2.1 Structure and Classification of Lipids

• Lipid

  • An organic compound found in living organisms that is insoluble (or only sparingly soluble) in water but soluble in non-polar organic solvents.
  • Unlike other biomolecules, they do not have a common structural feature that serves as the basis for defining such compounds.
• 2 methods of Lipid classification:

  • Biochemical function
  • Saponification
• Classification based on Biochemical functions:

  • Energy-storage lipids (triacylglycerols)
  • Membrane lipids (phospholipids, sphingoglycolipids, and cholesterol)
  • Emulsification lipids (bile acids)
  • Messenger lipids (steroid hormones and eicosanoids)
  • Protective - coating lipids (biological waxes)
• Classification based on Saponification

  • Saponifiable lipids (triaclyglycerols, phospholipids, sphingoglycolipids, cholesterol, and biological waxes)
  • Nonsaponifiable lipids (bile acids, steroid hormones, and eicosanoids)
• Saponification reaction

  • A hydrolysis reaction that occurs in a basic solution (Ph above 7)
• • Lipids exhibit structural diversity
  • Some are esters, some are amides, and some are alcohols (acyclic, cyclic, and polycyclic).