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AP Biology
Ms. Ellis
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Pop-It Bead Enzyme Activity1
This activity is designed to give you a hands-on experience of enzyme kinetics.
In this activity, one member of the group will act as a protease, an enzyme that digests
proteins. The “enzyme” student will act as many proteases do: she will break a peptide
bond following a specific amino acid. Peptide bonds between other amino acids are not
susceptible to breakage by this enzyme. Because many of your digestive proteases work
this way, you produce several different proteases in order to fully digest the proteins that
you eat into separate amino acids.
Before coming to lab:
Read through the procedure and set up appropriate data tables on the blank pages
at the end of the lab handout.
Materials
1 small brown paper lunch bag
1 stopwatch or timer
Pop-It beads of at least two different colors, one of which is red
1 pair mittens or gloves
Procedure
1. Open the paper bag and leave it standing open on the bench or desk.
2. Create 10 strands of beads, each made up of 11 beads total. Each strand must contain
one and only one red bead, and the red bead can be located at any point in the strand.
(To simplify this activity, do not put any red beads at the end of a strand so that their
knob is not attached to another bead. You may put them at the other end of a strand,
though.)
3. What is represented by the beads?
What does each strand represent?
4. Place the 10 strands in the paper bag.
5. One student is designated as the enzyme. This enzyme catalyzes the breaking of the
strand by separating the knob of a red bead from whatever bead that knob was
inserted into.
6. Another student is designated as the timekeeper. She will run the timer using the
“count up” function. Check to make sure the timer is set to “count up”.
Modified from “Making the Rate: Enzyme Dynamics Using Pop-It Beads” by Frances R. Ragsdale and
Kay M. Pedretti. The American Biology Teacher, vol. 66, no. 9, pp. 621-626 (2004).
1
7. When the timekeeper begins timing, the enzyme will reach into the paper bag without
looking and pull out whatever she first encounters. If there is a red bead in the strand
she pulls out, the enzyme should bread the strand as described in step 5 above.
Why should the enzyme not look into the bag? How is this like a real enzyme?
8. After a strand has been broken, both parts of the strand are returned to the bag. The
timekeeper or another student in the group should record that one cut has been made.
9. The enzyme continues to reach into the bag, pull out whatever she first encounters,
and break the strand if possible. Remember that only one strand can be removed
from the bag at a time. Strands that have already been cut and thus do not have a red
bead inserted into another bead must be returned to the bag unchanged.
10. As the enzyme continues to make cuts, the designated student continues to keep track
of how many reactions have been catalyzed (i.e., how many cuts have been made).
11. As soon as the tenth cut has been made, the timekeeper should stop the timer and
record the amount of time it took to make 10 cuts. The time should be recorded in
seconds.
12. Using your data, determine the rate of enzyme activity, which should be expressed in
cuts/second. Please note that rate is not equal to the average time it takes per cut.
Record your rate in your data table.
13. Repeat the procedure, but this time have two red beads in each of your strands at the
beginning. Each strand should have 12 total beads (2 red and 10 non-red) this time.
Note that the enzyme will continue until 10 cuts have been made, even though not all
red beads will have been separated from their neighboring beads at that point.
14. Repeat the entire procedure, this time with 3 red beads per strand and 13 total beads
in each strand.
15. Repeat the entire procedure, including runs with 1, 2, and 3 red beads per strand, with
the enzyme wearing gloves or mittens.
What do the gloves or mittens simulate?
Data Analysis
1. Each student should make a graph of her group’s data. Use rate, not time, on the
appropriate axis. Review the criteria for a good graph if you do not remember them.
2. Graph the glove/mitten data on the same set of axes as the regular data.
3. Attach the graph to the lab before handing it in, and put your name on it.
Analysis Questions
1. What was the substrate in this activity?
2. What happened to the rate of enzyme activity as the substrate concentration
increased? How do you explain the effect? Is this consistent with the effect substrate
concentration has on real enzymes?
3. Draw the shape you would expect the curve to take if you increased red bead
concentration further. Label but do not number your axes.
4. The mittens or gloves were meant to simulate what happens when an enzyme is in
less than ideal conditions. Name at least two environmental factors that could impact
the rate of function of an enzyme, and explain why they affect rate.
5. Write a single paragraph describing what you actually did in this activity, including
the action of the enzyme, what changed from trial to trial, and how the changes
affected the amount of time it took to make 10 cuts. Give enough information that
someone could read it and replicate your work. Use terms an 8th grader could
understand, like bead and amount. Then re-write the paragraph substituting in
scientific terms, such as substrate, rate, and concentration. You do not have to
squeeze your answer into the space below. Use the blank pages at the end of the lab
if needed. You must turn in both paragraphs!