Lipids

• What do lipids include?

  Fats and oils
• Basic properties of lipids?

  Made from C,H,O only

  Non-polar molecules and insoluble in water

  At room temp saturates fats are solids, unsaturated are liquids.
• What defines a saturated fat?

  No double bonds, and not liquid at room temp
• What defines an unsaturated fat?

  Contains double bonds, causing the molecule to bend, meaning it cannot fold together closely. It is a liquid at room temp.
• What is a triglyceride made up of?

  Glycerol and 3 fatty acids
• What is a phospholipid made from?

  1 glycerol, 2 fatty acids and 1 phosphate molecule
• What are the functions of lipids?

  Heat insulation

  Shock absorption

  Buoyancy

  Cell Membranes

  Waterproofing
• How are triglycerides and Phospholipids formed?

  Via a condensation reaction, ester bonds form.
• What is the function of a phospholipid?

  Hydrophilic head and hydrophobic tail allows them to act as a cell membrane. Knowns as a phospholipid bilayer to maintain structure.
• What are triglycerides and phospholipids soluble in?

  Organic solvents
• How does the function and properties of a lipid change?

  Depends on the fatty acid hydrocarbon chain.
• How do fatty acid tails change?

  Length and saturation
• Digestion of Lipids:

  1. Lipase catalyses the hydrolysis the ester bonds of lipids, broken into monoglycerides and fatty acids.
  2. Lipases made in the pancreas and work in the small intestine
• How are lipids digested?

  1. Emulsified by bile salts into micelles

  2. Micelles are digested in the epithelial cells of the small intestine

  3. Releases monoglycerides and fatty acids

  4. Non polar so can pass directly though the cell surface membrane and into the epithelial cells

  5. SER synthesises the fatty acids and monoglycerides into triglycerides

  6. These associate with cholesterol and lipoproteins to form chylomicrons

  7. Chylomicrons move out of the cell by exocytosis

  8. Enter lymphatic capillaries called lacteals and then pass into the blood stream where the triglycerides are hydrolysed and diffuse into the cells
• How do you test for lipids?

  Add ice cold ethanol to sample and shake so it dissolves.

  Add the dissolved sample into pure water, in which it is insoluble.

  White, cloudy emulsion forms.