In and Out of Cells - Design Your Own
Lesson 12 of 18
Objective: Students will be able to explain how solutes and other materials move across membranes.
The Cell Processes unit is part 2 of my Cells 'R Us project based learning experience. Once the students are familiar with the structure of cells, we move on to how cells work. The lessons in this sequence are based on the "need to know's" created by the students (with guidance) for the Cells 'R Us project.
The complete sequence I use for the Cells 'R Us project is:
For this lesson you will need the 7 remaining "naked" eggs prepared before (In and Out of Cells Day 1). If you did not prepare them before hand, place 10+ eggs in a bowl and cover them completely with vinegar. Allow them to rest overnight.
Under gently running water, carefully rub the shells off the eggs leaving just the cell membrane. You will need one "naked egg" for each table/team, and one extra to be used a whole class control. The extra eggs are to allow for breakage when removing the shells.
Although the students were told the day before to bring their own solution to test, sometimes they "forget". It is useful to have things like soda (orange is the best), coffee, tea, salt and sugar on hand just in case.
To refresh students memories of what has transpired in class over the last few days, I play the following video, as I hand out the Says-Means-Matter sheets. See the connections the students made in these examples.
I display and hand out copies on the Movement across Membranes - Design Your Own sheet and go over the directions. Since I am asking the students to plan and carry out their own investigation (SP3), it is the perfect time to go over testable questions, identifying variables, writing hypothesis, etc. We clarify the expectations also by discussing the rubric (second page of the sheet), and discuss the potential areas where they might miss something and how to avoid it (peer review).
I remind the students that they must craft their experimental design before they gain access to the naked eggs, and that I must approve it. The approval will only come if every student that participated in writing the design is able to read and explain what they are doing and why.
I tell table "managers" to create a copy of the experimental design sheet that I posted on Edmodo, and share it with their table mates. I use Google docs for the experimental design sheet so that each member can edit the sheet simultaneously as they plan their investigation (SP3).
As the students are drafting their plan, I visit with them, and go over points of the scientific process, particularly as it pertains to writing hypothesis and identifying variables.
Once the teams have a complete experimental plan, I invite them over to the back table, where they have to tell me exactly what to do.
In the excitement of the experiment, students might forget a step, so they will need a reminder:
Teams of students that might finish this relatively quickly can visit Glenoe's Virtual Osmosis lab and/or GCSE's Bitesize Topic: Osmosis to deepen their understanding, or re-visit the active transport interactive.
To bring this lesson to a close, I ask for student volunteers to verbally share what solution they are using for their experiment, why they chose that solution, and what they expect to see when they come back the next day (hypothesis). This is a simple way to create interest in what other teams are doing.