Lactose and Lactase: Exploring Enzymes as Catalysts (page 2)

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Author: Beth Touchette


In the first experiment, you shouldn’t have found any glucose in the plain glass of milk, and you should have found the same amount of glucose in each of the two glasses of milk mixed with lactase. In the second experiment, the glass of milk with baking soda and lactase probably produced less glucose than the glass that had only lactase added to it. The glass of milk with added vinegar should have produced slightly more glucose than the glass that had only lactase added to it.


Normal milk doesn’t have any glucose—just lactose. This is why you didn’t find any when you tested the glass. You should have found glucose in the other two cups, but why wasn’t there more in the cup that had more lactase added to it? Remember, lactase is an enzyme, and we describe enzymes as catalysts: a substance that helps chemical reactions happen without being used up. Each bit of enzyme can break down multiple molecules of milk sugar, so as long as you stir the glass and wait long enough, even a tiny bit of the enzyme is enough to break down all the lactose in the milk!

Now let’s figure out how we can explain the results of our second experiment. Lactase goes to work in your stomach and small intestine, where there is also lots of acid. The lactase enzyme is not affected by the acidy vinegar which might even help the lactase do its job better. Baking soda, on the other hand, is a base, and we don’t find a lot of basic substances in our digestive systems! Basic compounds like baking soda can damage enzymes like lactase, preventing them from working as well.

What other variables can you investigate? Try to see how heat and cold, and other chemicals affect how well lactase works!

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