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.
In this activity, candy corn modeled the lipid molecules where the yellow part is hydrophilic and the orange/white portion is hydrophobic.