Using Toys to Explore Enzyme Activity in DNA replication (Day 1 of 2)
Objective
Big Idea
Notes for the Teacher
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:
- This material is based upon work supported by the National Science Foundation under grant DRL-1108896 and by the Institute of Education Sciences, U.S. Department of Education, under grant R305A120047. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation, the Institute of Education Sciences, or the U.S. Department of Education.
- For more information about the models, check out the website West Ed set up just for this project!
The Classroom Flow: Introducing the Activity
1. Ask student lab groups to briefly discuss the following prompt:
What do you know about enzymes? Discuss as many ideas as you can!
2. Using the spokesperson protocol, have student groups share out their responses and list them on the whiteboard.
Note: The main ideas that the students should generate include:
- an enzyme's active site connect with a substrate to form products through chemical reactions
- types of reactions (catabolism and anabolism), examples of enzymes (suffix -ase)
- enzymes are catalysts because they decrease the time needed to produce products of a chemical reaction
- enzymes do this by lowering the activation energy needed for a chemical reaction to proceed
3. Remind students of the work we have been doing throughout the unit using models as a way of digging deeper into the structure and function of complex molecules. Tell students that today they will be investigating the way enzymes work using an activity focused on DNA polymerase, the enzyme involved in our recent exploration of DNA and DNA replication.
The Classroom Flow: Working with Toys
1. Pass out the Catalysis Investigation Worksheet for this enzyme simulation.
2. Show students the materials they will be using. See my teacher materials support document for help in getting together the simple materials needed for the lab. Each student group of four receives one set of materials. Before starting this activity, take a look at this short video clip showing how the toys represent monomers being forced into proximity by the active site of the sticky note enzyme in order to create a bond more quickly.
3. Allow student groups to work with the toys and collect their data.
- Note: At this time in the school year, I do not assign roles to student lab groups as they are pretty self-reliant and eager to dive in, especially when we are working with novel materials like these Hexbug toys. If I have specific groups that need more guidance, I write on the board and announce potential suggested roles: data collector, data recorder, materials manager, and project manager. As I initially circulate around the room, I check in to ensure that each group has a plan for their work and prompt any groups that might be struggling to assign my official roles. At this time in the year, that is a rare need of students but if I were doing this lab earlier in the year, I would assign them formally as a requirement in each group.
4. As you circulate, encourage students to talk about their data--they will be surprised to see that the use of the enzyme really does lower the reaction time! The student work sample is a good representation of the type of data and answers most students should be able to give after completing this activity.
- If you have a rare student group that does not get to see this general truth in action, encourage them to do more trials.
- You can also talk with groups about ways to improve the experiment (more trials, throwing out the highest and lowest trial values, etc.).
- Discussing the limitations of the model and having ways to get around those areas of concern is really empowering for students. Other observations that might come up center on the speed of the toys--they are no all the same. I kept extra batteries on hand to navigate the speed issue if a group wanted to explore it further and I also encouraged students to check in with other groups for comparison. For some groups, I mentioned our upcoming extension tomorrow and asked them to think about ways they could really dig in to their question deeper in the next class period rather than our final five minutes of investigation today.
- Allow a bit of time for student to play around with their materials! When students explore their materials, they will have a better set of observations to draw from when they are designing their experiments and formulating their own unique questions of interest.
The Classroom Flow: Creating Graphs and Connecting the Data to the Big Idea
1. Pass out graph paper or ask students to take out their own.
2. Tell students that they will be creating a graph of their group results. Pass out the basic graphing guidelines document for review.
Note: At this time in the school year, my expectation is that this is all the guidance they should need in order to create an appropriate graph. I will circulate in order to make sure that individual student groups are on the right track and question their choices if they are not.
3. Circulate around the room to help support students as they work on their graphs.
Note: Questions that help guide students to determine the most appropriate graph type and necessary graph components could include ones like:
- for graph type: Do you think a line or a bar graph would be a better way to show your audience your data? Why? Is there any other way other than the one you are choosing that might be better?
- for a descriptive title creation: Can your audience figure out what this graph represents without having done the experiment? What might help them to know?
- for missing pieces such as units and variables: What other information could your graph include to help your audience understand the data?
- for general neatness/visibility/time and care: Is this your best work? What might make this graph better--more attractive to your audience and/or more easily understood by your audience?
4. Check out this typical sample student work graph. This student chose to draw a line graph and include points for each trial and the averages with and without an enzyme. It is an interesting conversation to compare student chosen and drawn line and bar graphs to discuss the merits and drawbacks of each format. This graph has all of the necessary parts: color/ruler, descriptive title, labeled x and y axes (units and variables), and a legend.
The Classroom Flow: Prepping for Tomorrow's Work
1. Tell students that tomorrow they will be working with the toys again to investigate other factors that could influence enzyme activity in our lab.
2. Ask student groups to briefly discuss the following prompts:
What could you do in your experiment chamber to speed up the rate of reaction even more?
What things could influence the rate of enzyme activity?
3. Using the spokesperson protocol, have student groups share out answers while you document them on the board.
4. Announce that student groups should each decide upon one variable they would like to investigate tomorrow and begin to discuss how they should set up their experiment in order to do that. Give them the remaining class time to start this process and let them know they will have an additional 10 minutes tomorrow to construct their experiment before beginning our investigation.
And now on to Day 2!
