1. Fats and Oils (lipids) Look at the chemical structure of lipids
Know the difference between saturated and unsaturated fats
Understand the difference between cis and trans isomers
Understand how trans-fats are made
Consider health issues around fat consumption.
Saponification

2. Sources of fats and oils in our diets

3. What are lipids
They are esters of fatty acids and glycerol. Three fatty acids are combined to one glycerol to make what is known as a triglyceride.
Glycerol is a triol (an alcohol made with three hydroxyl groups
Fatty acids are long chain carboxylic acids

4. Digestion
In the digestive system enzymes hydrate (add water) to break the bonds and create a triol: glycerol and three fatty acids

5. Some chemistry of common fatty acids
Name
Carbon atoms
Double bonds
Melting point (C)
Source
Lauric acid 12 43
Coconut
Myristic acid 14 54
Nutmeg
Palmitic acid 16 62
Palm oil
Stearic acid 18 69
Animal Fat
Palmitoleic acid 1
Butter
Oleic acid 13
Olives and corn
Linoleic acid
Linolenic acid 2 3 -9
-17
Soybean, safflower, sunflower
Corn
What patterns do you observe?

6. Saturated and unsaturated fatty acids
What is the difference?

7. Write their condensed structural formulae

8. Dietary advice Saturated fats pack together more tightly.
Therefore they have higher melting points
This makes them more likely to deposit in your circulatory system
Animal fats contain more saturated fats
Plant fats contain more unsaturated fats
Hence plant fats are healthier

9. Dietary advice
Which would you expect to be the most/least healthy fats here?

10. Omega 3 and omega 6 acids These are considered healthy
Low risk of disease of circulatory system
Unsaturated fats
Common in oily fish
Omega 6 1st double bond links carbon 6 – 7
Omega 3 1st double bond links carbon 3 – 4

11. Health benefits of omega 3 fatty acids
Noticed in Inuit
High fish diet (salmon, char etc. oily fish)
Very high blood cholesterol levels due to high meat diet
Low levels of cardiovascular disease
Omega 3 make blood platelets less sticky
Blood does not get stuck where deposits of plaque have narrowed blood vessels
Doesn’t form clots leading to strokes or heart attacks.
Too much and you may have difficulty stopping bleeding.

12. Cis and trans What is the difference?
These relate to the unsaturated bonds in fatty acids
What is the difference?

13. Cis and trans fats Cis bonds make fatty acid chains bend
Trans fats produced by hydrogenation of unsaturated fatty acids
Trans fats normally man made
Naturally occurring fatty acids normally cis
This affects their properties
Trans bonds make fatty acid chains long and straight.
Cis bonds make fatty acid chains bend

14. Why are cis better for you.
Cis are kinked so shorter
Have less surface area in contact between molecules so melt at lower temps
What does this remind us of?
Therefore remain liquid in body
Therefore easier to move away from blood vessels
Being more curled up are higher density
This is why high density cholesterol is better than low density cholesterol.

15. In view of this, why do we hydrogenate unsaturated fats
The aim is to turn liquids into soft solids such as spreadable butters and margarines etc.
These soft solids have many more industrial food uses
As we hydrogenate unsaturated fats double bonds are converted to single bonds

16. Hydrogenation continued
This process is not fully completed because completely hydrogenated fats are very brittle and of no use.
Seen as beneficial as the end products from hydrogenated vegetable oils do not contain cholesterol like animal fats would, but have similar useful physical properties

17. Creating Trans fats Hydrogenation converts some cis to trans bonds
Partially or fully hydrogenated fats in foods will contain trans fats
Trans fats have long chains like saturated fatty acids and behave like saturated fatty acids
Studies suggest high intake of trans fats lowers levels of good HDL-cholesterol.
Thus linked to increased risk of heart disease.

19. Saponification Soap is made from fatty acids or triglycerides
These are heated with a strong base such as sodium hydroxide
NaOH makes solid soaps
KOH makes more liquid soaps
Fat/oil + strong base = glycerol + fatty acid salt
Tripalmitin + NaOH = glycerol + sodium palmitate

20. Plenary questions 1. All fats are made up of what?
2. Why are they called triglycerides?
3. Fats are a complex type of which organic chemical
4. What is meant by cis and trans isomers?
5. How do cis and trans bonds affect the structure of fats?
6. What a re polyunsaturated fats?
7. What features do they have that is thought to make them less harmful?
8. What observation brought to light the value of omega 3?