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Enzyme Lab

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Noah Saunders

on 12 November 2014

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Transcript of Enzyme Lab

Abstract: The object of this lab is to examine the catalase enzyme and test how it reacts to a variety of different tests. These tests include changing the pH, the temperature, the enzyme concentration, and the concentration of the substrate. The entirety of the experiments were conducted within a test tube that was completely submerged into a water bath and a graduated cylinder that was only partially submerged. By measuring the amount of Oxygen within the graduated cylinder over a time period of 5 minutes, the rate at which the enzymes were working can be calculated.
Enzyme Lab

Noah Saunders
Mike Strabone
Eliot Liu
Kyra Sarazen
Aidan Bruton

Part B: The Effect of Enzyme Concentration on Enzyme Activity
To determine the effect of the enzyme concentration on the rate at which the reaction occurs, an experiment was conducted using various concentrations of enzymes. The experiment included enzyme concentrations of 25%, 50%, 75% and 100%, with 100% being the control. These concentrations were obtained by decreasing the amount of catalase used in each trial. The theory behind the experiment indicates that increasing the enzyme concentration directly correlates with the increase in the rate of the reaction. The rates of the reactions are expected to increase with higher concentrations because with more enzymes present, the kinetics of the experiment increases because there are more enzymes present in the same area. More enzymes lead to higher kinetics, which result in the increased likelihood of the enzymes coming in contact with the substrate more frequently, speeding up the reaction.
The data collected supports this theory in how the graphs illustrate that as the enzyme concentration increases, the rates of the reaction also increase. The control of 100% concentration produced the fastest reaction with a slope of .24 mL/sec while the experiment with 25% concentration produced the slowest reaction with a slope of .03 mL/sec. The relationship between the enzyme concentration and the rate of the reaction is directly proportional as depicted on the rate graph in how the data produced a linear function. Such data reinforces the theory that increased enzyme concentration leads to increased reaction rates.
Part E: The Effect of Substrate Concentration on Enzyme Activity
The final experimentation in the lab involved the effect of substrate concentration on enzyme activity. To do this, the experiment was conducted using various concentrations of the substrate, hydrogen peroxide (H2O2). The four concentrations were 0%, 0.3%, 1.5%, and 3.0%. Although the 0% was one of the trials, it was considered to be theoretical. This is due to the idea of enzyme activity in relation to substrate concentration. As substrate concentration increases, the rate of the enzyme increases. This is due to increased collisions with substrate molecules. Therefore, if no substrate is present, it would have a concentration of 0%. This would result in no reaction, because the enzyme would have no substrate to catalyze. The 3.0% concentration of hydrogen peroxide was the control as this was the concentration used in part A. To reduce the concentration of the H2O2, water was added to the 3.0% solution. The 0.3% concentration was prepared by adding 3mL of H2O2 to 7 mL of water, while the 1.5% concentration was prepared by adding 5mL of H2O2to 5mL of water. Once these were prepared, they were tested and the results were graphed.
The data collected supports the theoretical mechanism of increasing substrate concentration. As the concentration of substrate increased, the rate of the reaction increased. If the 0% rate is disregarded, the graph of rate vs. concentration shows that the two are directly proportional. For example, at 0.3% the rate was .1167mLO2/sec. At 1.5% however, it rose to .2167mLO2/sec. Finally, the control (3%) had a rate of .2833mLO2/sec. Therefore, this experiment accurately portrayed the idea that the rate at which enzymes catalyze substrate is directly proportional to substrate concentration.
Although it isn’t specifically shown in what was tested in this lab, this graph wouldn’t continue to increase. Eventually, the rate would not increase anymore, as the maximum rate is achieved. This occurs when the solution is saturated, which occurs when there is such a large amount of substrate that it almost instantaneously collides with an enzyme once that enzyme is finished in breaking down another substrate molecule. When a solution of this nature is saturated, the only way to increase the reaction rate is to add more enzyme.
Part D: The Effect of pH on Enzyme Activity
Part D of the lab involved the effect of pH on enzyme activity. Therefore, the yeast enzyme was used to catalyze the reaction of different pH levels of H2O2 solution. The three pH levels that were tested were 4, 7, and 10. The pH 4 solution was created by adding the 5mL of H2O2 solution to 5 mL of pH 4 buffer (which in turn creates a 1.5% solution of H2O2. The pH 7 solution was the control, as it was created by mixing 5mL of H2O2 solution with 5 mL of water. Lastly, the pH 10 solution was prepared by adding the 5mL of H2O2 solution to 5 mL of pH 10 buffer. In this part of the experiment, the graph of pH of the substrate vs. rate should look like a bell curve. There should be a clear pH at which the enzyme works best (optima), and the rate should be near 0 when the pH diverges too far from it. This is due to the fact that some proteins can’t withstand certain pH levels. Proteins can denature when placed in an unfavorable pH because it can disrupt hydrogen bonds and salt bridges that help the enzyme take shape. Without this unique shape, it is unable to do its job catalyzing the substrate reaction because the substrate would no longer “fit” correctly with the enzyme. Therefore, this part of the lab should reveal catalase’s optima and pH readings where the protein will begin to denature.
The data collected reveals a few things about the catalase. First off, it has a wide range of pH at which it will continue to catalyze the substrate reaction. At both the pH of 4 and 10 the enzyme was still functioning reasonably well. However, the rate does nearly double from pH 4 to 10. At pH 4, the rate of the reaction was .09mLO2/sec. At pH 7, the rate increased and reached .15mLO2/sec. At pH 10 the rate was highest, as it was about .18mLO2/sec. Due to the fact that the rate of the reaction was still increasing when the pH 10 was tested, it is unable to be determined whether or not this was optima for catalase. Therefore, further research was necessary to find out what the optima for catalase is. After researching this, it seems to have an optima of 7.0, although it has a fairly broad range of pH at which it functions best (about 6.8 to 7.5). This data isn’t consistent with the graphs from the experiment. The pH in the experiment showed an increasing rate as the pH rose. However, this is not correct as the rate should’ve been highest at or close to 7.0. This pH error was most likely due to some sort of human error while setting up the experiment.
Part C: The Effect of Temperature on Enzyme Activity
The goal of this part of our experiment was to determine what effect temperature change had on the production of oxygen during an enzymatic reaction. Our first step was to set up our experiment in the same way as our control; however, our variable would lie in the temperature of the tub of water our enzymatic reaction would be taking place in. This temperature in the tub of water varied among 8 degrees Celsius, 23 degrees Celsius, 37 degrees Celsius, and 100 degrees Celsius. For each temperature we measured the enzymatic reaction rate in 30-second intervals for a period of five minutes.

We concluded that our “slowest” rate of reaction was at 100 degrees Celsius as, at this temperature, the enzyme denatured, unfolded. Our second slowest rate of reaction was at 8 degrees Celsius, with 23 degrees Celsius being the second fastest, and 37 degrees being the fastest. The reason why there is an increased rate of oxygen production seen from 8 degrees to 37 degrees is because as temperature increases, collisions are between enzyme and substrate are more frequent, thus more product is being produced. There are lower at 8 degrees Celsius due to fewer collisions between enzyme and substrate occurring, thus less product being produced. One may then question why 100 degrees Celsius does not have a higher rate of reaction than 37 degrees Celsius. The reason for this is that the optimal temperature of the enzyme we used in this experiment, yeast (catalase), has an optimal temperature below 100 degrees Celsius, meaning that at a certain temperature yeast begins to denature due to increasing temperature.

Our control shows that at room temperature, 23 degrees Celsius yeast (catalase) can function properly and sufficiently breakdown substrate, while at 37 degrees Celsius the initial rate of reaction is faster than the reaction at room temperature, but the rate slows down sooner over time. The reason yeast’s optimal temperature is lower than 100 degrees Celsius is due to the environment it normally operates in. Some enzymes have a higher optimal temperature due to their natural environment. This temperature is all based upon where that enzyme will function most productively.
As seen in our graphical analysis, the temperature with the fastest rate of reaction was at 37 degrees Celsius, the second being at 23 degrees Celsius, the third being at 8 degrees Celsius, and the fourth being at 100 degrees Celsius. Refer back to the section on the theory behind this for an in-depth explanation of this trend.
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