The Effect of Carbohydrates on the Reaction Rate of the Enzyme Catecholase

Introduction

Enzymes are protein catalysts that are present in all living organisms (Ainsley, 2010). They are responsible for all of the chemical reactions that take place by lowering activation energy and speeding up reactions. However, the rate of reaction can change depending on if there are factors such as enzyme and substrate concentration, temperature, carbohydrates, pH, etc that affect the enzymes. Catacholase, the enzyme used in this experiment, is the enzyme that causes browning in fruits and vegetables once they are exposed to oxygen. This browning is called benzoquinone (Lunadei, 2011). In this experiment, we will examine the rate of reaction of catecholase with the addition of the carbohydrates sucrose, starch, and fructose. It has been found that putting fruit into sugar solutions can slow enzymatic browning (Brain, 2000). The prediction is that since the same amount of carbohydrates are used for each set, the reaction rates will most likely be very similar and the rate of reaction will increase slowly and then level out due to the sugar denaturing the catecholase.

Materials and Methods

Nine test tubes were set up, three for each carbohydrate in case of errors. We used 1 M sucrose, 1% starch and 1 M fructose. In each tube was 1 mL potato extract, 2 mL of catechol and 3 mL of the carbohydrate. The catechol was added last so that the data could be collected at 0 minutes. The tubes were then covered with parafilm and mixed. We determined the amount of benzoquinone that was produced by using the color chart (Figure 1) provided by Ainsworth et. al. (2010). We began the timing at 0 minutes and checked the production of benzoquinone by matching the test tubes to the closest color on Figure 1 every minute for five minutes. For every carbohydrate group, the average amount of benzoquinone was calculated. The reaction rates were found by first finding the rise and then the run on the line and then finding the slope (rise/run). The control group was Tube 1 from the first experiment where water was used instead of carbohydrates.

Results

Figure 2 shows the average amount of benzoquinone for each carbohydrate. For all three carbohydrates, sucrose, fructose and starch, the results were the same. At 0 and 1 minute(s), the production was 0, at 2 minutes, it jumped to 2, and at minutes 3-5, the production leveled out at 3. Figure 3 shows these plotted points. The catacholasse reaction rates for each carbohydrate (shown in Figure 4) were found to be 1.5 - the rise was 3 and the run was 2 so the slope equals 1.5.

Discussion

The predictions that the carbohydrates would slow down the reaction rates and since the same amount of carbohydrates were used for each test group that the result would be similar were supported. All three carbohydrates caused the reactions