membrane lipid

Last reviewed 01/2018

The plasma membrane lipid is divided into three groups arranged in a bilayer:

  • phospholipids:
    • polar head group:
      • site of phosphate residue
      • it is hydrophilic and sits on outside of bilayer
      • joined to 2 long chain fatty acids via glycerol
    • fatty acids:
    • 14-24 carbon atoms long
      • hydrophobic
      • sit on inside of membrane
    • five key types:
    • phosphatidylcholine; mainly in outer bilayer; used in arachidonic acid metabolism
      • phosphatidylinositol; used in arachidonic acid metabolism
      • sphingomyelin; mainly in outer bilayer
      • phosphatidylserine; mainly in inner bilayer
      • phosphatidylethanolamine; mainly in inner bilayer
  • cholesterol:
    • hydroxyl head sits on outside of bilayer
    • steroid core interacts with hydrophobic interior of membrane
    • increases strength and decreases fluidity of bilayer
  • glycolipids:
    • present on outside of bilayer leading to term 'cell coat'
    • also termed the glycocalyx
    • may act as immune recognition molecules and receptors for transmitters