4.2 Phospholipids

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. 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.