Rate of Activity of the Enzyme Catalase in Hydrogen Peroxide Experiment

In this study of increasing target temperature of enzyme catalase coated onto paper filter disks reacting through 3% hydrogen peroxide solution in culture tubes, there was an increase in amount of time taken for the enzyme catalase coated filter paper disks to float to the top of the 3% hydrogen peroxide solution in culture tubes (table 2) as the temperature of the catalase enzyme passed the 40 mark. All of the paper filter disks coated with enzyme catalase were placed in the same amount and temperature (in mL and filled to the same level in every culture tube with 2cm gap from top of culture tube) of 3% Hydrogen peroxide solution in culture tubes. All the filter paper disks coated with enzyme catalase were damp, opaque, white and solid (table 1) before exposure to 3% hydrogen peroxide solution and after exposure to 3% hydrogen peroxide they were fuzzy with bubbles on them, solid, damp and white (table 1). The fuzziness and bubbles indicate the reaction of the enzyme catalase coated onto the filter paper disk occurred with the 3% hydrogen peroxide in the culture tube and that oxygen was produced, which were the bubbles as it should according to the literature decomposition balanced equation of 3% hydrogen peroxide where enzyme catalase is the catalyst.

The 3% hydrogen peroxide was clear, colourless and liquid before and after the reaction with the filter paper disk coated with enzyme catalase (table 2) in the culture tubes. The observations and analysis (table 2 & 3 and figure 1) support the hypothesis of the relative reaction rate of catalase enzyme increasing up to a certain temperature (around 37C for humans) then decrease past the optimal temperature (around 37C in humans) because the enzyme begins to denature. Firstly, from temperatures 0-40C (table 2) of the enzyme catalase coated onto filter paper disk there was a small increase in time taken (about 0.2-0.5 for each trial) to rise the top of the 3% hydrogen peroxide solution in the culture tube and then a huge increase in time (about 10 seconds increase for each trial) from 40-60C (table 2) of the enzyme catalase coated onto filter paper disk. Then from 60-80C temperature of the enzyme catalase coated onto filter paper disk it was an almost infinite time increase (from about 15 seconds to no reaction which could be almost infinite) as no reaction was occurring in the 80C temperature condition (table 2).

Additionally there is a huge increase from 0C to 60C and 80C (from about 3.5 seconds of 0C to about 15 seconds for 60C and to almost infinite for 80C). Secondly, Table 3 shows that the that the relative enzyme catalase reaction rate increases from 0.227/s to 0.292/s for temperature 0C and 20C respectively. This shows that the relative reaction rate for the enzyme catalase is increasing as it’s getting closer to its’ optimal temperature (around 37C in humans) which is where the enzyme functions most efficiently. For temperature of 40C the relative reaction rate of catalase enzyme is beginning to decrease (goes from 0.292/s of 20C to 0.236/s for 40C temperature). This suggests that the highest relative reaction rate for enzyme catalase is in between 20C to somewhere before 40C (around the literature value of 37C) as the relative reaction rate begins to drop at 40C. For temperatures past 40C which are 60C and 80C the relative reaction rate of enzyme catalase decreases incredibly (0.077/s and 0/s respectively).

Thirdly, Figure 1 Illustrates that as the temperature is increased the mean relative reaction rate of enzyme catalase increases up to about 37-39C (up to around 0.3/s mean relative reaction rate). Then past the 37-39C mark, the mean relative reaction rate of enzyme catalase begins to drop from 40C and onwards. The mean relative reaction rate is about 0.24/s for 40C and about 0.08/s for 60C, both of which are smaller than the mean relative reaction rates of 0C and 20C (0.28/s and 0.29/s respectively).When it reaches 80C there is no reaction occurring meaning a mean relative reaction rate of 0/s. Additionally, the error bars (based on the standard deviation) only overlap for temperatures 0C, 20C and 40C which are below/near (respectively) to the optimal temperature of enzyme catalase, which suggests that the mean relative reaction rates of those temperature condition do fall within the same range. The error bars however do not overlap at temperatures 60C and 80C with each other and with any other temperature condition (0C, 20C and 40C), which suggests that the mean relative reaction of 60C and 80C do no fall within the same range of each other’s mean relative reaction rates and any other conditions mean relative reaction rate.

Finally, according to the t-tests shown in table 4, the t-values (6.21, 5.51, 10.4, 14.8 and 8.55) are much greater than the critical values (2.308 for all comparisons at p=0.05) for every comparison except for the 0C to 20C, 20C to 40C and 0C to 40C comparisons where the t-values are below (0.501, 2.08 and 1.48 respectively) the critical values (2.308, 2.308 and 2.308 respectively at p=0.05). This indicates that the null hypotheses (except for the 0C to 20C, 20C to 40C and 0C to 40C comparisons) are incorrect meaning the differences in the mean relative reaction rates of enzyme catalase are significant. These significant differences further support the hypothesis as it illustrates that temperatures above the optimal (37C) by a huge amount (ex. Temperatures that are greater than 40C) incredibly lower and/or even completely stop enzyme reaction rate activity due to denaturation of high temperatures. These t-tests show that any differences between the means have a less than 5% chance of simply being due to random variation. For the t-test values (0.501, 2.08 and 1.48) below the critical values (2.308 for all comparisons at p=0.05), the difference in mean relative reaction rates are not significant which supports the null hypotheses. These non-significant differences further support the hypothesis as it illustrates that temperatures around and below (down to 0C) the optimal 37C (in humans) have a high enzyme reaction rate. These t-tests show that any differences between the means have a greater than 5% chance of simply being due to random variation.

The observations and calculated values support the hypothesis, illustrating that the relative reaction rate of enzyme catalase increases until it reaches an optimal temperature of approximately 35-40C which is close to the human body temperature (Campbell and Reece, 2002). Any temperature above the optimal temperature of enzymes causes denaturation to occur to the enzyme due to the increase in the motion of molecules which increases heat that causes breakage of bonds (which maintain the structure of the enzyme) in the enzyme. (Allott, 2007) The denaturation thus causes a decrease in the mean relative reaction rate of catalase enzyme because the substrate (in this investigation is hydrogen peroxide) does not fit the active site of the enzyme (in this investigation is catalase enzyme). The huge difference in mean relative reaction rate of catalase enzyme between 0C to 80C explains the denaturation of the catalase at high temperatures. And the little variation of the mean relative reaction rate at the lower temperatures of catalase enzyme of 20C and 40C support the hypothesis as they are close to the 35-40C optimal temperature. Overall the data and values support the hypothesis.

Evaluation:

The filter paper disks were drying up quickly after being patted with a paper towel to remove excess liquid. The dried filter paper disks become less sticky and fall off the rubber stopper (when trying to insert them into culture tubes) into the 3% hydrogen peroxide solution before the culture tube was inverted. This caused the production of oxygen (bubbles) to happen sooner and since both sides of the filter paper disks are reacting in the beginning (as compared to only one side reacting at the beginning until it somewhat rises into the 3% hydrogen peroxide solution) it resulted in a decrease in amount of time taken to rise to them top of 3% hydrogen peroxide solution which increases relative reaction rate of the enzyme catalase. To fix this, dip only one paper filter paper disk into catalase enzyme solution at a time, and tap each side carefully using tweezers on paper towel and immediately place onto rubber stopper so they are still sticky.

The enzyme catalase extract solution was obtained from a beaker. For the temperatures of 40C, 60C and 80C the beakers were placed on hot plates to keep the temperature consistent. Since the beakers were left on the hot plates for a while, at high temperatures especially the 80C condition, the water in the solution of the enzyme catalase can begin to evaporate and thus increasing the enzyme concentration in the solution. This causes the relative rate of enzyme activity of catalase to increase (meaning takes less time to flout to top of 3% hydrogen peroxide solution) as there are more enzymes to decompose hydrogen peroxide for the 40C, 60C and 80C temperature conditions. To fix this problem, heat up the catalase enzyme extract solution to the desired temperature condition and use that catalase enzyme extract solution immediately to minimize evaporating of water.

References:

Campbell N, Reece J. 2002. Biology. San Francisco: Pearson/Benjamin Cummings. Pg.100.

Allott A. 2007. Biology. Oxford: Oxford University Press. p19.