Autor: wong 25 April 2010
Words: 976 | Pages: 4
Effects of Temperature and pH on Catalase Activity
Enzymes are organic catalysts that spur metabolic reactions. The presence of an enzyme within a cell is essential in order for any sort of reaction to take place. All enzymes are complex proteins that act in an organismâ€™s closely controlled internal environment. In such a homeostatic environment, the temperature and the pH (concentration of hydrogen ions), remain within a fairly narrow range. Extreme variations in pH and temperature denature the enzyme by altering its chemical structure, thus adversely affecting the chemical reaction. As even the slightest change in the proteinâ€™s structure will change the enzymeâ€™s shape enough to prevent the formation of the enzyme-substrate complex, the reaction will then be unable to take place. The enzyme, catalase, reacts with hydrogen peroxide in order to yield water and oxygen. Therefore, upon reaction, bubbling will occur as oxygen is produced. The amount of bubbling, or oxygen that is produced is dependent on the conditions under which the reaction takes place (or fails to).
The Purpose of this experiment was to determine the optimal temperature and pH levels under which enzymatic reactions involving the enzyme catalase and the reactant, hydrogen peroxide, may successfully occur.
It is hypothesized that because extreme variations in temperature and pH will negatively affect the reaction, mild temperatures and more neutral ph levels will yield the best results (most bubbles).
In order to conduct the tests on temperature and pH, 8 test tubes were used; five for temperature, and three for pH. Upon preparation for the tests, the three temperature test tubes were marked at the 1 cm and 5 cm levels, while the three pH test tubes were marked at the 1, 3, and 7 cm levels. To test for temperature, each tube was placed in a separate location with varying temperature: a refrigerator (5 degrees), an incubator (32 degrees), Boiling water (99 degrees),a warm bath (22 degrees), and a hot bath (85 degrees). After placing each tube in its experimental setting, 15 minutes elapsed before removing them. Immediately after removing the tubes, hydrogen peroxide was added to each tube up to the second (5 cm) mark. They were then swirled to mix, and after fifteen seconds, the bubble columns in each vile were measured in millimeters, and then recorded in a data table. The procedure for analyzing pH levels was rather different. The three test tubes, marked at three different levels, were each filled to the first mark (1cm) with catalase, and to the second mark (3 cm) with water. However, the pH of the water had been adjusted differently for each vile. The first tube received water adjusted to pH three, the second received water adjusted to pH seven, and third received pH eleven. Consequently, each tube was then filled to the last mark (7 cm) with hydrogen peroxide, swirled to mix and then observed after twenty seconds. After twenty seconds passed, the bubble columns of each of he tubes were measured in millimeters. Results were recorded on a chart.
As expected, during the temperature test, the least amount of bubbles were emitted in tubes that had been exposed to extreme heat. The tube placed in boiling water yielded zero millimeters of bubbles. The boiling water denatured the enzyme and altered its chemical structure rendering it incapable of undergoing metabolic reactions. For these same reasons, the vile placed in a hot bath, containing water at 85 degrees, produced only one millimeter of bubbles. There seems to be a strong correlation between hot or warm temperatures and decreased levels of oxygen production, as the test tube placed in an incubator yielded only sixteen millimeters of bubbles. However, colder temperatures seem to facilitate the enzymatic reaction as test tubes placed in such gave off ample amounts of oxygen (bubbles). For instance, the catalase which had been in the refrigerator produced a bubble column of twenty five millimeters, and the test tube yielding the largest bubble column of thirty-eight millimeters had been partially immersed in an ice cold bath of twenty- two degrees. (See Graph 1.1)
During the test for pH, when hydrogen peroxide was added to the catalase/water solution with a pH of 3, which is acidic, thirty four millimeters of bubbles were produced. After adding hydrogen peroxide to a basic solution, with the pH of 11, the bubble column reached only fourteen millimeters. The enzyme, catalase, appears to react best when in a solution with a basic pH, based on the formation of a thirty-seven millimeter bubble column when a catalase/water solution, with pH of 7, was combined with hydrogen peroxide. ( See graph 1.2)
Every reaction requires its own specialized enzyme, which is uniquely capable of functioning under the conditions in which the organism exists, to create metabolic reactions within its cells. The enzyme, catalase, is derived from potatoes and is present in cells where it speeds up the breakdown of hydrogen peroxide to water and oxygen. Potatoes are grown under ground in rather cold conditions, and in soil with rather basic acidity. Therefore, it is feasible to hypothesize that a potatoâ€™s metabolic catalyst would perform best under conditions that are similar to those under which potatoes grow. Such a theory is clearly supported by the results of the experiment, which indicate that the largest amount of bubbles (38mm) in the temperature test occurred at the coldest temperature of twenty two degrees, and the largest amount (37 mm) occurred in a basic water/catalase solution (pH7). The results of the experiment also bolstered the scientific concept that certain enzymes work best under specific, narrowly varying conditions within a homeostatic organism. Extreme variations in temperature and pH in the experiment produced lagging results, suggesting that the enzyme structure had, in deed, been altered in such a way that was detrimental to the reaction.