Click HERE for the abbreviated lab report Instructions
The cell membrane is made of two layers of lipids. On each lipid molecule, there is a part of the molecule that repels water (hydrophobic) and a part that does not repel water (hydrophilic). The only way the lipid molecules could arrange themselves along the border between the inside of the cell (where there is water) and the outside of the cell (where there is also water) is to line up in two layers, back-to-back. The hydrophilic sides of molecules face the water in or out of the cell, while the hydrophobic portions are protected within.
In this activity, candy corn modeled the lipid molecules where the yellow part is hydrophilic and the orange/white portion is hydrophobic.
The role of the cell membrane is to regulate (control) what enters and leaves the cell, allowing some materials in/out while preventing other materials from doing so. In a similar way, a screen window allows certain things to enter/leave the home, yet prevents others from doing so.
A cell membrane allows some materials to either move into the cell or out of the cell, much like a screen window which allows some things into a home or out of the home.
The cell membrane prevents certain materials from enter the home or leaving the cell, just like a screen window prevents certain things from entering the home or leaving the home.
In each of the photos below, the students drew a picture or wrote out a quote/phrase in black permanent marker. Once the ink dried, they traced over their drawing or words in Crayola Magic Marker. Once that ink dried, they dripped water (a polar solvent) on the left-hand side of the paper and rubbing alcohol (a non-polar solvent) on the right-hand side. It can be seen that the Magic Marker ink dissolved in the water and not so much in the alcohol because it is a polar ink. As well, it can be seen that the permanent ink dissolved in alcohol and not in the water because it is a non-polar ink. Polar solvents will only dissolve polar solutes while non-polar solvents will only dissolve non-polar solutes.
<---Water (Polar) Alcohol (Non-polar)--->