Phospholipid bilayer membrane

 The phospholipid bilayer is composed of 2 layers. Phospholipids form the bilyar and they are constructed from two hydrophobic tails "water-fearing" and a hydrophilic head "water-loving" which is polar. These are the most common membrane lipids found in the phospholipid bilayer membrane. This amphiphillic nature of the phospholipids cause them to form billayers in water. In water, the hydrophillic heads will dissolve as the charged or uncharged polar heads can form hydrogen bonds or electrostatic interactions. Hydrophobic tails will not dissolve in water as their tails are non polar and cannot form these bonds. ¹

1) Alberts et al. (2008), Molecular Biology of the Cell, 5th Edition, New York: Garland Science, Taylor & Francis Group.