To provide an accurate representation (model) of the molecular structure of the cell membrane for students who are studying Biology, and to build this structure utilizing the model.
A foundational theme in biology is the connection between structure and function. This is true both at the molecular and cellular level. The molecules which make up the cell membrane are phospholipids which do not dissolve in water. This property of phospholipids is vital in the formation of the cell membrane as the membrane is the structure which surrounds the cell.
The structure of the cell membrane is a double layer of phospholipids called a lipid bilayer.
Each phospholipid is composed of a polar “head” and 2 nonpolar “tails”. Polar molecules have a positively and a negatively charged end, while nonpolar molecules do not. The polar heads are attracted to water and the nonpolar tails are repelled by water. An example of a nonpolar substance is oil. As water inside and outside of the cell repels the nonpolar tails, they are pushed to the inside of the lipid bilayer (see picture). The polar “heads” however are attracted to water and are therefore located on either side of the bilayer.
Transport proteins are molecules which allow substances to move into or out of the cell, which are unable to move directly through the cell membrane.
The simple model below can be quickly prepared to present the student with information that other students will find in detailed pictures of the cell membrane found in their biology books. This model is accessible to students both tactually and visually.