Lab Report: Enzymes Are Highly Selective

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[. . .] However, as the temperature rose above 60 degrees, the rate of reaction gradually decreased; the temperatures between 80 and 100 degrees Celsius were too hot resulting in denaturation of the protein making it non-functioning (Schneider, Corona, Rosales, Schneider, Rodriguez, & Pineda, 1990). Besides, temperatures above 80 degrees Celsius resulted in more energy which disfigured the enzyme's active site making it lose shape and subsequently stopping the reaction. The major challenge of this experiment is that it is difficult to see the color change due to the milk used and time when this color change exactly occurs. In addition, the test strips colorations may have been interpreted incorrectly due to human error. Also the handling of tubes could have caused the temperatures to be different than stated. There is a possibility of the tubes warming from too much before reading, leading to skewed results. Observing the effects of temperature on the production of glucose, it can be concluded that the optimal level for activity of the production of glucose is at temperature level of between 40 and 60 degrees Celsius. The results for optimal temperature for enzymatic activity may not be accurate due to varying interpretation of the color by different people as well as human errors during the addition of lactase with the pipette. In addition, were the tubes to be placed in the water bath for long, the temperature results could show different results; thus, a repetition of the experiment can be initiated to bring different accurate results.

Fluctuating low and high pH levels results in loss of enzymatic activity as they result in changes in the shape of enzymes' active sites. Looking at the results it can concluded that when the pH was about 7, glucose production was at optimum with an output of 500mg/dL. Besides, between pH 2 and7, enzyme lactase was catalyzing the reaction at the maximum rate and greatest amount of glucose was produced (Naim, Sterchi, & Lentze, 1987). In addition, pH levels above 10 and 12 led to a decline in the amount of glucose produced; at this pH, ionic bonds holding the tertiary structures of enzyme lactase within the active site broke resulting in low reaction. Moreover, at pH above 10, the lost their shape as became non-functional. At this high pH, the substrate molecules were unable to fit into the enzyme's active sites and enzyme-substrate complexes could not be formed and the reaction stopped. Observing the effects of pH on the production of glucose, it can be concluded that the optimal level for activity of the production of glucoseshould be a pH level of 2-7. . In addition, misinterpretation of the color changes and human errors during addition of lactase with the pipette may be issues during formulating the results. Additionally, placing the tubes for a long period of time could affect the pH results and therefore, re-working on the experiment is recommended. After examining the temperature and pH results for this enzyme it is possible that it may have come from both bacteria and human.

The enzyme lactase is specific to lactose as opposed to maltose to a greater degree. The amount of glucose produced from the lactose tube is 1,000mg/dL which is two times greater than the amount in the maltose tube which is 500mg/dL. Lactase is an enzyme that is specific to lactose; it wraps around the lactose substrate breaking it down into galactose and glucose (Fernandez, Canada, Jiminez-Barbero, & Martin-Lomas, 1995). However, lactase is not fully specific to lactose since the tubes containing maltose produced some glucose; maltose thus, can also bind to the enzyme lactase just like lactose. It can be concluded that if lactose were specific to lactase only, then maltose would not have produced any glucose. But it prefers lactose as a substrate because more glucose was produced using lactose.

EDTA removes the ions that lactase needs to function as an enzyme. If enough EDTA is added, lactase will no longer have any of its ion cofactors to aid in the breakdown of lactose. The use of EDTA resulted in low enzymatic activities as opposed to the tube containing distilled water and milk (Sallee & Clapper, 2007). In this tube, the enzymes' co-factors were not disrupted leading to functioning at optimum temperatures thus higher output. The addition of EDTA in the other tube inhibited the activities of the co-factors resulting in low enzyme activities as shown in the table above. EDTA reduces enzymatic activity as indicated by absorbance is consistent with the premise that the enzyme acts as a catalyst for the oxidation reaction. In addition, it is clear that EDTA blocks the cofactors from entering the active sites making lactase unable to catalyze the hydrolysis of lactose, the result being low production of glucose. The results may have been affected by human error during the reading of glucose test strips and besides, the EDTA may have been dilute and thus unable to bind to the cofactors; magnesium and calcium. The other problem is that the EDTA used in the experiment could have stayed for a limited duration and could not fully bind to lactase and remove the cofactors within milk.


Cornish-Bowden, A. (2004). Fundamentals of Enzyme Kinetics. Portland Press.

Dunaway-Mariano, D. (2008). Enzyme Function Discovery. Structure, Vol.16 Issue 11, 1599-1600.

Fernandez, P., Canada, J.F., Jiminez-Barbero, J., & Martin-Lomas, M. (1995). Substrate Specificity of Small-Intestinal Lactase: Study of the Steric effects and Hydrogen Bonds involved in Enzyme-Substrate Interaction. Carbohydrate Research Volume 271, Issue 1, 31-42.

Naim, Y.H., Sterchi, E., & Lentze, M. (1987). Biosynthesis and Maturation of Lactase-Phlorizin Hydrolase in the Human Small Intestinal Epithelial Cells. Biochemical Journal Vol. 241 No. 2, 427-434.

Sallee, J., & Clapper, A. (2007). The Effects of Temperature and Chelating Agents on Catechol Oxidation.… [END OF PREVIEW]

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Enzymes Are Highly Selective.  (2012, November 8).  Retrieved April 25, 2019, from

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"Enzymes Are Highly Selective."  November 8, 2012.  Accessed April 25, 2019.