The Effect Of Alkaline Ph On Reaction Rate Of The

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The Effect of Alkaline pH on Reaction Rate of the Enzyme Catecholase Introduction Enzymes are essential to the metabolism of biological organisms. Several factors can influence the reaction rate of enzymes: temperature, pH, enzyme concentration and substrate concentration (Ainsley, 2010). Catecholase, an enzyme in the tyrosinase/polyphenol oxidase family, is responsible for the browning seen in potatoes, apples and mushrooms after they are cut (Capworth, 1998). These fruits and vegetables contain small amounts of catechol, along with the enzyme catecholase, that reacts with oxygen in the atmosphere and forms the brown compound benzoquinone (Hemelstine, 2004). This reaction can be delayed or prevented in fruits and vegetables by the addition of acids, such as lemon juice, and by cooking (Hemelstine, 2004). In this experiment, the effect of pH on the rate of reaction of the enzyme catecholase will be examined. Since it has been found previously that acid can inhibit this enzyme (Hemelstine, 2004), this study will examine the effects of alkaline pH on enzyme activity. The prediction of this study is that as pH increases (becomes more basic), catecholase reaction rate will decrease. Materials and Methods Catecholase activity was determined as described by Ainsworth et. al. (2010) in the BI 112 Lab Manual. Specifically, three reactions were set up using buffers with pH 7, 9 and 11. The reaction with pH 7 was used as a control. Each tube contained 1 ml of potato extract, 6 ml of pH buffer, and 3 ml of catechol. Tubes were covered in parafilm and mixed thoroughly as each reagent was added. For each tube, catechol was added last to prevent the reaction from beginning prior to data collection, and each reaction was conducted in triplicate. To determine the amount of benzoquinone produced, a color chart corresponding to benzoquinone concentration (Figure 1) was used

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