Lipids

• What are the characteristics of lipids?

  • Insoluble in water
  • Soluble in solvents like alcohol
• What do lipids do?

  • Component in cell membranes
  • Insulation
  • Protection
• What is the structure of a triglyceride?

  3 fatty acids combined with glycerol via an ester bond in a condensation reaction
• What are the properties of triglycerides?

  • Low mass to energy ratio
  • Large and non-polar, so can’t diffuse out of cells
• What is the structure of a phospholipid?

  2 fatty acids, a glycerol and a phosphate

  • Hydrophilic head - interacts with water not with fat
  • Hydrophobic tail - interacts with fat but not water
• What are the properties of phospholipids?

  • Polar so make a hydrophobic barrier
  • Help form glycoproteins within the cell membrane
• What is the test for lipids?

  The emulsion test

  • Add the sample to a test tube with ethanol
  • Shake tube to dissolve lipid
  • Add water and shake
  • If positive a milky white emulsion occurs