This is a two day lesson series using Hexbug toys bought at the local drugstore with magnets glued onto the front of each bug to simulate bonding sites. I worked again with WestEd to implement the lesson for the first time this school year and expanded upon it once I saw just what a valuable experience it was for the students.
During Day 1, students utilize Hexbugs to simulate the work of DNA polymerase. They collect data on their trials using the enzyme vs. without the enzyme and construct graphs of their data.
Standards: SL.9-10.1, SL.9-10.1c, RST.9-10.3, RST.9-10.4, HS-LS3-1, SP1, SP2, SP3, SP4, SP7, SP8 XC-P-HS-1, XC-SF-HS-2
During Day 2, students brainstorm and conduct their own trials to test a variety of variables that might impact enzyme action. We wrap up together as a class to make the connections between their data and observations, the basics of enzyme-catalyzed reactions, the limits and benefits of models, and the specific substrates and enzymes involved in DNA replication.
Standards: W.9-10.1e, SL.9-10.1, SL.9-10.1c, RST.9-10.3, RST.9-10.4, HS-LS3-1, SP1, SP2, SP3, SP4, SP7, SP8 XC-P-HS-1, XC-SF-HS-2
I piloted this lesson last month unsure about the timing--should I have used it earlier when we studied the basics of enzyme work? Are the model analogies strong enough to make sense? Will the data actually emulate what we would expect to see in real life in terms of a short time frame for product production in the presence of an enzyme?
After using the lesson with students and getting feedback from students, it is clear that this lesson is a great way to circle back to the basics of enzyme action that we worked with during the first semester. Students were able to connect their knowledge and expand it into the specifics of DNA replication. I don't believe that the conversations we would have had about experimental design, model limitations and connections, or their understanding of exactly how enzymes reduce the time frame for chemical reaction product synthesis would have been possible that much earlier in the year. Depending upon my students next year, I could envision spacing out the two days so that the first part of the lesson happens during the first semester and the second as a lesson we use to reconnect and expand later on during this spring semester lesson. I am excited to hear about your experiences with this lab!
My deepest appreciation to the staff at West Ed including Jodi Davenport, Matt Silberglitt, and Jacqueline Powers along with the generous project funders:
1. Ask students to take out their Catalysis Investigation Worksheet from yesterday. Tell students that you heard so many great questions about enzyme function the reaction rates that you wanted to give them some to investigate some of the things they were curious about.
2. Pass out their brainstorming document for today's investigation. Ask students to move to their lab tables with both documents.
3. Tell students that each lab group will be investigating one specific variable that they think could impact DNA polymerase activity/rate of reaction in their experimental chamber. Review with them the enzyme prompt responses they generated yesterday.
4. Tell students they will have the next ten minutes to decide upon their variable and record their experimental design on the brainstorm document. Circulate among each group to help kids design an effective experiment and support them as they work to identify their independent variable, dependent variable, and best practices for a controlled experiment.
1. Once you have checked in with each group, announce that they can begin to work on their experiment using the materials/set up listed on the Hexbug Enzyme Investigation materials document and seen in use in the lab set up.
2. As students work, walk around to each group to encourage, question, and trouble shoot as needed. Students will work continuously with focus and attention throughout this session due to both the highly engaged nature of the Hexbug toys as well as the curiosity about the outcome of the experiment they designed themselves.
3. As you might have noticed during Day 1 of this lesson series, the experiment portion of this lab session goes very quickly. Let students know that when they finish their experiment and data recording and discussion, they can work on their graphs from yesterday or tackle another variable listed on their brainstorming document that they wish to investigate.
1. Ask each student group to reflect upon the following prompts:
What variable did you and your team decide to investigate?
What were your results?
Identify your independent and dependent variable.
How did you create a controlled experiment?
How would you improve upon your experimental design?
What other variables are your curious to learn more about in relation to enzyme activity?
2. Using the spokesperson protocol, have each group share out their responses to a maximum of 2 of the prompts above.
Students will share that they investigated/wanted to investigate: substrate concentration, enzyme concentration, the concentration of over things (represented by pens, erasers, etc.), a larger cell space (represented by a box lid), different speeds of substrate movement (battery strength). Because of the brainstorming work we did at the start of class, all student groups were able to correctly identify their independent and dependent variables and to describe their controlled experiment.
Students continued to be curious about the speed of movement of the substrate Hexbugs--was their an ideal speed? Is faster always better? Is it different for each substrate? Why?
3. Tell students that they will be using the prompts above to create a conclusion statement about their lab investigation. Ask students to begin to outline their statement now for the remainder of the class period. Remind them that although they may collaborate with their team as they discuss each prompt, that their writing is their own and must be written in their own words.
4. This typical student work sample shows a strong connection between our prompts and the specific student investigation being described. Based upon their writing, all students came away with an deeper understanding of how enzymes work to bring different molecules close enough to each other to form bonds and I loved the depth and range of questions they had based upon what they observed and discussed throughout their investigation. I think that the next time I use this lesson, I will include a more specific prompt to get deeper into the structure of enzymes and how that impacts their function.