Investigating the Enzymatic Activity of Catecholase through Temperature, pH, Enzyme Concentration, and Substrate Concentration
University of Alabama at Birmingham
Enzymes are macromolecules that act as catalysts in living organisms by speeding up chemical reactions without being changed or destroyed by the reaction (Campbell and Reece, 2008). Enzymes are able to speed up the rate of a chemical reaction by decreasing the activation energy during the reaction (Garcia-Viloca et al., 2004). Activation energy is the lowest amount of energy needed to begin a chemical reaction (Campbell and Reece, 2008). Few biochemical reactions could take place quickly enough to satisfy the metabolic needs for living organisms without the aid of enzymes (Helms et al., 1998). Biological enzymes used in cells are seen in the form of proteins. These catalysts have complex structures including one or more polypeptide chains which are folded in specific shapes to contain an active site, which is the area a substrate will bind to the enzyme. A substrate is a molecule which the enzyme will act upon and change (Helms et al., 1998).The substrate which is bonded to its specific enzyme is known as an enzyme-substrate complex, and the results of the catalytic action between the enzyme and substrate change the substrate to the product(s) of the reaction (Campbell and Reece, 2008). The active site of an enzyme is specific for the substrate. According to Cambell and Reece, when the substrate enters the active site the shape of the enzyme will change very minutely to better fit the substrate in the active site. The very tight fit between the substrate and the active site is called an induced fit (Campbell and Reece, 2008). This induced fit or conformational change is another reason why the activation energy is lowered during the chemical reaction (Garcia-Viloca et al., 2004). The enzyme that is being tested throughout this experiment is the enzyme catecholase. According to Helms et al., catecholase is found in a few fruits and vegetables and is responsible for the inside of the fruit or vegetable turning brown when exposed to air. The brown color is a result of the catechol oxidation and conversion to benzoquinone. The benzoquinone forms chains that are the structural centerpieces of the brown and red pigments that cause the fruit to darken. The activity of catecholase is based on some environmental factors (Helms et al., 1998). The purpose of this experiment is to test some of these environmental factors such as temperature, pH, enzyme concentration, and substrate concentration in order to find out what effects each have on the efficiency and productivity of the enzyme. Hypotheses
The null hypothesis is that the temperature of the system will have no effect on the enzymatic activity. The alternative hypothesis is that an increase in the temperature of the system will increase the amount of enzymatic activity. pH
The null hypothesis is the pH of solution will have no effect on the enzymatic activity. The alternative hypothesis is the enzyme used will have an ideal pH. A solution with too high or too low pH will cause a decrease in the amount of enzymatic activity observed. Enzyme Concentration
The null hypothesis is enzyme concentration will have no effect on the enzymatic activity. The alternative hypothesis is an increase in enzyme concentration will increase the enzymatic activity. The converse will also be true. Substrate Concentration
The null hypothesis is the substrate concentration will have no effect on the enzymatic activity. The alternative hypothesis is an increase in substrate concentration will increase the amount of enzymatic activity. Materials and Methods:
To test the effect of temperature, three test tubes were labeled 10, 24, 50, and filled with 3 mL of a phosphate buffer of pH 7. One test tube was placed in an ice bath, one was left at room...
References: Campbell, Neil., Jane Reece. 2008, Biology, 8th ed. Beth Wilbur ed. Benjamin Cummings
Publishing, San Francisco, California. pp. 152-155.
Garcia-Viloca, Mireia., Jiali Gao., Martin Karplus., Donald G. Truhlar. "How Enzymes Work:
Analysis by Modern Rate Theory andComputer Simulations." Science 303.5655
(2004):pp. 186-195. Academic Search Elite. EBSCO. Web. 4 Mar. 2010.
Helms, Doris., Carl Helms., Robert Kosinski., John Cummings. 1998. Biology in the Laboratory,
3rd ed. Judith Wilson ed. Freeman Publishing, New York, New York. pp. 10-1-10-14.
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