Medicine & USMLE


  1. Fatty Acids
  2. Triacylglycerols
  3. Phospholipids
  4. Sphingolipids
  5. Terpenes
  6. Steroids
  7. Waxes


Phospholipids are a class of lipids that contain a glycerol backbone attached to a phosphate head and two fatty acid tails. The fatty acid tails are attached to the glycerol by ester linkages, which can be broken by hydrolysis. The phosphate heads in phospholipids are polar and hydrophilic, while the fatty acid tails are nonpolar and hydrophobic. As a result, phospholipids are amphipathic, which makes them perfect for composing the lipid bilayer of our cell membranes. 

Key Points

  • Phospholipids
    • Structure
      • Backbone: Glycerol
      • Attachments:
        • 2 Fatty Acids
        • Phosphate Group
        • Ester linkages connect fatty acids to glycerol
    • Roles
      • Primary component in cell membranes (lipid bilayer)
    • Amphipathic
      • Hydrophobic FA tails
      • Hydrophilic phosphate head

(From OpenStax, Wikimedia Commons. Available by CC 4.0)