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[answered] Lactase Enzyme Lab Purpose: This lab will examine the speci

Lab due in a couple of hours. I need help, Please.

Lactase Enzyme Lab




This lab will examine the specificity of an enzyme (lactase) to a specific substrate (lactose).


Students will observe the actions of the enzyme and how shape is important to enzyme reactions.


Students will also observe what will happen when the enzyme is denatured.


Materials Lactase tablets (included in lab kit) 15ml (1 tbsp. or 3 tsp) milk- any milk will do Water-used for dissolving the lactase tablet, dissolving the sucrose and boiling the


lactase Sugar-5g (1 tsp) Teaspoon Tablespoon three cups - used for dissolving the lactase tablet, dissolving the sucrose and boiling the


lactase 5 small cups/containers (must be able to heat them in microwave or place in pan of


boiling water) Clock or timer microwave or stove top glucose test strips (included in lab kit) utensil for mixing




Lactose, the sugar found in milk, is a disaccharide composed of glucose and galactose (both six


sided sugars). Sucrose, ordinary table sugar, is also a disaccharide composed of fructose and


glucose, Glucose is a six-sided sugar and fructose is a five-sided sugar.


Lactase is an enzyme that breaks lactose down into galactose and glucose. Lactase can be


purchased in pill form by people who are lactose intolerant. These people lack the enzyme,


lactase, and cannot break down the sugar lactose into its component parts.


Although lactose is similar to sucrose, lactase will break down only lactose because of the shape


of the sugar.


In this lab, you will see lactase break lactose down into galactose and glucose. You will also


observe what happens if the shape of lactase is changed due to heating. Solution preparation


1. Enzyme solution: Add one lactase tablet to two hundred milliliters (6.5 oz) of water. Stir


until the tablet has dissolved.


2. Skim milk: this solution contains the lactose


3. Sucrose solution: Add 5 grams (1 tsp) of sugar to 100ml (3.5 oz) of water. Stir until the


sugar has dissolved.


4. Prepare a denatured enzyme solution


a. Place twenty milliliters (1.5 tbsp) of enzyme solution that you prepared above into


a small container (one that can be heated either on the stove top or in the


microwave. ex small glass or metal measuring cup.)


b. Add two hundred ml (6-7 oz) of water to a container that can be placed on the


stove top or in the microwave (the water must be high enough to come up over the


smaller container that you are heating. You are creating a hot water bath.)


c. Place the small container in the beaker or larger container. Place the larger


container and test tube or smaller container on the stove top or in the microwave.


d. Boil the water in the beaker for 30 minutes


e. Let the solution cool to room temperature


Lab Procedures:


1. Gather the materials


2. Label the small containers/cups with the following labels: A B C D E


3. To container A add 2ml of skim milk and 1ml of enzyme solution


4. Time for 2 minutes and test for glucose with the glucose test tape. Record this data in


table 1. If these was glucose present mark a ?+? in the table. IF glucose was absent, mark


a ?-? in the table.


5. To container B add 2 ml of skim milk and 1ml of water.


6. repeat step 4


7. To Container C add 2ml of skim milk and 1ml of denatured enzyme solution


8. repeat step 4


9. To container D add 2ml of the sucrose solution and 1ml of enzyme solution


10. repeat step 4


11. To container E add 2 ml of the sucrose solution and 1 ml of water


12. repeat step 4 Name _________________________________________ Date _____________ Lactase Enzyme Lab


Data Sheet


Glucose Test Results


Type of Solution


Test Tube A: milk and enzyme solution


Test Tube B: milk and water


Test Tube C: milk and denatured enzyme solution


Test Tube D: sucrose solution and enzyme solution


Test Tube E: Sucrose solution and water Glucose Test (+ or -) Conclusion and questions


1. Diagram and describe the lactose and lactase reaction 2. Why did the enzyme react to lactose but not to sucrose? 3. What happened when the enzyme was boiled? 4. Another way to affect the enzyme is by lowering the pH of the solution. However, lactase


is supposed to be able to work in the stomach. Would lowering the pH of the enzyme


solution affect the enzyme? Why or why not? 5. What type of reaction is this? Dehydration or hydrolysis? Enyzmes


For each question, click the circle next to the correct answer.


1. Without the presence of enzymes, the reactions necessary to sustain life would


require ___________________ in order to occur.


larger cells


higher temperatures


larger proteins


smaller atoms 2. Based on the graph, which of the following could be used to increase the reaction


rate beyond point C?


increase the amount of substrate


add more water


increase the temperature


decrease enzyme concentration


3. The part of the enzyme where the substrate binds is called the:


active site






large subunit 4. When a piece of liver is dropped into hydrogen peroxide, the peroxide bubbles


vigorously as a result of what reaction?


peroxide being broken into water and oxygen


peroxide is destroying germs in the liver


more peroxide is being created by the liver


liver and peroxide are joining together to make a new protein


5. Some people cannot digest milk products because they lack a specific enzyme.


Which enzyme would be used to break down the lactose in milk?








lactase 6. On the image, which letter represents the enzyme?










7. On the image, which letter represents the substrate?








8. On the image, which letter represents the product of the reaction?








D 9. In what way could you increase the rate of the reaction as it taking place in image C.


add more substrate


add more enzyme


remove enzymes


remove substrate


10. Enzymes are composed of what organic molecule?






fatty acids


proteins Lactase Enzyme Lab


Teachers Answer Sheet Teachers will be able to assess the results table (the only positive reaction should be test tube A)


and the teacher will be able to correct the conclusion questions.


Answer Key


1. the students should draw a hydrolysis-induced fit model


2. The shape of sucrose (glucose and fructose) is different from lactose (glucose and


galactose). The sucrose will not fit into the active site of lactose.


3. The enzyme denatured. The hydrogen atoms vibrated so much due to the energy added to


quaternary structure of the enzyme. Note: as long as the students understand that the


bonds broke changing the enzyme shape, they are ok.


4. The enzyme will denature (eventually). The H+ will interfere with the hydrogen bonds,


and denature the enzyme.


5. The reaction is a hydrolysis reaction.


Supplemental Information


Denaturing the enzyme was very difficult. We had to boil the enzyme (placing a test tube with


the enzyme in a beaker of boiling water) for 30 minutes.


We thought about lowering the pH of the enzyme solution, but commercial lactase is swallowed


and works in the stomach, so lowering the pH was not really an option for us.


We experimented by boiling the lactase for five, ten and fifteen minutes. Thirty minutes worked


for us. We suggest that you try boiling the enzyme before the lab, adding some milk (source of


lactose) and test for glucose. If glucose is present, boil the lactase for a longer period of time.


You can approach the enzyme specificity in two different ways:


1. Why didn?t the sucrose break down in the presence of lactase?


2. Why didn?t the lactose break own in the presence of boiled lactose?


This lab is an uncomplicated introduction to enzyme reactions.




This lab is a relatively simple lab which shows the specificity of enzymes based on shape. You


will need to purchase lactaid and glucose test strips. I suggest the glucose test strips from Science


Kits and Boreal Labs, which are easy to use.


You might want to set up the solutions before the lab (if you are pressed for time). This will


simplify the lab for the students.


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