There are many versions of this lab out there, most of them have the same basic idea. Students model enzyme activity by breaking toothpicks in half. They must only use their thumb and forefinger to break the toothpicks and they are timed at various intervals.

In my version, the students observe enzyme activity in normal conditions and when a competitive inhibitor is added (colored toothpicks). Enzyme denaturation is then modeled using masking tape to change the shape of the fingers, making it more difficult to break the substrate.

Students should observe that reaction rates slow down over time as substrate concentration (toothpicks) is reduced. A graph of products produced (broken toothpicks) should show that the number of broken toothpicks quickly increases and then slows as the number of substrate toothpicks decreases.

Analysis questions ask students to consider what would happen if you double the amount of substrate (toothpicks) and if you double the amount of enzymes (hands breaking toothpicks). Students are also asked to imagine a way you could model the introduction of a non-competitive inhibitor.

Grade Level: 9-12
Time Required: 30-40 minutes

NGSS Science and Engineering Practices 2. Developing and using models; 3. Planning and carrying out investigations 

HS-LS1-2 Develop and use a model to illustrate the hierarchical organization of interacting systems that provide specific functions within multicellular organisms