Each phospholipid molecule in a cell membrane consists of

In early 1972, Singer and Nicolson proposed fluid mosaic model for the membrane structure. As per the model, the cell membrane consists of a highly viscous, fluid matrix of 2 layers of phospholipid molecules, having globular proteins associated with them. The lipids and proteins  vary from one type of membrane to another. The phospholipid molecules are amphipathic, i.e., have both hydrophilic and hydrophobic regions. Each phospholipid molecule like lecithin has one polar, hydrophilic head directed outward and two non-polar, hydrophobic tails (fatty acid) pointing inwards.