Download Enzyme Lab:

Bio A/H - Biochemistry
Got Milk?
Enzymes are specialized proteins that make it possible for our cells to perform all of the chemical
reactions that they need to. Simply put, each reaction that occurs in the body has a cost. The currency for the
cell, however, is not dollars and cents, but rather energy. The more energy a reaction requires, the harder it is
for the cell to perform. The energy required to complete a chemical reaction is called the activation energy.
Enzymes make it easier for the cell to perform a chemical reaction by lowering the required amount of
activation energy. .
Carbohydrates are a group of compounds used by the body for simple, fast energy. Sugar and starch are
two examples of carbohydrates. Some of these carbs are very large molecules, like starch, which need to be
broken down into much smaller units before they can be used. Another example of a carbohydrate that needs to
be broken down is the disaccharide, or double sugar, found in milk, called Lactose.
Lactose is made by combining two monosaccharides: Galactose and Glucose. In order for your body to use the
lactose it must first break it down into one molecule of glucose and one molecule of galactose. The
monosaccharides are what the body actually needs. To make life easier, your body enlists the help of an
enzyme to break apart lactose. This enzyme is called Lactase and the reaction is shown below.
Directions:
1. Obtain a sample of regular milk, pour 30 mL into the reaction beaker
2. Use the Glucose test strips to determine if there is any glucose in your milk sample. Dip the strips in
the milk for 1-2 seconds and quickly remove. Wait about 1 minute, then record your results.
3. Obtain 1 Lactase Enzyme Supplement tablet and GENTLY crush the tablet in its packet.
4. Add the Lactase Enzyme powder to your sample of milk and mix.
5. When you are finished, leave your milk/lactase solutions in their beakers and return to your seats. At the
end of the period, we will test our solutions once more with the glucose strips.
Clean up: dump milk mixture down the sink and rinse cup; DRY and return the cup to your station;
throw out any used test strips; wipe up any spills or lactase powder with a wet paper towel.
Data collection:
Glucose levels before lactase:
_____________ (units??)
Glucose levels after lactase:
_____________ (units??)
Bio A/H - Biochemistry
Questions to consider (and by that, I mean do for homework)
1. What was the change you observed after you added lactase to the milk? (HINT: look at the data you
recorded)
2. What is the substrate in this chemical reaction? What are the products? What is the enzyme?
3. In your own words, explain what happened after you added lactase. Why did your milk test positive for
glucose AFTER we added the enzyme?
4. We know that we have to be able to digest macromolecules before we are able to use them. Many people
are unable to drink milk because they are “lactose intolerant”. Explain why you think people become
lactose intolerant. How does this relate to substrates being “site specific”?
5. Starch is a polysaccharide that is made up of chains of glucose monomers. Do you think a starch
solution would test positive for glucose after adding lactase? Why or why not?