Fluid mosaic model

• The plasma membrane is made of a bilayer of phospholipid molecules that act as a barrier. The hydrophilic head of the phospholipids lie at the surface of the bilayer and the hydrophobic tails group together in the interior. The bilayer prevents the passage of water-soluble molecules.
• Proteins are also found embedded within the cell membrane. They may be hydrophilic with polar groups or hydrophobic with nonpolar side groups.
• Another lipid found in the plasma membrane of eukaryotic cells is cholesterol which is responsible for the fluidity of the membrane.
• An oligosaccharide is attached to some of the proteins and lipids forming glycoproteins and glycolipids respectively. They can flow around the surface of the cell within the membrane.