1. Lipids
Function
5 classes / types

2. Lipid Function
1. Long-term energy storage (fat)
2. Form cell membrane (phospholipids)
3. Messaging (hormones)
4. Insulation
5. Cushioning of Internal Organs

3. Lipid Function
Why are lipids well suited for long term energy
storage?
 Contain many high energy bonds between
carbon and hydrogen
 Contain twice as much energy per gram than
carbohydrates (very concentrated)
 Thus a much more compact form of storage
than carbohydrate
 Animals store fats in adipose cells

4. Types of Lipid
1. Fat: Triglyceride / triacylglycerol
2. Phospholipid
3. Steroid
4. Wax
5. Carotenoid

5. 1. Fat Structure
Fatty acid
 also known as Glycerol Fatty acid
triglyceride or Fatty acid
triacylglycerol
 Consists of:
 1 glycerol backbone
 3 fatty acid chains

6. Glycerol Structure
Fatty acid
 Basic structure: Glycerol Fatty acid
 3 carbon molecule Fatty acid
 each carbon has a
hydroxyl group
attached
 the alcohols are sites
for condensation
reactions

7. Fatty acid structure
 Basic structure:
 Unbranched chain of carbons
 A carboxyl group at one end
 Fatty acid chains can differ
from each other in two ways:
 Length of carbon chain: 4-24
 Saturation (number of double
bonds)
- Saturated
- Monounsaturated
- polyunsaturated

8. Essential Fatty Acids
The most common fatty acid in living organisms is palmitic acid.
Humans can synthesize and use palmitic acid:
CH3(CH2)14CO2H
or

9. Essential Fatty Acids
Essential fatty acids are those that humans can not
synthesis and must ingest.
Humans can not create double bonds in fatty acids
beyond C10.
1) alpha-Linolenic Acid (an omega-3 fatty acid)

10. Essential Fatty Acids
2) Linoleic Acid (an omega-6 fatty acid)

11. Properties of Fatty acids
Type Saturated Unsaturated
Structure Single bonds Double bonds, kink
State at r.t. Solid liquid
Origin Animals Plants
Examples Butter, lard Olive oil, essential FA
(omega-3/6 fish oil)

12. Property of Saturated Fats
 Saturated fats
are solid!
 Butter sculpture
at the CNE 2012
 Can you guess
who this is?

13. Forming a triacylglycerol
 Condensation
reaction between:
 Hydroxyl on glycerol
 Carboxyl on fatty
acid
 Results in an ester
bond

14. Triacylglycerol model

15. 2. Phospholipid structure
Phosphate
/
Polar
 Glycerol backbone
Glycerol
group Fatty acid
 2 fatty acids chains
Fatty acid
 phosphate/polar group

16. 2. Phospholipid structure
 Polar head: negatively
charged, hydrophilic tail
 Nonpolar tails: fatty
acids, hydrophobic
 Amphipathic: exhibiting
both hydrophilic and
hydrophobic properties

17. Polar Head Groups

18. Polar Head Groups

19. Self-assembly of phospholipid
 Condition: in water (aqueous)
 Self-assembly = spontaneous
aggregate
 Due to hydrophobic interactions
 Micelle: single layer of
phospholipid with polar head
facing out, nonpolar tails facing
inward
http://www.bio.miami.edu/~cmallery/255/255chem/mcb2.20.micelle.jpg

20. Self-assembly of phospholipid
 Phospholipid bilayer have a double layer of
phospholipids where the nonpolar tails
aggregate forming a hydrophobic core
 This is the basic structure of the plasma
membrane
http://www.bio.miami.edu/~cmallery/255/255chem/mcb2.20.micelle.jpg

21. Plasma Membrane
 Membranes are made of a bilayer of
phospholipids.

22. Plasma Membrane

23. Phospholipid Bilayer

24. 3. Steroid
 Carbon skeleton, 4 interconnected rings
 Three 6C rings, one 5C ring
 Common examples:
 cholesterol
 hormones – estrogen, testosterone

25. Steroid
Cholesterol Testosterone
Cortisone Aldoesterone

26. 4. Wax Structure
Long chain hydrocarbons
 Primarily wax esters: a
long chain hydrocarbon
with an ester group
that is not a triglyceride
 Could also involve
alcohol, aldehyde &
ketone groups
http://www.lipidlibrary.co.uk/Lipids/waxes/index.htm

27. Properties of Wax
 Solid at room temperature
 Becomes liquid when melted
 has plastic properties: deforms under
pressure without application of heat
 thermoplastic is a polymer that turns to a
liquid when heated and freezes to a very
glassy state when cooled sufficiently

28. Natural Wax
Natural
 Animal wax: beeswax,
lanolin, shellac
 Vegetable waxes: soy,
jojoba, carnauba
 Mineral waxes: petroleum
(paraffin) from fossil fuels
Synthetic
 Polypropylene,
 Polyethylene

29. 5. Carotenoids
 Natural fat-soluble pigment
 Backbone: 40 carbon molecules with a
polyene chain with alternating single and
double bonds
 terminated by cyclic end-groups

30. Polyene structure

31. Carotenoid: Plant Pigment
 Found in plants, algae, photosynthetic
bacteria
 Pigment needed for photosynthesis in
addition to chlorophyll
 e.g. beta-carotene in carrot
http://i03.i.aliimg.com/img/pb/593/581/248/1273569425304_hz-myalibaba-web15.hst.dsl.en.alidc.net_2444.jpg

32. Carotenoid: use in animals
 Detecting light: e.g. retinal absorbs light in retina
 Serves as antioxidant: double bonds absorb excess
energy from other molecules, protecting cells and
tissues from damaging effects of free radicals
 Source for vitamin A
http://home.caregroup.org/clinical/altmed/interactions/Images/Nutrients/vitAbetac.gif

33. What is common to all lipids?
 The 5 forms of lipids studied are not built
upon any common monomer. What unified
these lipids so that they are all classified
under the ‘lipid’ category?
 In other words, what makes a lipid, a lipid?

34. HW Question
 Why is glycerol not classified as a triose (3C
monosaccharide)?
 Explain how saturation in a fatty acid chain
affects fluidity.
 Explain how the length of the fatty acid chain
affects fluidity.