Educator

Cell Membranes

• Cell membranes are surprisingly dynamic structures. The diverse functions of a cell's membrane make the membrane as dynamic as the cell's interior.

• Contrary to the earliest assumptions about cell membrane structure, we now know that the cell membrane must be more than just a fortress to protect the inside of the cell from the outside. It must contain biological doors, windows, gates, and drawbridges — intricate structures that function together to give the membrane a selectively permeable nature.

• The health and vitality of the cell depend on the ability of the cell membrane to keep certain substances out while allowing the free passage of others.

• Earlier in this unit, we learned that cells are surrounded by plasma membranes composed of a double layer, or bilayer, of phospholipid molecules oriented with their polar groups to the outside. But since a membrane has to perform a wide range of functions, there's a lot more to its structure than a simple phospholipid bilayer!