2. Lipids

• Lipids


  A group of hydrophobic biomolecules that play important roles in living organisms
• Lipids


  • Their primary function is long-term energy storage
  • They are also used for protection, insulation, and lubrication
  • They act as precursors for some hormones
  • They are a key component of cell membranes
• Groups of lipids


  • Triglycerides
  • Phospholipids
  • Steroids
  • Waxes
• Lipids are insoluble in water
• Triglycerides


  • Include the fats and oils
  • Fats are solid at room temperature and used by animals for insulation, protection and long-term energy storage
  • Oils are liquid at room temperature and used by plants for long-term energy storage
• Fatty acids


  Have a chain of carbon and hydrogen atoms, a methyl group at one end, and an acid group at the other end
• Fatty acids


  • Can be either saturated or unsaturated
  • Saturated fatty acids have only single carbon to carbon bonds
  • Unsaturated fatty acids have one to several double bonds
• Animal fats have saturated fatty acids


  They are solid at room temperature
• Vegetable oils have unsaturated fatty acids

  They are liquid at room temperature
• Trans-fats


  • Unsaturated fatty acids where the hydrogen atoms are on opposite sides of the double-bond
  • Formed during the production of processed foods and in partially hydrogenated oils
  • Consumption has been associated with cardiovascular disease
• Triglyceride formation

  3 separate fatty acids bond with a glycerol molecule through dehydration synthesis
• Phospholipids


  • Similar to triglycerides but have a phosphate group rather than a third fatty acid attached to the glycerol
  • The phosphate head is hydrophilic, the fatty acid tails are hydrophobic
  • Arrange themselves so the hydrophilic heads interact with water and the hydrophobic tails crowd inward
  • Major component of plasma membranes
• Steroids


  • Composed of four fused rings of carbon to which different functional groups are attached
  • Cholesterol is a well-known steroid molecule that serves as a precursor for other steroids like testosterone, estrogen, vitamin D, and cortisone
  • Cholesterol stabilizes plasma membranes
• Waxes


  • Non-polar and repel water
  • Found in protective coatings on leaves and on outer surfaces of animals
  • Produced in the ears of some animals to protect the eardrum
  • Bees construct honey combs from wax