In Eukaryotes the cell membrane is explained as Fluid Mosaic Model by Schleiden and Schwann. According to this model the plasma membrane is made up of Lipids and Proteins. The lipids are arranged in a bilayer. The lipids present are phospholipids. These are arranged in such a way that the polar heads are towards the outer side and hydrophobic ends are towards the inner side. The ratio of proteins and lipids are different in different cell types. In humans it is seen that around 40 percent is lipid and 52 percent is protein. This was explained as Fluid Mosaic model. This explains that the quasi- fluid nature of lipid causes the movement of proteins throughout the bilayer structure. This is termed as fluidity.