BY 123 Lab Report Rough Draft - The Effects of Varied...

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The Effects of Varied Temperatures, pH Values, Enzyme Concentrations, and Substrate Concentrations on the Enzymatic Activity of Catecholase By: Roshni Sheth February 25, 2010 BY 123L: Section P9
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Introduction: Enzymes are biological catalysts that are able to speed up a reaction by lowering the activation energy of that reaction, or the amount of energy needed to start a reaction so the bonds of the reactants can break (Campbell and Reece, 2008). In order for living systems to survive, enzymes must be present to speed up metabolic reactions because the reactions do not occur rapidly enough naturally (Whitford, 2005). Most enzymes are proteins, making them macromolecules. Proteins are polymers that are made up of amino acids, each one containing an amine group and a carboxyl group (Campbell and Reece, 2008). A unique fact about enzymes is that they are not changed or expended by chemical reactions, but rather, they can be reused after the reactions has been completed (Helms, et al, 1998). The enzyme catecholase, also known as catechol oxidase, is an oxidoreducatse that works on phenols, which means it catalyzes the oxidation of phenols(“EC - Catechol oxidase,” 1978). Cofactors are needed to catalyze reactions more effectively (Whitford, 2005). The cofactor of this enzyme is copper. The chemical equation of its reaction: 2 catechol + O 2 → 2 benzoquinone + H 2 O (“EC - Catechol oxidase,” 1978). Potatoes and some fruits become brown when they react with the air because they contain catecholase, which makes the aforementioned reaction go. Catechol makes the product benzoquinone, which links to form long, branched chains that make up the melanoid pigments that make the potato or fruit become darker (Helms, et al, 1998). Certain factors, such as changes in temperature, pH levels, enzyme concentration, and substrate concentrations, can affect the enzymatic activity. As the temperature increases, the enzymatic activity increases, due to there being more collisions between enzymatic molecules and the substrate molecules, until the temperature goes above the optimum temperature. For most enzymes, temperature about 40°C will make the enzyme denature, which means that the secondary or tertiary protein structures of the enzyme are destroyed. Similarly, as the pH value increases, the amount of enzymatic activity increases until the pH passes the optimum pH value for the enzyme. Then, the enzymatic activity begins to decrease. Any pH values that are higher or lower than the optimum pH value will produce low rates of enzymatic activity because of denaturation. As enzyme concentration increases, the rate of enzymatic activity will increase proportionately only if there is an excess amount of substrate present in the solution. If the amount of substrate is not in excess, then the substrate will act as a limiting reagent in the reaction. This proves that the substrate concentration is also a factor. If the enzyme concentration is constant, and the amount of substrate is increased, the rate of enzymatic activity will increased
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BY 123 Lab Report Rough Draft - The Effects of Varied...

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