Formation of phospholipids
Consist of a glycerol backbone with 2 fatty acids (hydrophobic in nature) and one phosphate group (hydrophilic in nature) attached to it. See diagram below.
Makes up the plasma membrane of cells.
Fig. 22 Structure of a phospholipid molecule which has water soluble and water-insoluble regions. The two fatty acid molecules make up the water-insoluble regions while the phosphate group makes up the water-soluble region.
Phospholipid bilayer
Make up the plasma membrane of cell.
As both the interior and exterior of a cell are aqueous in nature (ie contain water), the phospholipids molecules arrange themselves in a bilayer as shown in below.
Fig. 23 Arrangement of phospholipid molecules to form a phospholipid bilayer. The two layers of phospholipid molecules are arranged such that the water-soluble phosphate groups face the aqueous exterior environments while the water-insoluble fatty acids face inwards and are shielded by the phosphate heads.
The arrangement is such that the hydrophilic phosphate heads face the aqueous environment both interior and exterior of a cell while the hydrophobic tails face each other on the inside of the cell membrane.
The plasma membrane is fluid because the hydrophobic tails are constantly moving.
The bilayer structure allows the presence of a hydrophobic boundary in an aqueous environment.