Lipids

• Elements

  Carbon

  Hydrogen

  Oxygen
• Basic Structure

  Triglyceride

  (One glycerol and 3 fatty acids)

  
• Classification

  1. Saturated

  2. Monounsaturated

  3. Polyunsaturated
• Saturated fatty acids

  Full of hydrogen and no double bonds
• What is at the beginning of the fatty acid structures

  Carboxyl group (COOH)

  
• examples of saturated fatty acids

  -Butyric acid

  -Stearic in meat
• Monounsaturated fatty acids

  Carbon atoms are not full of hydrogens- one double bond between the carbon atoms.
• example of a monounsaturated fatty acids

  -oleic acid - olive oil
• Polyunsaturated fatty acids

  Carbon atoms are not full of hydrogens- more than one double bond between the carbon atoms.
• examples of polyunsaturated fatty acid

  Generally found in plant or marine sources e.g...

  -Linoleic acid in nuts

  -Linoleic acid in seeds

  -Arachidonic acid in oily fish
• Cis fatty acids

  Hydrogen atoms are on the same side of the double bond (either above or below)
• Sources of cis fatty acids

  Naturally occurring in foods such as olive oil and oily fish
• Health effects of cis fatty acids

  Raise HDL (high density lipoprotein) and lower levels of LDL (low density lipoprotein) which is good for health
• Trans fatty acids

  Hydrogen atoms are on opposite sides of the double bond
• Sources of trans fatty acids

  -Formed from cis fatty acids during the heating or frying of oils at a high temperature

  -Also present in foods that contain hydrogenated fats
• Health effects of trans fatty acids

  lower HDL and increase LDL which increases risk of coronary heart disease
• Essential fatty acids

  Fatty acids that cannot be made by the body, so must be gotten from food sources
• Functions of EfAs

  Cell membrane formation

  Reduce risk of CHD (Coronary heart disease)
• Omega-3 fatty acids

  Have a double bond between the third and fourth carbon atoms along their hydrocarbon chain
• Sources of Omega-3

  Flaxseed oil

  Walnuts

  Fish oils e.g. Cod liver oil
• Functions of Omega-3

  Reduce the risk of coronary heart disease and strokes

  Aids foetal brain development
• 1. Solubility

  Lipids are insoluble in water, but soluble in other liquids such as ether and benzene
• 2. Absorption of flavours

  Lipids absorb flavours easily e.g chili infused oils/ garlic butter
• 4. Emulsions

  An emulsion is a solution formed when to immiscible liquids are forced to mix together.

  
  

  Two types: Water in oil emulsions or Oil in water emulsions
• 5. Hydrogenation

  A process whereby hydrogen gas is forced through the double bond of an unsaturated oil, converting the unsaturated oil into a solid, saturated fat.
• Biological functions of lipids

  -Supply body with heat and energy

  -Protect delicate organs

  -Supply body with fat soluble vitamins

  -Excess lipids are stored as adipose tissue under the skin
• Stomach

  Heat within stomach causes the fat to melt
• Liver- secretes bile which


  emulsifies large fat molecules to produce smaller molecules
• Pancreas- secretes pancreatic juice which


  Secretes pancreatic juice into the small intestine which contains enzyme lipase. Breaks lipids into fatty acids and glycerol
• Small intestine secrete intestinal juice which


  contains lipase and continues the breaking down of the lipids into their basic form
• Absorption of lipids

  the fatty acids and glycerol pass through wall of villi into lacteals, which forms part of the lymphatic system
• After it is absorbed through the villi it travels to

  the bloodstream through the subclavian vein
• Excess digested lipids

  Stored as adipose tissue under the skin to insulate body and act as an energy reserve
• What is at the beginning of the fatty acid structures

  Methyl group (CH3)
• Heating lipids- Melting point

  Solid fats melt when heated to 30-40 degrees celsius
• Heating lipids: smoke point

  If lipids are heated to 200 degrees they begin to decompose, cause the glycerol to separate from the fatty acids. Glycerol is then broken down to acrolein and produces blue smoke and an acrid smell.
• Heating lipids-Flash point

  Extreme overheating of lipids to 310 degrees causes a vapour to be emitted that can spontaneously ignite
• Rancidity (Spoilage of fats) Hydrolytic rancidity

  When enzymes or bacteria break down lipids into glycerol and fatty acids
• Rancidity (Spoilage of fats) Oxidative rancidity

  When oxygen in the air combines with the carbons in a double bond of an unsaturated fat.