Factors Affecting the Rate of Enzyme Activity

The Purpose of doing this experiment is “how factors affect on the rate of enzyme activity.” “We examine the affects of enzyme activity when exposing enzymes to different substrates, PH and temperature. In this experiment a type of enzyme called Peroxides has been used. Peroxidase is the enzymes are found in living organism so, it can be founded in both liver and potato. For measuring the rate of enzyme activity in each experiment the height of the frothy foam column formed by the reaction’s product have been measured by mm, within a 60 seconds.

Then the units changed to mm/h. Rate is distance over time and it means how fast something occurs in a given time period. The enzyme peroxidase in two forms of potato peroxidase and liver peroxidase has been settled in two different situations, (different PHs: 3,7,11), (different temperature: cold, warm and hot) and in other experiment mixes with three different substrates: (water, H2O2, glucose solution). The data collected during the experiment make discussion about hypothesizes.

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The confirmation of the substrate for peroxides hypothesis: Hydrogen peroxide would be the best substrate for peroxidase and the reaction between liver peroxidase and hydrogen peroxide will be stronger than potato peroxidase and hydrogen peroxide. Peroxidase facilitates the “breakdown of their substrate metabolically produce toxic hydrogen peroxide.” The reaction is: 2H2O2 & enzyme  2H20+O2 & enzyme. H2O2 works as substrate. H2O2 is strong oxidizer. That it is considered a highly reactive oxygen spices. Also, the available peroxidase in potato and liver has the same function as with oxidase.

Regarding to the function of liver, which is filtering, there should be lots of oxygen radicals in liver. A Potato is a storage tissue comparing to the liver has less free oxygen radicals so the reaction of potato peroxidase with H2O2 is slower than the liver peroxidase.

In other point of view, among proposal substrates in this experiment such as water, glucose solution and H2O2, hydrogen peroxide increases the concentration of O2 and H2O (result of transforming of hydrogen peroxide) when it places next to peroxidase liver rather than when it places next to peroxidase potato. Therefore, when concentration increases, the intensity of reaction increase. The data also showed the same results. Adding 3ml of H2O2 to the potato peroxide gave 41 mm of foam height and the enzyme rate was 2460 mm/h. Adding 3ml of H2O2 to liver peroxidase gave 151 mm foam height and 9060 mm/h as enzyme rate. When water and glucose solution added to peroxidase in liver and potato, any reaction happened so, no bubbles created. The hypothesis has been approved in first experiment. *

The effect of temperature on peroxidase activity hypothesis: As the temperature increases, the enzyme activities will increase until it reaches the optimum temperature range, and after that the enzyme activities will decrease. Meanwhile, liver peroxidase activity due to increasing temperature should be more than potato peroxidase activity. Increasing temperature at the beginning, cause the enzyme activity increases because there is more energy to speed up the reaction. Then, the enzyme activities start to decrease because the changes to active site due to the temperature will no longer fit substrate. The data collected during the experiment showed more activity in potato peroxidase at 5 C as cold temperature rather than 35 C as warm temperature and it did not have any reaction when the enzyme placed in hot temperature 68 C. with increasing temperature the potato peroxidase lost its activity.

The first part of the hypothesis failed because based on the hypothesis it supposed to be seen more activity in potato enzyme at 35 C rather than 5 C, but it did not happen. It can be guessed that Potato lives under the ground where there is not enough sunlight and as a result it is colder than surface of the ground and potato enzymes are active in low temperature and it will lose its activity when the temperature be higher. But, the experiment about the liver peroxidase approved the hypothesis. Liver had wow reaction at 6 C as cold temp and at 33 C as warm temp too. And it had no activity at 64 C at all. As it is an enzyme found in the body, the optimum temperature would usually be body temperature around 37 C then, high activity of liver peroxidase at 33 C is expectable. But, high activity at 6 C is unusual.

Maybe an error occurred during the experiment such as not reading the temperature correctly or the room temperature (which is optimal) effects on the reaction during the experiment or maybe the time reader made mistake in setting time. However, the 64 C is absolutely not optimal because the structure of enzyme and its active site has been destroyed in high temperature. Regarding to the second part of the hypothesis, 9060 mm/H rate of enzyme activity in liver peroxidase at 6 and 33 degree of Celsius showed more activity in compare to 2100 mm/H and 1980 mm/H of potato peroxidase at 5 and 35 degree of Celsius. So second part of hypothesis has been approved.

The effect of PH on peroxidase activity hypothesis:

Increasing pH causes increasing the activity of the enzyme until it reaches optimum pH range and after this it will decrease. About potato peroxidase as the pH increases, the activity of the enzyme will increase until it reaches optimum pH range, which could be around pH 7, because the enzyme is less denatured when it reaches the preferred pH level, and after this it will decrease because the active site will change in shape and it will no longer accept substrates. The experiment showed 2400 mm/H rate of activity for potato peroxidase in PH 7 and 2220 mm/H rate of activity in PH 3 and 2040 mm/H rate of activity in PH 11. The result absolutely confirmed the hypothesis. PH7>PH3>PH11 About liver peroxidase, increasing PH cause increasing enzyme activity until it reaches optimum pH range but as liver use to live in a buffer situation the differences in activities due to changes in PH cannot be much a lot. It does not mean that it is able to work in any PH situation.

Liver also has an optimal range and does not work out of that range. In this experiment the expectation was high activity around PH 7, which is close to the PH of body, 7.5, But 882 mm/H rate of activity in PH11 was the most active situation. Also 842 mm/H in PH7 was more than 828 mm/H in PH3. Then liver peroxidase activity increased by increasing PH level and it means that Hypothesis has been failed. PH11>PH7>PH3 Regarding to the data collected by the class some of the hypotheses have been approved and the others have been failed. Data table for confirmation of substrate for peroxidase showed that in both cases, potato and liver, H2O2 was the best substrate among water and glucose and hydrogen peroxide. Also the enzyme activity of liver (9019 mm/H) was more than enzyme activity of potato (2245 mm/H). The difference was so obvious in the graph.

So, the hypothesis about substrate approved. The data collected by the class about how temperature effect on enzyme activity of potato and the graph showed that enzyme activity decreased by increasing the temperature. Therefore, the hypothesis is not true about potato enzyme. But, the data of the class supported the hypothesis about the liver peroxidase. The graph also showed how increasing temperature effects on liver enzymes. The liver enzymes got more activity in warm temperature comparing to the cold temperature and it was absolutely inactive in hot temperature. The data collected by the class about how PH effect on potato peroxidase showed that in PH7 enzyme activity of the potato is still the highest level of activity but the data showed more activity in PH11 than PH3. Although this part is different of what did our group get in this experiment but the hypothesis is still true. As graph showed, 8645 mm/H in PH11 and 7525 mm/H in PH7 and 6640 mm/H in PH3, the enzyme activity in liver increased when level of PH increased and it was also against of the hypothesis in this experiment just like what did our group go. Many errors may have been occurred in this experiment.

The situation and condition were not the same for all groups. For example there were no specific definition for the words “ cold, warm or hot”. Any group may measured the height of the bubbles in any temperature as cold or warm or hot. There may even be errors in inserting the data in the table online. Because some of the data is totally out of range and out of suggestion. However, PH, temperature and even the substrate effect on enzymes activity. An enzyme has special active site and special substrate can be attached to it. The optimal range is important in enzyme activity. The enzyme is less active when it gets under or above the level of optimal range. And it is true about both PH and temperature.

In our real life we come across with many situations that can effect on the enzymes whether inside or out of our body. For example in the human digestive tract, there are enzymes operating at basic pH (mouth and intestine) and highly acidic pH (stomach). If the acidity of the stomach highly increases the enzymes are not able to work any more. Or, some people have some problem to digest dairy because of enzyme deficiency. Or, if a child has fever the enzymes of his/her body won’t be able to work any more and it causes vomiting.