Enzyme Test Lab Report

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For the first part, the qualitative polyphenol oxidase test (Table 1), we looked at 3 qualitative test tubes, where only test tube 2 turned orange since this tube had both the 40 mM dopa, the substrate and PPO enzyme extract. However, the test tube 3 did have a cloudy component because of the presence of PPO extract, but there was no color change. For a color change to occur, there needs to be a presence of both the dopa and PPO extract. Furthermore, we calculated the final concentrations of dopa using the C1V1=C2V2 formula for the control groups (test tubes 1,3,5,7) which was 0mM and the experimental groups (test tubes 2,4,6,8) which was 4mM (Table 2). A standard curve of dopachrome concentrations vs. absorbance at 475nm was generated …show more content…
Based on our experimental results, we can conclude that our hypothesis is correct (Graph 2). To further explain, there is a greater amount of the enzyme available for the dopa to interact with and will lead to more formation of dopachrome. The rate of the enzyme-catalyzed as measured by velocity, also showed a linear relationship (Graph 3) and the enzyme being a limiting reactant, so the reaction will proceed at a maximum velocity. When the substrate in in excess, more enzyme will produce more product at a higher rate since Vi will be equal to Vmax. However, the linear relationship will not hold if the dopa becomes the limiting reagent. In the Qualitative polyphenol oxidase test (Table1), only one of the three reactions formed an orange product. The orange product is formed because of production of dopachrome. For dopachrome to be produced, both the substrate (dopa) and PPO enzyme must be present. The reactions that only contained one of the two hence will not produce dopachrome. With just PPO, and no dopa, there is no substrate for the enzyme to catalyze, and therefore no color change will take …show more content…
However, looking at the r-squared values of Graph, 1 2 and 3, it shows a strong positive correlation since it is closer to 1 between the two variables. To further the study the effect of enzymatic browning, this is an essential component. In this lab, we study the conversion of the substrate dihydroxyphenylalanine (dopa) to dopaquinone quickly converted to dopachrome in the presence of oxygen. It is interesting how the direct product of dopa, dopaquinone was never really measured and neither was PPO extract enzyme. Furthermore, the differences between the dilution factors 1/5 to 1/10 was a factor of ½ similarity to 1/20 and 1/40 as displayed on the graphs. This might be due to collisions between the molecules. Since temperature plays a huge role by affecting the shape and activity of enzyme, it must be kept higher for the enzyme to not cause denaturation. During this lab, the enzyme was always kept in the ice-cold bath. Similarity, people put most fruits and vegetables in the fridge. Thus, putting cut open potatoes in a refrigerator would help keep PPO active and prevent enzymatic browning. In addition, Enzymes are controlled by two different types of inhibition; competitive and non-competitive. Competitive inhibition occurs when inhibitors compete with the enzyme substrate to bind to the active site. While Non-competitive inhibition is when the inhibitor binds to the active site that

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