Lactase Enzyme Lab Diana Kisseleva, Molly Gilbert, Emily Hayes


Heat plate: take precautions when using the heat plate so that you do not burn yourself

Eye Protection: you must wear goggles at all times while performing the experiment. This is so that chemicals do not end up getting into your eyes.

Touching the Solutions and Liquids: This should be avoided, especially with the denatured enzymes. The denatured where boiled so may be hot and burn your skin.


The purpose of this experiment was to test the glucose levels in the five solutions we mixed, milk and enzyme solution, milk and water, milk and denatured enzyme solution, sucrose solution and enzyme solution, and finally, sucrose solution and water.


Enzymes are a class of protein molecules that act as biological catalysts. These catalysts increase the rate of a reaction, but are not used up in the reaction. Enzymes are very similar to chemical catalysts but have many differences, as well. Enzymes are more specific than catalysts, meaning that they recognize particular substrates and convert them into products. The enzyme we studied was lactase, in a reaction this enzyme catalyzes the hydrolysis of the lactose into galactose and glucose. In simpler terms, lactase helps digest and break down lactose which is found in milk and other dairy products. When someone is lactose intolerant it means that the body produces a lower amount of lactase that is necessary to digest lactose. In “lactose-free” milk lactase enzymes are added into it to hydrolyze the lactose before drinking it.

Materials and Procedures


Lactase Tablet, 15 mL of Skim Milk, Water, Sucrose, 100 mL graduated cylinder, 10 mL graduated cylinder, 3 400 mL beakers, 5 test tubes, test tube rack, marking pencil, timer, hot plate with a pyrex test tube, Glucose test strip, stirring rod


Glucose Testing of Solutions in Test Tubes A-E

Analysis of Data and Conclusions

Lactase is an enzyme whose primary function is to split the disaccharide lactose into galactose and glucose. In this reaction, the lactose and water are the substrates, and the galactose and glucose are the products. The results in the data above correspond to the test for glucose. It is a product of lactose hydrolysis (in which lactase breaks the chemical bonds in the lactose), and changes test strips from yellow to a light green. In this case, it was only the milk and enzyme solution that was glucose positive - this shows us that the enzyme successfully reacted with the lactose in the milk to create galactose and glucose. Lactose and sucrose have different “shapes” despite having the same chemical formula (C12H24O11), thus allowing one to react with lactase in the active site and the other to stay unaffected. The reason as to why the milk and boiled lactase solution had negative results on the chart is that the enzyme was denatured. Dramatically raising the temperature will effectively “kill” the enzyme, rendering it useless. Lowering the pH, on the other hand, would not have affected this enzyme at all (although other enzymes might be susceptible to change), as lactase is commonly found in the stomach which has a low pH to begin with.

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