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Enzymes Help Us Digest Food

In this hands-on, minds-on activity, students investigate the biological causes of Maria’s symptoms and Jayden’s symptoms. To explore the causes of these symptoms, students carry out two experiments and interpret the results, and they answer additional analysis and discussion questions.

Students learn about enzyme function and enzyme specificity as they figure out that Maria’s symptoms are due to lactase deficiency (resulting in lactose intolerance) and Jayden’s symptoms are due to sucrase deficiency.

In the final section, students are challenged to generalize their understanding of enzymes to interpret a video of an experiment with saliva, starch and iodine. This activity can be used in an introductory unit on biological molecules or later during a discussion of enzymes.

Download Student Handout: PDF format or Word format

Download Teacher Preparation Notes: PDF format or Word format

We invite comments on this NGSS-aligned Hands-On Activity and the accompanying Teacher Preparation Notes, including suggestions for other teachers who are planning to use the activity, useful preparatory or follow-up activities, additional resources or any questions you have related to the activity, or a brief description of any problem you might have encountered. If you would prefer to send your comments or questions in a private message, please write Ingrid Waldron at


iwaldron's picture

2023 revision

We have clarified and improved the instructions for the experiments, as well as many of the questions in the Student Handout. The Teacher Preparation Notes have been enhanced and clarified.

iwaldron's picture

September 2016 Revision

In the revised Student Handout, two of the experiments have been combined to reduce the amount of wait time and make it easier to complete all the experiments in one laboratory period. The revised Teacher Preparation Notes include more information about enzymes.

Carolyn Wilkins's picture

Are the files posted above

Are the files posted above the revised versions?

iwaldron's picture


The files posted above are the ones described in the comment above.

Sally's picture

urinalysis test strips

Can I use urinalysis test strips instead of glucose test strips, since they are less expensive.

iwaldron's picture

Urinalysis Test Strips and Updated Version of Activity

Yes, we have used urinalysis test strips with good success.

Also, I am working on a revised version of this activity, which I expect to have posted within a week. Meanwhile, if you would like to have the revised Student Handout and Teacher Preparation Notes, please email me at .


iwaldron's picture

2015 Revision

This revised activity is aligned with the Next Generation Science Standards (see page 2 of the Teacher Preparation Notes). One significant change is the addition of questions that analyze how the enzyme lactase functions in the digestive system and how the digestive and circulatory systems cooperate to provide cells all over the body with molecules that provide the energy for cellular processes.

Anna's picture

That is nice. Thanks for your

That is nice. Thanks for your explanation

Serendip Visitor's picture

enzymes help us digest food instructions for all three parts

I wanted to know if you can send the instructions for all three parts of the experiment "Enzymes Help Us Digest Food"?
Thank you, Carla Lowden

iwaldron's picture

instructions for all three parts

The procedures for all three experiments are described in the attachment available above.


iwaldron's picture

Using Lactaid Pills from the Drugstore

Tim Best reports success in using Lactaid pills instead of purchasing lactase enzyme.

"I've done 2 parts of the lab recently, and the store-bought lactase seems to work fine. I called Fisher Scientific, and found that depending on the batch the lactase they sell has somewhere between 12000-18000 lactase units per gram. The lactase from CVS is labelled as having 9000 units per pill, so I've just been dissolving 2 pills in 50mL of water, and having each group use 1mL of this solution. The glucose test strips are definitely indicating the presence of glucose when they should, although we've found that it does take more like 5-6 minutes as opposed to 3."

I welcome any additional feedback about this or any other suggestions.
iwaldron's picture

August 2012 revision

The main change in the new version of the Student Handout for this activity is that in the current version students design the second and third experiments. This will help to increase student understanding of the scientific method. If you would prefer to have explicit instructions for all three of the experiments, these are provided in an alternative version of the Student Handout. In addition, the Teacher Preparation Notes have been somewhat expanded and clarified.

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