Effect of pH on Enzyme Activity and Benzoquinone Absorption
Enzymes are partially or wholly proteins which help catalyze enzymatic reactions. As hypothesized, catechol oxidase (enzyme) was not able to function in a very acidic pH (pH 2) or a highly basic pH (pH 11). In both cases the catechol oxidase activity was decreased which resulted in minimum production of benzoquinone (product). Even though the original hypothesis was not completely supported, however, as seen in figure 1, the absorbance for the mixture is at its highest when the reaction occurs in the presence of a pH 8 buffer, which is close to the pH 7 originally hypothesized. The catechol oxidase is affected by the different pH concentration, and its most favorable pH value is pH …show more content…
The blue light was absorbed because the mixture in the cuvette had a dark brown color which prevented the transmittance of the blue color. The dark brown color of the mixture was due to the presence of benzoquinone. As hypothesized, when given time, the reaction between the 5mM catechol (substrate) and catechol oxidase (enzyme) continued and resulted in the production of benzoquinone. Because catechol and catechol oxidase were present in a favorable pH with no inhibitors, the catechol molecules gradually bind with the active site of catechol oxidase and were modified. Since the solution was mixed for a longer time, there were more impacts between the active site of the enzyme and the substrate molecules. This shows that in the presence of a small amount of enzyme the reaction continues until unless all substrate is converted to product, or the reaction is placed in an unfavorable environment like an acid or base. For this reaction, the maximum time given for the two molecules to react was 5 minutes, during which the absorbance kept increasing. However, over a longer period, the absorbance for the closed cuvette will stay constant because there would be no more substrate molecules left to modify and the graph will plateau (Reece, J.B. et al