Lipids

• What are lipids essential for in cells?

  Cell membranes
• What percentage of your body is made up of lipids?

  23%
• What is a triglyceride composed of?

  One glycerol and three fatty acids
• How are triglycerides formed?

  By a condensation reaction
• Why are lipids hydrophobic?

  They have long hydrocarbon tails
• What do fatty acids consist of?

  A hydrocarbon tail and a carboxyl group
• What is the difference between saturated and unsaturated fatty acids?

  Saturated have no double bonds; unsaturated do
• What are the key features of phospholipids?

  • Similar to triglycerides
  • One fatty acid replaced by a phosphate group
  • Hydrophilic phosphate group and hydrophobic tails
  • Form bilayers in cell membranes
• What is the role of triglycerides in the body?

  Energy storage molecules
• Why do triglycerides contain more energy than carbohydrates?

  Long hydrocarbon tails contain lots of chemical energy
• How do triglycerides affect water potential in cells?

  They are insoluble, preventing water influx
• What happens to the fatty acid tails in triglycerides?

  They face inwards, shielding from water
• What is the structure of a phospholipid in a cell membrane?

  Heads face water; tails face inward
• What is the function of the phospholipid bilayer?

  Controls what enters and leaves a cell
• What is the emulsion test used for?

  To test for lipids in a sample
• What indicates the presence of lipids in the emulsion test?

  A milky emulsion forms
• How does the amount of lipid affect the emulsion test result?

  More lipid results in a more noticeable color
• What type of bond is formed between glycerol and fatty acids?

  An ester bond
• What is the difference between a saturated and unsaturated fatty acid in terms of structure?

  Saturated has no double bonds; unsaturated has at least one
• How do the structures of triglycerides and phospholipids relate to their functions?


  Triglycerides:

  • Energy storage
  • Long hydrocarbon tails provide energy
  • Insoluble, affecting water potential

  
  

  Phospholipids:

  • Form cell membrane bilayer
  • Hydrophilic heads and hydrophobic tails
  • Control substance passage in and out of cells