P-Nitrophenol Reaction Lab Report

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In this experiment, absorbance at A400 was directly proportional to the number of moles of p-nitrophenol. This shows that there is a linear relationship between the absorbance and the number of moles of p-nitrophenol, which later also shows that there is a linear relationship between the absorbance and the concentration of the p-nitrophenol, as the number of moles of p-nitrophenol will increased when the concentration of p-nitrophenol increased. The R2 value obtained for the standard curve is 0.9997, which indicates that the data obtained fit the line of best fit, showing that the data are accurate. The values of absorbance per µmol of p-nitrophenol were then obtained from the gradient of the curve, which will later be used in calculation in determining the enzyme activity. Based on Graph 3, it was shown that the enzyme activity of alkaline phosphatase increased with the increase of MgCl2…show more content…
The alkaline phosphatase has a lower enzymatic activity when pH 7 and 7.5 Tris-HCl were used; whereas the enzyme has a higher enzymatic activity when pH 8, 8.5 and 9 Tris-HCl were used, with the enzymatic activity at pH 9 being the highest. This shows that the alkaline phosphatase works optimally at alkaline condition such as pH 9 (Kaslow, n.d). The results of the graph show that alkaline phosphatase work less optimally at lower pH, this may due to at lower pH, the positively-charged amino side chain of the peptide sequence of alkaline phosphatase will release the hydrogen ions, therefore causing the tertiary structure of the enzyme altered, which will causes conformation change in alkaline phosphatase’s active site. Thus, the substrate p-nitrophenyl phosphate will experience some difficulties to bind to the binding site on active site of alkaline phosphatase, therefore decreasing the enzyme activity when pH becomes

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