lipids

• Biochemical test for lipids

  1) Crush sample

  2) Add ethanol and shake

  3) Then add water

  4) A white emulsion forms of lipids are present
• What are the two groups of lipids?

  Triglycerides Phospholipids
• What are the roles of lipids in the body?

  Phospholipids = Important component of cell membranes

  Triglycerides = Energy storage, found in food
• How are triglycerides formed?

  Condensation of one molecule of glycerol and three fatty acid molecules

  
  

  NOT A POLYMER AS IT ISN'T MADE OF THE SAME MONOMERS
• How is an ester bond formed?


  A condensation reaction between glycerol and a fatty acid (RCOOH)
• What elements do all lipids contain?

  Carbon

  Hydrogen

  Oxygen
• What are fatty acids?

  Consist of a hydrocarbon chain and a carboxylic acid group.

  The hydrocarbon chains vary in length and can be referred to as 'R' (whole fatty acid = RCOOH)
• What is the 'R' group?


  Variable hydrocarbon chain
• What is a saturated fatty acid?


  Single bond between carbon atoms in the hydrocarbon chain
• What is an unsaturated fatty acid?


  Double bond between the carbon atoms in the hydrocarbon chain
• Describe the difference between the structure of a triglyceride and a phospholipid

  A triglyceride has 3 fatty acids attached to the glycerol whereas in a phospholipid one fatty acid is replaced by a phosphate
• What do triglycerides do in water?

  Clump together

  Fatty acid tails face onwards to shield themselves from water with their glycerol heads

  Forming insoluble droplets
• Triglycerides - structure

  The fatty acid tails are hydrophobic (repel water) making them insoluble in water
• Phospholipids - structure

  Phosphate group has a negative charge (polar) whereas the fatty acid tails don't have a charge (non polar)

  
  

  Phosphate head = hydrophilic (attracts water) - water soluble

  Fatty acid tails = hydrophobic (repel water)

  
  

  Allowing them to form a bilayer in water
• Describe and explain how phospholipids are arranged in a cell membrane

  - Phospholipids are arranged in a bilayer

  - The phosphate heads face the outside and inside of the cell so that they are in contact with water because they are hydrophilic

  - The fatty acid tails are in the middle of the membrane away from the water because they are hydrophobic