Part 3:
- Repeat Part 2 and change the temperature range to 30˚C - 35˚C.
Part 4:
- Repeat Part 2 and change the temperature range to 35˚C - 40˚C.
Part 5:
1. Repeat Part 2 and change the temperature range to 40˚C - 45˚C.
Part 6:
1. Repeat Part 2 and change the temperature range to 45˚C - 50˚C.
Part 7:
1. Repeat Part 2 and change the temperature range to 50˚C - 55˚C.
Part 8:
- Repeat Part 2 and change the temperature range to 55˚C - 60˚C.
Part 9:
- Fill up a second beaker with ice cubes.
- Using a tong, soak a felt disk in the yeast solution for 3 seconds.
- While one person is in control of the felt, another lab partner must submerge one test tube into the beaker with ice and put the temperature probe in the test tube.
- At the same time, a third lab partner must begin the LoggerPro program on the laptop by clicking COLLECT in order for the temperature probe to take temperature readings. In this trial, the temperature readings should be in the 10˚C - 15˚C range.
- Repeat steps 4-6 from Part 1. To adjust the temperature of the hydrogen peroxide, add or remove ice in the beaker to reach the desired temperature.
- Repeat steps 2-5 from Part 9 four more times and use a different unused test tube each time.
Part 10:
- Repeat Part 9 and change the temperature range to 15˚C - 20˚C.
Observations:
Interpretations:
When H2O2 is in the presence of an enzyme called yeast, it breaks down according to the following formula: 2H2O2 → 2H2O + O2.
The enzymes break the compound down into water and gaseous oxygen. When the piece of felt is dropped into the test tube, it sinks to the bottom. And when the yeast begins to react with H2O2, the gaseous product rises and pushes the felt to the surface. The amount of time it takes for the felt to complete its travels represents how fast the gaseous products are being formed. So, it shows how fast the reaction occurs.
Temperature makes a difference in the speed of the reaction because it controls the speed at which all the molecules travel. By increasing the temperature, the speed of the molecules increases. Therefore, their chances of collision increase as well. So, by raising the temperature of H2O2, they become more likely to collide into the active site of a yeast enzyme and react. Also as the temperature increases, there is more free energy in the system. Thermal energy absorbed into the reactants decreases their stability as molecules because they become more agitated. That makes them more likely to break their bonds. So, the activation energy for the reaction is reduced and the job of the enzymes becomes slightly easier. The opposite is true too. If the temperature decreases, the reaction process decreases as well because molecules move much more slowly and remain more stable.
Temperature also affects the activity of an enzyme. Increasing temperature increases the reaction process, but after a certain temperature (the optimum temperature), the speed of the reaction drops sharply. The high temperatures disrupt the hydrogen bonds, ionic bonds, and other weak interactions in the enzyme and cause it to lose its shape. This means that the enzyme has denatured and can no longer function as a catalyst. The optimum temperature is the temperature at which the collisions of the substrate and the active site of the enzyme are the highest without the enzyme denaturing.
The graph of Temperature of H2O2 vs. Time of Felt Travel represents the reaction progress and enzyme activity controlled by various temperature ranges and proves the explanation of temperature effects on enzyme activity to be true. The graph shows a gradual decrease in travel time as the temperature increases. Therefore, it is true that the reaction progress increases from faster moving and less stable molecules.
The temperature ranges with the lowest time of felt travel were the 40˚C - 45˚C range and the 50˚C - 55˚C range. Thus, according to the graph, both those ranges would be the optimum temperatures for enzyme activity. However, in reality that is not possible because after the optimum temperature has passed for an enzyme, it should begin to denature. So, one of those results are false due to experimental error. In order to determine the correct optimum temperature range, the 45˚C - 50˚C range and the 55˚C - 60˚C range show a gradual increase in the time of felt travel if the 50˚C - 55˚C range is ignored. Therefore, it is more likely that the 40˚C - 45˚C range is the optimum temperature range for the enzyme. Also, the trials recorded above that range were tested on a different day where a higher yeast concentration was possibly used. This would affect the reaction rate in comparison to the first day. If, for example, the enzymes were saturated on the first day, and a higher concentration of it was used on the second day, there would be greater productivity and the reaction would speed up. That was probably true because of the time resulted in the 50˚C - 55˚C range was lower.
After the optimum temperature range, the time began to increase as demonstrated by the graph. This is because when the temperatures become too high for the enzyme, some of its bonds get disrupted and cause the enzymes to denature a bit. Eventually, the temperatures will become high enough to denature the enzyme completely which means that the felt would never come back up because the enzyme has completely lost its form. Besides denaturing enzymes, high temperatures will disrupt the weak interactions such as hydrogen and ionic bonds that hold the enzymes to the substrates. So, very high temperatures can destroy the entire system.
In the temperature ranges under 20˚C, the time of the felt travel is evidently much longer than all the other temperature ranges. These results prove that slower moving particles have a big impact on the overall reaction since the frequency of substrates and enzymes colliding are drastically decreased. Also, the molecules in solution begin to freeze to the shape that they’re in because the bonds in their bodies are held still. This affected the overall reaction because the enzymes weren’t able to change their shape to make an induced fit in order for the substrates to bind to the active sites properly. As a result, the enzymes weren’t as capable to carry out the reaction. So the graph proves to be a decently accurate representation of the effects of enzyme activity as a result of changing temperatures.
Sources of Error:
There are several sources of error in this lab. Since the lab takes a very long time to complete, the experiment had to be continued over several days. As a result, different H2O2 and yeast solutions were used on each day. Some of the solutions may have been older than the original solutions used which may have had an effect on their reactivity. Also, different concentrations of solutions may have been used. For example, when the original yeast solution ran out, a new solution had to be made and probably resulted in a slightly different concentration.
When filling the test tubes with H2O2 and tap water, the water was filled up to the ¾ mark instead of a specific measured volume of water. As a result, different amount of water in the solution change the concentration of H2O2. And, the ¾ marks weren’t all exactly at the same spot on each test tube. An additional source of error is that the H2O2 wasn’t mixed into the water properly since it was not stirred with a stirring rod. So, some areas of the solution may have been of a higher H2O2 concentration than others.
Another source of error is the amount of time the felt was soaked in the yeast solution. It is difficult to keep it in there for exactly 3 seconds each time, so some felts may have had more yeast enzymes than other felts. Also, the size of each felt may have differed to a certain limit and each felt would have a different surface area to hold the enzymes.
Time was also a big factor. The time when the felt was dropped into the test tube wasn’t always at the exact same time when the stopwatch was started. The same goes for when the stopwatch was stopped. And, when the test tube was taken out of the beaker for the felt to be dropped in, the temperature of the solution dropped since it was no longer heated.
The final source of error was when the felt rose to the surface of the solution. As it began to rise, it sometimes rubbed against the glass. This caused friction and the felt would drop its speed in its travel to the top. Other times, the felt would rise in a vertical position rather than horizontal. This increased its speed as it became capable to cut through the solution above it rather than push it out of the way as it rose to the top.
Due to all of these sources of error, we decided to record the trials in temperature ranges instead of specific temperatures because the results were different each time. That’s why it was useful to repeat each trial several times and take the averages of the results rather than base our experiment on the results of specific temperatures.
Conclusion:
The graphical results found represent the relationship between the progression of the reaction and temperature. Increasing the temperature caused more frequent collisions between the enzyme and its substrate. Decreasing the temperature to under 20˚C with ice decreased collisions amongst the molecules and consequently drastically decreased the reaction progress. The optimum temperature found was in the 40˚C - 45˚C range where the reaction progress was the highest. After that temperature, the reaction process decreased as the enzyme began to denature. The results in the 50˚C - 55˚C range were affected by experimental error, so it is not the optimum temperature range for the yeast enzyme.
