Midterms 1

• Five functions of lipids

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


  Lipids stored for use when energy demand is high<|>Triacylglycerols are the stored form of energy
• Energy-storage lipids


  • Triacylglycerols are concentrated primarily in special cells (stored in fat cells known as adipocytes)
• Fats


  Predominantly saturated, solids or semisolids at room temperature (25 C)
• Oils


  Predominantly unsaturated, liquids at room temperature
• Membrane lipids


  Lipids that are structural components of cell membranes
• Membrane lipids

  • Has 3 major membrane lipids: Phospholipids, Cholesterol, Sphingoglycolipids
• Cholesterol


  C27 steroid molecule, important in human cell membranes, nerve tissue and brain tissue, a constituent of animal cells
• Sphingoglycolipids


  Contains both a fatty acid and carbohydrate, simple sphingoglycolipids are called cerebrosides, complex sphingoglycolipids are called gangliosides
• Emulsification lipids


  Lipids that stabilize and disperse water-insoluble materials in aqueous solution
• Bile acids


  Tri- or dihydroxy cholesterol derivatives, produced in the liver, stored in the gallbladder, and released into the small intestine during digestion
• Messenger lipids


  Regulatory lipids that act in the tissue where they are synthesized or at other locations after transport via the bloodstream
• Types of messenger lipids

  • Steroid hormones
  • Eicosanoids
• Steroid hormones

  Biochemical substances produced by ductless glands that have a messenger function, derivatives of cholesterol
• Types of steroid hormones

  • Sex hormones (estrogens, androgens, progestins)
  • Adrenocorticoid hormones (mineralocorticoids, glucocorticoids)
• Eicosanoids


  C20-fatty-acid derivatives containing cyclic or linear structures, including prostaglandins, thromboxanes, and leukotrienes
• Protective-coating lipids

  Water-insoluble, water-repellant lipids with protective-coating and lubricant functions
• Biological waxes


  Acts as a thermal-insulator that can be found in the subcutaneous tissues and around certain organs, protect hair and skin, keep it pliable and lubricated, impart water repellency to animal fur, protect plant leaves from excessive evaporation and parasite attack
• Saponification


  A hydrolysis reaction carried out in a basic solution or alkali solution (NaOH and KOH)
• Saponifiable lipids


  Lipids that undergo the process of saponification, have fatty acids
• Nonsaponifiable lipids


  Lipids that have only one fatty acid, no site for linkages
• Water solubility of lipids

  Directly function of the carbon chain length, solubility decreases as the carbon chain increases, shorter chain of carbon atoms are slightly soluble in water
• Melting point of lipids


  Influenced by the carbon chain length and the degree of unsaturation (presence or number of double bonds)
• Saturated fatty acids

  Have no double bonds
• Unsaturated fatty acids


  Contain double bonds, can be monounsaturated (1 double bond) or polyunsaturated (more than 1 double bond)
• As the carbon chain increases, the higher the temperature needed for it to melt, hence the melting point also increases
• The more double bonds present, the less efficient in packing
• Structural notation for fatty acids

  No. of Carbon: No. of Double Bonds, Delta Classification (placement of double bonds), Omega Classification (location of first double bond from methyl end)