Lipids

• Lipids


  A diverse group of organic molecules that are insoluble in water but soluble in nonpolar solvents, including fats, oils, waxes, phospholipids, and steroids

  
• Lipids


  • Insoluble in water but soluble in nonpolar solvents
  • Serving as a concentrated source of energy
  • Playing a role in cell membrane structure
  • Hormone production
  • Insulation
  • Providing a long-term energy reserve for the body

  
• Functions of lipids


  • Energy storage
  • Structural components
  • Hormone production
  • Insulation

  
• Classification of lipids based on biological functions


  • Storage lipids (e.g. triglycerides)
  • Structural lipids (e.g. phospholipids, cholesterol)

  
• Classification of lipids based on chemical composition

  • Simple lipids
  • Compound or complex lipids
  • Derived lipids
  • Miscellaneous lipids

  
• Triacylglycerol (Triglyceride)


  An ester of glycerol with three fatty acids, also called neutral fat
• Triacylglycerol


  • Stored in adipocytes in animals, endosperm and cotyledon cells in plants
  • Mammal contains 5% to 25% or more of its body weight as lipids, 90% triacylglycerol
• Saturated fatty acids have single bonds, unsaturated fatty acids have double bonds, hydroxy fatty acids have hydroxyl groups, and cyclic fatty acids have ring structures
• Lipoproteins


  Made up of some lipids combined with some specific proteins, soluble in water because of their protein content

  
• Lipids in lipoproteins


  • Triglycerides
  • Phospholipids
  • Cholesterol
  • Fatty acids

  
• Chemical reactions of lipids

  • Hydrolysis
  • Saponification
  • Hydrogenation
  • Iodination

  
• Iodine absorption value


  Used to determine the amount of unsaturation in fats, oils and waxes
• Steroids


  Lipids containing a steroid nucleus (core structure)
• Major classes of steroid hormones

  • Testosterone (androgen)
  • Estradiol (estrogen)
  • Progesterone (progestin)
  • Cortisol/corticosterone (glucocorticoid)
  • Aldosterone (mineralocorticoid)