To basically demonstrate the importance of lipids, let's focus in this lecture on this cell membrane. So the cell membrane is a structure that encloses every single cell inside our body and it consists predominantly of lipids. Now, what exactly are some functions of the cell membrane? Well, the cell membrane has four important functions. Function number one is it creates a protective barrier between the outside and the inside environment of the cell. It basically prevents toxins and other pathogenic agents from actually entering the cell and it prevents molecules from actually spontaneously exiting the cell in the first place.