Abstract: Enzymes, molecules that speed up chemical reactions, are specific to one substrate. In this experiment the substrate hydrogen peroxide and the enzyme catalase will be used. The higher the concentration of potato extract, or catalase, the faster the reaction and the more substrate present will result in a decrease in the time of the reaction. The amount of concentrations of enzymes and substrates are changed to determine if the reaction is further catalyzed by a greater concentration of enzymes or substrates.
The result of the experiment will show the relationships between the concentration of enzymes and the time of the reaction and the concentration of the substrate and the time of the reaction. Introduction: Enzymes are molecules that act as catalysts to chemical reactions in the body. These enzymes are made by cells and can be used over and over. Each enzyme has a specific functions that carry out the reactions necessary for life. The DNA in cells codes all the information necessary to make many different enzymes and they are produced using this code whenever the cell feels the need for a particular enzyme.
Enzymes are very specific, meaning that there are certain ones made to act on and recognize certain substrates, or the molecules on which an enzyme acts. These enzymes are specific because they are each folded into a specific shape, within the folds of the shapes is an active site, or the site where the reaction takes place. It is important to understand that enzymes are very sensitive and are influenced by pH, temperature, the concentration of the enzyme, and the concentration of the substrate. If an enzyme’s pH or temperature is too high or too low, the enzyme may not work.
For this experiment, the enzyme catalase will be used. Catalase is used to break down the substrate hydrogen peroxide, a poison. The lab will require a catalase, found in potatoes, and hydrogen peroxide. The goal of this experiment is to measure the catalase activity. The higher the concentration of potato extract, or catalase, the faster the reaction and the more substrate present, the faster the reaction. Materials and Methods: The potato extract, or catalase, was made by cutting clean potatoes into chunks, placing them in a blender, and adding 200 ml of buffer per potato.
Next, the potato chunks and buffer were pureed in the blender and poured through four layers of cheesecloth placed in a funnel. Finally, the final volume of potato puree was brought up to 200 ml per potato by adding the necessary amount of distilled water and swirled in the flask to mix the solution. The first part of the experiment where the concentration of catalase was altered began by preparing the enzyme concentrations in the 100 ml beakers and labeling them based on the enzyme concentration: 20%, 40%,60%, 80%, and 100%.
The appropriate dilutions were made based on the chart. For example, 8 ml of potato extract was measured using a graduated cylinder and poured into the beaker for test number one. Next, the graduated cylinder, used for measuring the amount of water and extract, was rinsed and 32 ml of distilled water added and stirred with a stirring rod. After obtaining a flask of 1% hydrogen peroxide solution, 30 ml of that solution was poured into a clean beaker and labeled “reaction beaker.
To begin the measuring the effects of enzyme concentration on enzyme activity, one paper disk was picked up using clean forceps and dunked into the enzyme extract for five seconds and drained on a piece of paper towel for five seconds. Next, that same filter disk containing enzyme extract was placed onto the bottom of the 200 ml “reaction beaker”, containing 1% hydrogen peroxide solution. The time needed for the filter paper to float to the top from the bottom of the reaction beaker was measured using a stopwatch and recorded. The disk was emoved and discarded and the same steps were repeated two additional times using another, clean disk.
The three amounts of time were averaged and recorded and finally, the procedure was repeated for all five enzyme concentrations and the work area was cleaned up. The second part of the experiment where the hydrogen peroxide concentrations were varied began by labeling clean beakers with the percent of hydrogen peroxide used: 2%, 1. 5%, 1. 0%, 0. 8%, 0. 6%, and 0. 3%, then the particular substrate concentrations were prepared in each of the labeled beakers.
For example, 20 ml of hydrogen peroxide was measured in a graduated cylinder and poured into a beaker, then the graduated cylinder was rinsed out and 10 ml of distilled water was measured using the same graduated cylinder and poured into the same 100 ml beaker. The solutions were stirred and the steps for part two were repeated using different volumes of water and hydrogen peroxide, as shown on the table. All the 100 ml beakers were placed on the table from lowest to highest concentration of hydrogen peroxide.
The 60% catalase solution was obtained and a disk was dipped, using forceps, into the 60% potato solution for five seconds. The disk was drained on a paper towel for the same amount of time, then placed on the bottom of the reaction beaker containing the various percentages of hydrogen peroxide. The amount of time it took for the disk to rise to the top of the solution from the bottom was timed using a stopwatch and recorded. The steps were repeated three times and recorded. Next, the same steps were repeated for each concentration of hydrogen peroxide.
Finally, the average of the three tests per hydrogen peroxide solution were recorded on a chart and the work area was cleaned up. Results: The data was collected in this experiment, first, by completing the experimental procedures for the work done with various catalase concentrations and then recording the data and finding the averages. Next, data was collected from the portion of the lab that included work with various hydrogen peroxide concentrations, then it was recorded and averaged.
The averages of both portions of the experiment were then compiled into two other charts and are shown below. The chart and graph in Figure 1 show the relationship between the various catalase concentrations and the time of the reaction, whereas Figure 2 shows the relationship between the time of the reaction and the various substrate concentration. Conclusion: The results for the for the first portion of the experiment testing enzyme concentration show that the hypothesis that the higher the concentration of enzymes the faster the reaction will occur is supported.
The last data point using the 20% enzyme concentration takes much longer to break down the substrate than the other averages, most likely because this set of trials was performed with 3% hydrogen peroxide. The two missing data points in the 80% and 100% enzyme concentration is because the lab was not completed. The experiment results show that an increase in the amount of the enzyme, catalase, will lead to a decrease in the time necessary for the substrate, hydrogen peroxide to be broken down.
The results for the second portion of the experiment testing substrate concentration show that the hypothesis that the higher the amount of substrate the faster the reaction will occur is supported by the data gathered. The experiment results show that the decrease in the amount of time needed for the poison, hydrogen peroxide to be broken down into the molecules oxygen and water is due to the increase in the concentration of substrate.