Lipids

• What are fats also known as?

  Lipids and triglycerides
• What elements do lipids contain?

  Carbon, hydrogen, and oxygen
• How do the hydrogen and oxygen ratios in lipids compare to carbohydrates?

  They contain more hydrogen than oxygen compared to carbohydrates
• What are the properties of lipids?

  • Store twice as much energy as carbohydrates
  • Insoluble in water
  • Soluble in alcohol (ethanol used in food tests)
  • Can be solid (fat) or liquid at room temperature
• What are the main functions of lipids?

  Store energy, provide insulation, protect organs, and allow for buoyancy
• What is the general formula for fatty acids?

  1. COOH
• What is formed when glycerol combines with three fatty acids?

  Triglyceride and three water molecules
• What is a monoglyceride?

  One fatty acid attached to glycerol
• What is a diglyceride?

  Two fatty acids attached to glycerol
• What characterizes saturated fatty acids?

  They have only single C-C bonds in the R group
• What characterizes unsaturated fatty acids?

  They contain double C=C bonds in the R group
• How is a lipid molecule formed?

  • Glycerol combines with three fatty acids
  • Ester bonds are formed
  • Water molecules are removed in condensation reactions
• Are lipids considered polymers?

  No, because they are made up of two components (glycerol and fatty acids)
• What is the test for lipid emulsion?

  1. Add ethanol to the sample (lipids dissolve in ethanol)
  2. Add water (lipids are insoluble in water)
  3. Shake the mixture

  • Clear solution indicates lipids present: milky white emulsion
• What is the structure of phospholipids in cell membranes?

  They form a bilayer with hydrophobic tails facing inward and hydrophilic heads facing outward
• What happens when phospholipids come in contact with water?

  A single layer is formed with hydrophobic heads attracted to water and hydrophobic tails repelling it
• What are the characteristics of phospholipid tails and heads?

  • Tails: Non-polar, hydrophobic, repel water
  • Heads: Polar, hydrophilic, attracted to water
• How do phospholipids arrange themselves in the cell membrane?

  • Fatty acid tails positioned away from water
  • Phospholipid heads positioned towards water
  • Forms a bilayer structure