Lipids

• Lipids


  Also known as “fats” or “triglycerides”

  
• Fatty acids


  Building blocks of lipids

  
• Lipids are organic compounds found in living organisms that are insoluble in water but soluble in nonpolar organic solvents

  
• Functions of lipids


  • Energy source
  • Energy storage
  • Cell membrane structural components
  • Hormones
  • Vitamins
  • Vitamin absorption
  • Protection
  • Insulation

  
• Energy storage: CHO – 4 kcal stored in the liver as Glycogen, Fats – 9 kcal stored in Adipose tissues
• Cell membrane


  Phospholipid bilayer

  
• Fat-soluble vitamins


  • A
  • D
  • E
  • K
• Vitamin K1


  What humans need
• Shock absorber


  Fats serve as a protective layer for vital organs
• Insulation


  Fat stored beneath the skin serves to insulate the body from extremes of cold temperatures
• Classification of lipids based on biochemical function

  • Energy-storage lipids
  • Membrane lipids
  • Emulsification lipids
  • Messenger lipids
  • Protective-coating lipids

  
• Energy-storage lipids


  • Triacyglycerols
  • Most abundant lipid

  
• Membrane lipids


  • Phospholipids
  • Sphingoglycolipids
  • Cholesterol

  
• Emulsification lipids


  • Bile acids

  
• Messenger lipids


  • Steroid hormones
  • Eicosanoids

  
• Protective-coating lipids


  • Biological waxes

  
• Classification of lipids based on saponification

  • Saponifiable lipids
  • Non-saponifiable lipids

  
• Saponifiable lipids


  Converted into smaller molecules upon hydrolysis

  
• Saponifiable lipids examples


  • Triacylglycerols
  • Phospholipids
  • Sphingoglycolipids
  • Biological waxes

  
• Non-saponifiable lipids


  Cannot be broken down into smaller units since they do not react with water

  
• Fatty acids


  Naturally occurring monocarboxylic acids

  
• Fatty acids are rarely found free in nature
• Fatty acid classifications


  • Carbon chain length
  • Saturation

  
• Carbon chain length classifications

  • Long-chain fatty acids (C12 to C26)
  • Medium-chain fatty acids (C8 and C10)
  • Short-chain fatty acids (C4 and C6)

  
• Saturation classifications


  • Saturated fatty acids (SFAs)
  • Monounsaturated fatty acids (MUFAs)
  • Polyunsaturated fatty acids (PUFAs)

  
• Saturated Fatty Acids (SFA)

  All carbon-carbon bonds are single bonds

  
• General formula for SFA

  CH3(CH2)nCOOH
• Higher carbon + longer chain length = higher melting point
• Monounsaturated Fatty Acid (MUFA)


  One carbon-carbon double bond

  
• Configuration of MUFA


  Cis (naturally occurring)
• Polyunsaturated Fatty Acid (PUFA)


  Two or more carbon-carbon double bonds

  
• Up to six double bonds are found in biochemically important PUFAs

  
• Biochemically important fatty acids characteristics

  • An unbranched carbon chain
  • An even number of carbon atoms
  • Double bonds in a cis configuration

  
• Nomenclature of fatty acids

  Two numbers separated by a colon to specify the number of carbon atoms and number of carbon-carbon double bonds

  
• Examples of fatty acid nomenclature

  • 18:0
  • 18:1
  • 18:2

  
• Double-bond positioning notation


  Greek capital letter delta (Δ) followed by one or more superscript numbers
• Arachidonic acid (Omega-6 FA) is a precursor in the synthesis of prostaglandins and leukotrienes

  
• Omega-3 Fatty Acid


  Unsaturated; its endmost double bond three carbon atoms away from its methyl end

  
• Omega-3 fatty acids are precursors of prostaglandins that exhibit anti-inflammatory effects

  
• The American Heart Association recommended that we include at least 2 servings of “oily” fish each week