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By completing this lab about enzyme activity, the knowledge about the five main factors that affect the rate of enzyme activity was easier to comprehend. Before understanding those concepts, it's crucial to understand the background information of the molecules involved with this lab. In order to have a larger perception of the lab and a better understanding of why it was done, one must interpret the general functions of enzymes and catalase.
There are many substances found in human bodies that help different organisms function properly. One important substance that is found in human bodies is called an enzyme. An enzyme is a protein-based protein that acts like a catalyst, which is a substance that speeds up a chemical reaction without being effected, in the reactions within the body (Wise Geek). For example, the enzyme found in saliva breaks down the food in order for it to digest in the body. Without this enzyme, it would take weeks for the body to digest the food by itself (Wise Geek).
The way that enzymes work is easy to visually distinguish. When two molecules react with one another, they must connect in some way. The molecules have to collide in the right orientation and with enough sufficient energy, meaning that the energy between the molecules must be present, for the collision to occur. This type of energy is called the activation energy. A part in an enzyme that has the specific shape and functional groups to join to one of the reacting molecules is the active site. When the enzyme attaches to a specific substrate, the reactants of the reaction, this is when the enzyme speeds up the process and the binding of the substrate and enzyme is called an enzyme-substrate complex (Bright Hub).
Catalases are enzymes that are commonly present in most living organisms and are very strong catalysts. Catalase helps the body break down hydrogen peroxide, a harmful oxidizing agent found in the body, into oxygen and water. This prevents the buildup of carbon dioxide bubbles in the blood stream (eHow). The cellular function of a catalase is like the function of white blood cells in the body; the white blood cells battle viruses in human bodies while catalase battles the effect of free radicals in the body. Free radicals are unstable molecules found in the body that make other molecules very unstable and can damage proteins, cell membranes and DNA structure. Thus, catalase battles against the effect of these molecules by transforming them into hydrogen peroxide, and then later breaking it into oxygen and water (eHow).
There are many types of enzymes, including anabolic and catabolic enzymes, and the reactions that are accompanied with them. Anabolic reactions are involved with creating large molecules out of smaller molecules and catabolic reactions break down large molecules into smaller molecules (Nelson Biology 12). The activation energy in any type of reaction lowers due to the catalysts that can be found in the reactions. Enzymes play an important role in terms of lowering activation energy and aren't consumed by the reaction (Nelson Biology 12).
However, there are five main factors that affect the activity of enzymes, whether it's positive or negative. These five factors are the reasons due to the completion of this particular lab and the information that is gathered about these factors give further knowledge of why each factor occurs. The five main factors are: change in enzyme concentration, temperature, pH, substrate concentration and the addition of an inhibitor.
From the information about enzymes and catalase provided, it will now be easier to understand the basis of this lab. The point of this lab was to figure out how different environmental conditions would affect the activity of the enzyme. With the provided information in mind, the reasoning behind the results of this lab will further be interpreted and the factors that affect enzyme activity will be easier to understand.
Analysis: Trends and Patterns
The trends and patterns that were found during this experimental lab are all intertwined with one another and help one understand more about enzyme activity. Even though there are five separate factors that affect enzyme activity, they are all connected in some way and the provided data shows this connection.
Table 1: Change in enzyme concentration
Enzyme concentration & compositions
Rate of Change (cm/s)
100 % concentration (10 mL potato juice)
- bubbles appeared
80 % concentration (8 mL potato juice, 2 mL distilled water)
- fewer bubbles than previous composition
60 % concentration (6 mL potato juice, 4 mL distilled water)
- fewer bubbles than previous composition
40% concentration (4 mL potato juice, 6 mL distilled water)
- fewer bubbles than previous composition
20% concentration (2 mL potato juice,
- no bubbles appeared
Figure 1: Change in enzyme concentration
Factor 1: Change in enzyme concentration
The pattern that was determined from this part of the lab was that the larger the amount of enzyme concentration, which is the amount of potato juice, the more the rate of change increased. The lower the enzyme concentration, the rate of change decreased.
Table 2: Change in temperature
Figure 2: Change in temperature
Factor 2: Change in temperature
The pattern that was found in this part of the lab was that the temperature of 35°C was the optimal temperature throughout this experiment and was the temperature at which the rate of change was at its highest point. This means that when the temperature was either higher or lower than 35°C, the rate of change would decrease.
Table 3: Change in pH
Amount of H2O2 (mL)
Amount of Distilled Water (mL)
Amount of pH Buffer (mL)
Vertical Distance Travelled by Filter Paper Towards Meniscus
Time taken by filter paper disc to move to meniscus (s)
Upward velocity of Filter Paper Disc (cm/s)
Figure 3: Change in pH
Factor 3: Change in pH
The pattern that was found for this part of the lab relates with the part of the lab that was previously mentioned, change in temperature. The pH level of 7 was the control (optimal pH value) and any pH lower or higher than 7, the rate of change would decrease.
Table 4: Change in substrate concentration
H202 of Distilled Water
Time of catalase to travel from the bottom of the test tube to the top (s)
Distance of bottom of test tube to substrate(cm)
Rate of change of the catalyzed reaction (cm/s)
15 mL of H202
13 mL of H202 2.6%
10 mL of H202 2%
7.5 mL of H202 1.5%
5 mL of H202 1%
Figure 4: Change in substrate concentration
Factor 4: Change in substrate concentration
The pattern that was observed in this part of the lab was very similar to Factor 1: Change in enzyme concentration. The higher the percentage of substrate concentration (H202 concentration), the more increased the rate of change was.
Table 5: Addition of an Inhibitor
Amount of Inhibitor (copper (II) sulfate drops)
Rate of change (cm/s)
Figure 5: Addition of an Inhibitor
Factor 5: Addition of an Inhibitor
The pattern that was found in this part of the lab involved inhibitors, chemicals that block active sites on enzymes. The larger the amount of inhibitor (copper II sulfate) that was added to the enzyme concentration, the slower the rate of change was.
Before conducting the lab, certain hypotheses were made for each factor that affects enzyme activity. Based on the knowledge that was already given about enzymes, the hypotheses that were made were the best to represent what was predicted to occur in each part of the lab.
For Part 1: Change in enzyme concentration, if the enzyme concentration was decreased in an H202 decomposition reaction, then the rate of change will also decrease. This hypothesis was made based on this part of the lab because if the composition wasn't pure enzyme solution, it would affect the rate of change. This hypothesis was proved according to Table 1: Change in enzyme concentration; the 20% concentration of potato juice (2 mL potato juice and 8 mL distilled water) had the lowest rate of change value. This composition was the one that had the least amount of enzyme solution; this composition only had 2 mL of enzyme concentration. This connects with the hypothesis because the lower the enzyme concentration, the lower the rate of change. Also, at a low enzyme concentration, there is a great amount of active sites and the rate of the reaction is low. As the enzyme concentration increases, there are more active sites and thus, the reaction will precede faster (S-Cool). Therefore, the overall trend that was portrayed in this part of the lab was that as the concentration of the enzyme increased, the rate of change also increased.
For Part 2: Change in temperature, if the temperature was higher or lower than 37 °C, which is the optimal temperature in living organisms (Nelson Biology 12), then the rate of change would decrease. This hypothesis was correct except for one characteristic: the optimal temperature in this part of the lab was 35°C instead of the normal optimal temperature in organisms which is 37°C. The rest of the hypothesis was accurate since when the temperature that was either higher or lower than 35°C, the rate of change decreased. When the temperature was higher than the optimal temperature, this was due to the denaturing of the solution. When the temperature was lower than the optimal temperature, this was caused due to the short amount of kinetic energy required for the reaction to occur faster (RSC).
Referring to Figure 2: Change in temperature, when the temperature was either higher or lower than the optimal temperature, the rate of change would decrease. In other words, as the temperature rises, the molecules that were reacting would have more kinetic energy. Since the molecules have more energy, this would increase chances of collisions between the molecules and therefore would increase the rate (RSC). This data correlates with the hypothesis because when the optimal temperature was not reached, the rate of change was decreased. The overall trend that was determined for this part of the experiment was that if the temperature was higher or lower than the optimal temperature (35°C), the rate of change would decrease.
Regarding Part 3: Change in pH, if the pH (optimal pH is 7) was higher or lower than the optimal pH, the rate of change would decrease. This hypothesis was proved to be right because when the pH was either 2, 4, 9 or 12, the rate of change would be lower than the rate of change at the pH of 7. This hypothesis is connected to the hypothesis in Part 2: Change in temperature because they both have the same characteristics when it comes to affecting enzyme activity. Referring to Table 3: Change in ph, when the pH value was either higher or lower than 7, the rate of change would decrease. Similarly with the change in temperature, changes in the pH value would make but also break intermolecular and intramolecular bonds. By changing the bonds, this would also change the shape of the enzyme and change the enzymes efficiency (RSC). Thus, when the optimal pH is not being used, the rate of change will be decreased due to denaturing of the enzyme (Nelson Biology 12). The general trend that was found in this part of the lab relates to Factor 2: Change in temperature, as they both share the same characteristics in the terms of the given data. The higher or lower the pH value was from the optimal pH value, the rate of change would be decreased.
For Part 4: Change in substrate concentration, if the substrate concentration was increased in a decomposition reaction with catalase, the rate of change would also increase. This hypothesis was accurate because when the highest concentration was used, 3%, the rate of change was also the highest, 1.27 cm/s. Since there was more substrate solution, H202, the rate of change was also the highest out of all the other concentrations. Referring to Figure 4: Change in substrate concentration, this figure is similar to Figure 1: Change in enzyme concentration because as the concentration increased, so did the rate of change. The overall trend that was found in this part of the lab was similar to Factor 1: Change in enzyme concentration from the provided data. Relating to the active sites in terms of the rate of the reaction, when the substrate concentration is low, this means that there are less active sites being occupied and this also means that the rate of change is also low. When more substrate molecules are added, additional enzyme-substrate complexes are formed. Therefore, as there is a bigger amount of active sites, the rate of change increases (S-Cool). In other words, as the concentration of the substrate solution is increased, the rate of change also increased.
For Part 5: Addition of an Inhibitor, if the amount of the inhibitor was increased, the rate of change would decrease. This hypothesis was also correct because based on the knowledge already known about inhibitors, it was clear that the more inhibitor that is put into a solution, the slower the solution would react. The inhibitor in this case was the copper II sulfate and this hypothesis was accurate because the more drops of copper II sulfate that was added to the enzyme solution, the more the rate of change decreased. Since an inhibitor is meant to block active sites of enzymes, this characteristic would affect the rate of change and make it decrease. There are two types of inhibitors: competitive and noncompetitive inhibitors. Competitive inhibitors penetrate into the enzyme's active site and block the substrate form binding. Noncompetitive inhibitors join to another site on the enzymes which creates a change in the enzyme's shape. The change in shape causes lose of resemblance for the substrate (Nelson Biology 12). In other words, as more inhibitor is added, the availability of active sites decreased since the inhibitors block normal substrates from binding and changes the shape of the enzyme.
The hypotheses that were made for each part of the lab came to be correct based on the information provided about factors affecting enzyme activity. Each hypothesis was proved by the data that is provided in the Analysis: Tables & Figures and that also give a visual representation of each hypothesis.
Evaluation: Sources of Error
Not every experiment is absent of errors but by observing these errors, experiments can be done more accurately in the future. There were many errors that were found throughout the lab; however these specific sources of errors are the ones that were sources of errors rather than human errors.
Inconsistency of pushing the filter paper down in a test tube- after dipping the filter paper into the enzyme solution, the filter paper had to be pushed down to the bottom of the test tube with the substrate solution. One important aspect of the lab was to time how long the filter paper took to rise back to the top of the meniscus of the solution. However, pushing the filter paper to the bottom of the test tube was inconsistent each time it was done. To improve this error in the future, other materials could have been used to assist the filter paper to go right to the bottom of the test tube rather than floating back to the top, such as materials like a scoopula or any other material that is long in length.
Test tubes measurements - for each part of the lab, the measurement of the enzyme and substrate solutions were made and poured into a test tube. Even though the volume of the solution was easy to determine by using a graduated cylinder, the length (distance) of the solution was inaccurately measured. The use of a ruler made the measurements of the solution imprecise and was an occurring source of error for each part of the lab.
Amount of inhibitor in the solution - For Part 5: Addition of an Inhibitor, the copper (II) sulfate was dropped into the test tube as the inhibitor and this part of the experiment was inconsistent due to the amount of inhibitor that was released into a solution each time. A dropper isn't a reliable piece of material in this lab due to the fact that it may take more inhibitor at one time and a less amount the next time.
These three main errors that were made during this part of the lab could have been avoided if more attention and detail was put into the experiment. However, errors that occur during an experiment are what make experiments worth doing over again; to compare results and understand why something was done wrong.
Evaluation: Next Steps
To every type of problem, there are always different approaches one can take. For this particular lab, understanding the factors that affect the rate of enzyme activity, there are other ways that can determine the effect of these factors.
Potential Experiment #1:
For Part 2 and 3 in this lab, the optimal temperature and pH level were determined during the experiment. However, for Part 1, 4, and 5, the optimal concentrations for the substrate, enzyme or inhibitor concentrations weren't determined. Another way to carry out this experiment that would ensure new information would be to find out the optimal concentrations for the substrate, enzyme and inhibitor. By finding these concentrations, new information about enzyme activity can be determined and compared to the data that is already known about factors that affect enzyme activity.
Potential Experiment #2:
The substrate in this lab that was used was hydrogen peroxide, the substance that is provided from the decomposition of catalase. Another way of conducting this experiment could be to use another type of enzyme, like maltose. Maltose is another important enzyme because it is an enzyme that catalyzes the hydrolysis of maltose to glucose (Answers). Every enzyme has different characteristics and by conducting this specific lab with a different enzyme, the characteristics can be determined. Using a different substrate molecule could be a way to further extend the knowledge about enzyme activity.
These two potential experiments for the lab based on the factors that affect enzyme activity can be used to further understand the concept of enzyme activity. By using these different experiments, the information that is gathered can be used to further educate and show how diverse enzyme activity can be.
Evaluation: Closing Thoughts
Even though the point of this lab was to determine how changes in substrate and enzyme concentration as well as environmental changes such as pH and temperature affect enzyme activity, a lot more information was learned throughout the process of the lab. The information for each factor was learned thoroughly and the basis of why each part was done was also determined. Since this lab wasn't particularly precise in some ways, other potential experiments were thought out and can be used to further extend the knowledge of enzyme activity. By learning about enzymes in class, as well as conducting this specific lab, the knowledge about biological catalysts was extended and can be connected to situations that occur daily.