Beacon Lesson Plan Library

Toothpick Breakdown

Beverly Grim


Students model the activity of an enzyme acting on a substrate and observe relationships.


The student knows that complex interactions among the different kinds of molecules in the cell cause distinct cycles of activity governed by proteins.

Creates potential solutions to industry problems using math and/or scientific concepts and communicates solution using industry appropriate language arts and graphic skills.


-Forty toothpicks per two-student team
-Watch with a second hand
-Graph paper


1. A discussion on proteins, enzymes and substrates

2. A discussion on rate and factors that affect the rate of a reaction


The student
-knows that complex interactions exist among molecules within the cell
-knows that distinct cycles of activity are governed by proteins
-knows that concentration of substrate affects the rate of protein synthesis
-knows that enzymes and substrates interact within the cell
-understands the principles of enzyme kinetics
-describes the "lock and key" model and identify the active site and substrate
-understands the concept of induced fit
-understands the process of denaturation

1. Divide students into groups of two.

2. Distribute 40 toothpicks to each student team. Explain that the toothpicks represent a substrate.

3. Explain that one studentsí hands represent an enzyme that breaks down this substrate; The enzyme will be called toothpickase.

4. Have one student from each group pick up a tooth pick and break it. Explain that the place where the toothpick fits within the hands represents the active site of this enzyme.

5. Have one student from each group pick up and break a toothpick as fast as they can while the other member of the group times the activity. Tell students that even at the faster speed, it still takes time to break the toothpick. This is the initial maximum velocity (Vmax)

6. Have students place the toothpicks in a pile. One member of the team should break as many toothpicks as
possible, in 10 seconds. Count each toothpick as it breaks. Record the number of broken toothpicks in a data table.

7. Have students put the broken pieces back into the pile of unbroken toothpicks. Explain that during a reaction, products and reactants are mixed together.

8. Have the students continue to break and count toothpicks for another twenty seconds. (Only whole toothpicks should be broken, not pieces of broken toothpicks.)

9. Have students add the number broken in 20 seconds to the number broken in ten seconds and record the total in the data table.

10. Have students replace the broken pieces in the pile of unbroken toothpicks.

11. Instruct students to continue to break and count toothpicks for another 30 seconds, Add to the previous total and record in the table.

12. Have students return the broken pieces to the pile of unbroken toothpicks.

13. Ask the students to continue breaking the whole toothpicks for another 60 seconds. Do not give them any
additional toothpicks. Record the total in the data table.

14. Have the students graph the number of toothpicks broken as a function of time.

15. The students should answer questions and draw conclusions concerning the model.


The following items may be used in the assessment of the student projects:

Data Table
* Title
* Complete (time and number of toothpicks metabolized)
* Accurate

* Title
* Labels are on appropriate axis
* Intervals are appropriate to scale
* Accurate line graph
* Neat appearance

The following questions may be posed to help assess student understanding:

1. How is this like the lock and key model?

2. How is rate affected by concentration?

3. What other factors may affect rate?

4. How would spreading out the toothpicks affect rate?

The following test questions may be used to assess students understanding of the material:

1. Which model best describes the interactions between enzymes and substrates?
a. hand and fist
b. foot and sock
c. lock and key
d. oil on water

( answer c. The substrate fits within the enzyme very much as the key fits within a lock.)

2 Which factors may effect the rate of a reaction?
a. heat
b. concentration
c. catalyst
d. all the above

(answer d. These all affect the rate of a reaction)

3. Based on the activity, which term best explains the functions of our hands?
a. a working active site on a substrate
b. a working active site on an enzyme
c. a working substrate on an enzyme
d. a working substrate on a protein

(answer b. The hand represents the enzyme; the place where the breaking takes place would be the active site.)

4. According to the activity, increasing the number of toothpicks would affect the rate in which way?
a. It would increase the rate.
b. It would decrease the rate.
c. It would not affect the rate.
d. iIt is impossible to predict.

(answer a. Increasing concentration increases rate. )

5. Why does our hand and toothpick model illustrate the induced fit model?
a. The hands fit together.
b. The toothpicks are in an induced pile.
c. The hands move to fit the toothpick.
d. The toothpicks are broken and placed in the pile.

( answer c. The hands move to induce a fit).

This model represents the relationships between enzymes and substrates. It should demonstate the influence of concentration on reaction rate. As concentration drops, reaction rate will slow down. Other factors that effect the rate include temperature, pH, surface area and catalysis.

This model is an excellent model to show induced fit because the active site could be reshaped to break the toothpicks

To calculate the initial reaction rate and the final reaction rate, use the formula y2 - y1/t2 - t1

Can you think of other ways to adapt this analogy to the current model of enzyme kinetics?


Attempt the same experiment after mixing toothpicks and paper clips. A decrease in rate should be noted.
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