (Enzymes)


In this laboratory exercise, studies of enzyme catalase, which accelerates the breakdown of hydrogen peroxide into water and oxygen. The purpose was to isolate catalase from starch and measure the rate of activity under different conditions. The laboratory was also conducted in association with a second laboratory that measured the effects of an inhibitor on the enzymes.

Changes in temperature and pH along with Substrate Concentration and Enzyme Concentration were the conditions tested in the experiment.

Four AP Biology classes performed this experiment and the data presented in this report will reflect the averages of said classes. In the later discussion sections, it will become very obvious that human error was the deciding factor in the data collection.


Enzymes are biological catalysts that carry out thousands of chemical reactions that occur in living cells. Generally large proteins, enzymes are made up of several hundred amino acids, and often contain a non-proteinaceuos group essential in the actual catalyst.

When an enzyme can on longer function at all, it is said to be denatured. There are several factors that contribute to the denaturing of the enzyme that also determine the enzyme’s shape. These factors are very closely regulated in both living organisms and in laboratory environments, so as to achieve optimum enzyme activity. Temperature of the enzymatic reaction or enzyme itself will help in dictating the activity rate of the function. Likewise is true of the enzymatic reaction’s pH. The other factors include the Substrate Concentration (a substrate is the substance being acted upon) and Enzyme Concentration.

The AP Biology classes performed this study, to examine the effects of changes in the optimum conditions for enzyme activity.


A disc of filter paper was immersed into the enzyme solution for about 15 seconds. Then it was removed from the solution and blotted on a paper towel for 5 seconds. Next the disc was placed in a beaker filled with the hydrogen peroxide substrate and allowed to sink to the bottom of the beaker. The instant the disc hit the bottom, a timer was started. The time measured was that from the time the disc reached the bottom of the beaker until it touched the surface of the hydrogen peroxide. This measurement is that of the activity rate of the enzyme. Finally the procedure was carried out for a second trial.

This procedure was carried out for all four of the conditions being tested and the rates were recorded in respective data tables. An average rate of all four classes, that performed the experiment, was then graphed. Said graphs and data tables are shown in the subsequent section.

Data and Analysis

Rate vs. Enzyme Concentration

2A 3A 4A 4B Average

100 0.081 0.654 0.057 0.13 0.201

80 0.087 0.109 0.043 0.173 0.103

75 0.181 0.057 0.05 0.127 0.104

60 0.095 0.038 0.047 0.111 0.073

50 0.131 0.034 0.041 0.098 0.076

25 0.077 0.014 0.028 0.067 0.047

10 0.064 0.011 0.026 0.042 0.036

0 No Rx No Rx No Rx No Rx No Rx

As the enzyme concentration increased so too did the activity rate. The relatively level areas show where there was substrate depletion.

Rate vs. Substrate Concentration

2A 3A 4A 4B Average

0% No Rx No Rx No Rx No Rx No Rx

0.10% 0.023 0.008 0.01 0 0.01

0.20% 0.025 0.019 0.01 0.011 0.016

0.30% 0.04 0.021 0.014 0.015 0.023

0.50% 0.058 0.018 0.02 0.024 0.03

0.80% 0.041 0.038 0.04 0.035 0.039

1.00% 0.111 0.031 0.042 0.051 0.059

2.00% 0.153 0.095 0.053 0.058 0.09

3.00% 0.136 0.092 0.067 0.103 0.1

As the substrate concentration increased so too did the activity rate in an almost linear fashion.

Rate vs.pH

2A 3A 4A 4B Average

NaOH - 12 0.16 0.09 0.062 0.15 0.12

Malox - 9 0.22 0.13 0.057 0.13 0.13

Hydrogen Peroxide - 7 0.17 0.16 0.062 0.16 0.14

Vinegar - 3 0.1 0.19 0.051 0.11 0.11

HCL - 1 0.09 0.24 No Rx 0.1 0.108

The rate peaked at a pH of 7 and then decreases outward.

Rate vs. Temperature

2A 3A 4A 4B Average

0 degrees C 0.67 0.09 0.66 0.18 0.4

5 degrees C 1 0.13 0.84 0.13 0.46

25 degrees C 0.5 0.16 0.02 0.22 0.11

40 degrees C 0.22 0.19 0.19 0.1 0.18

60 degrees C 0.33 0.24 0.05 0.08 0.175

At the lower temperatures, the activity rate was high but then at 25oC, the rate dropped. After that the rate seems to be increasing toward another drop-off point.

Inhibitor Effects

2A 3A 4A 4B Average

Control 0.2 0.095 0.52 0.115 0.23

Hydroxylamine 0.0083 0.001 0.008 0.004 0.005

The inhibitor slowed the reaction to almost a complete stop.


In conclusion, the classes have come to the result that each enzyme has a specific set of conditions that must be met for optimum activity. The changes in the temperature, pH, substrate concentration and enzyme concentration, cause fluctuations in the activity rate of the enzyme. Also, if the temperature or pH is too high or too low, then the enzyme will denature and be worthless to the organism or experiment.


The primary class, 4A, found that our results differed greatly from the other classes. Not to sound presumptuous, however the only valid explanation for the differences is human error in carrying out the given procedures. Whether the timing was off or the instructions were just not followed, the fact still remains that certain classes did not get good data for this experiment.