1.5 Lipids

• What are lipids made of?

  Carbon, hydrogen, and oxygen
• What are the main types of lipids?

  Triglycerides and phospholipids
• What type of bonds join fatty acids to glycerol in triglycerides?

  Ester bonds formed in condensation reactions
• In which solvents are lipids soluble?

  Organic solvents like alcohols
• What are triglycerides composed of?

  One glycerol and three fatty acids
• What effect do double bonds have on lipids?

  They can be saturated or unsaturated
• What are saturated lipids?

  Lipids without carbon-carbon double bonds
• How many different types of fatty acids exist?

  Over 70 different types
• Where are unsaturated lipids commonly found?

  In plants
• What are the properties of triglycerides related to their structure?

  • High energy-storing carbon-hydrogen bonds
  • Low mass to energy ratio
  • Insoluble in water
  • Release water when oxidized
• Why are triglycerides considered excellent energy stores?

  High ratio of energy-storing bonds
• Why are unsaturated fats liquid at room temperature?

  They cannot pack tightly due to bending
• What is the significance of triglycerides' low mass to energy ratio?

  Less mass to move for animals
• How do triglycerides affect the water potential of cells?

  They are insoluble in water
• What do triglycerides provide for organisms in dry environments?

  An important source of water
• What is substituted in phospholipids compared to triglycerides?

  A phosphate-containing group
• What are the characteristics of the phosphate heads and tails in phospholipids?

  Heads are hydrophilic, tails are hydrophobic
• What structure do phospholipids form in water?

  Micelles
• What does the polar nature of phospholipids allow in an aqueous environment?

  Formation of a bilayer
• How do phospholipids contribute to the cell surface membrane?

  Hydrophilic heads hold at the surface
• What do phospholipids form with carbohydrates?

  Glycolipids for cell recognition
• What is the procedure for the emulsion test for lipids?

  1. Use a grease-free test tube
  2. Add 2cm³ sample and 5cm³ ethanol
  3. Shake to dissolve lipid
  4. Add 5cm³ water and shake gently
  5. Cloudy-white indicates lipid presence
  6. Control: use water as sample
• What indicates the presence of lipids in the emulsion test?

  A cloudy-white color
• What should happen in the control of the emulsion test?

  The solution should remain clear
• What are lipids made of?

  Carbon, hydrogen, and oxygen
• In which solvents are lipids soluble?

  Organic solvents like alcohols
• What are the main types of lipids?

  Triglycerides and phospholipids
• What are triglycerides composed of?

  One glycerol and three fatty acids
• What type of bonds join fatty acids to glycerol in triglycerides?

  Ester bonds formed in condensation reactions
• How many different types of fatty acids exist?

  Over 70 different types
• How do double bonds affect the classification of lipids?

  They determine if lipids are saturated or unsaturated
• What characterizes saturated lipids?

  No carbon-carbon double bonds
• Where are unsaturated lipids commonly found?

  In plants
• Why are unsaturated fats liquid at room temperature?

  They cannot pack tightly due to bending
• What are the properties of triglycerides related to their structure?

  • High energy-storing carbon-hydrogen bonds
  • Low mass to energy ratio
  • Insoluble in water
  • Release water when oxidized
• Why are triglycerides considered excellent energy stores?

  High ratio of energy-storing bonds
• What is the significance of triglycerides' low mass to energy ratio?

  Less mass to move for animals
• How do triglycerides affect the water potential of cells?

  They are insoluble in water
• What do triglycerides provide for organisms in dry environments?

  An important source of water
• What is substituted in phospholipids compared to triglycerides?

  A fatty acid is replaced by a phosphate group