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Unformatted text preview: Introduction Every time apples are cut into slices for picnic lunches, the apples are brownish colored by the time the meal arrives. This is due to the oxidation of catechol which turns into benzoquinone and water. Catecholase, which is naturally found in apples, is the enzyme which catalyzes the reaction. Catecholase is found in many plants and is a component of the repairing system. When the inside of the apple, in this case, is exposed to oxygen, the catechol is oxidized. Benzoquinone is produced and acts as an antiseptic for the apple. The reaction is as follows: Catechol + O 2 (in the presence of catecholase) Benzoquinone + H 2 O The Enzyme catecholase speeds up the reaction by lowering the activation energy required for the reaction to occur, but none of the enzyme is used up in the reaction (DeSaix). The oxidation of catechol into benzoquinone was observed in an experiment. The experiment tested whether or not catecholase would catalyze the reaction of catechol and oxygen to form the product benzoquine and also tested whether the enzyme solution used would form any benzoquinone without the presence of added catechol. To conduct this experiment, a spectrophotometer was used for the absorbance of solutions in three test curvettes. Four test curvettes were prepared, one containing only catechol and water, one containing only the enzyme solution and water, one containing catechol, water, and the enzyme solution, and one that served as the calibration tube. After calibrating the spectrophotometer absorbance, readings were gathered initially and then after the curvettes sat in a 37 o C water bath. The readings showed that the curvette with only the enzyme solution and water formed very small amounts of benzoguinone because of small amounts of catechol being in the enzyme solution, and that the curvette with only catechol produced nearly zero benzoquinone. But, primarily, the readings showed that the curvette with catechol in the presence of the enzyme did in fact produce benzoquinone. This result allows for the assumption that in the following experiments, catecholase will act as an enzyme in the catechol + oxygen benzoquinone + H 2 O reaction. After an apple is cut or bitten into, if it is put in a cool climate (such as a refridgerator), it will turn less brown than an apples left in a warm climate (such as the sun). From this observation it is plausible to say that the production of benzoquinone is increased as temperature is increased. The first experiment in this lab tests the effect different temperatures have on the production of benzoquinone. The production of benzoquinone is measured after the reaction has occurred in four different environments; one at 0 o C, one at 37 o C, one at room temperature, and one at 60 o C. The temperature of the different environments is the independent variable and the amount of benzoquinone produced is the dependent variable. From the observation of the apple turning brown when exposed to sunlight (added head), I expect that as the temperature of the...
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- Spring '08