1. Lipids
Function
5 Types
© The Law of Science

2. Lipid Function
Lipids are most commonly referred to as fat, which is slightly inaccurate as you will learn
Brainstorm: What use do lipids have?

3. Lipid Function Long-term energy storage
Photos are example of sources of good fats

4. 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

5. Lipid Function Membrane of cells, organelles etc. (phospholipid)

6. Lipid Function Insulation

7. Lipid Function Cushioning internal organs

8. Lipid Function
Precursor for several sterol hormones
Examples: fat-soluble hormones and hormones responsible for fat metabolism

9. Lipid Function Summary
Long-term energy storage (fat)
Form cell membrane (phospholipids)
Insulation
Cushioning of Internal Organs
Messaging (hormones)

10. Types of Lipid Fat: Triglyceride / triacylglycerol Phospholipid
Steroid
Wax

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

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

13. 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

14. 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)

15. Property of Saturated Fats
are solid at room temperature
Ex. Butter and lard

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

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

18. 2. Phospholipid structure
Polar head: negatively charged, hydrophilic
Nonpolar tails: fatty acids, hydrophobic
tail

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
Fig. 5.13

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

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

22. Phospholipid Bilayer

23. 3. Steroid Carbon skeleton, 4 interconnected rings Common examples:
Cholesterol – a precursor for making steroid hormones such as estrogen and testosterone and vitamin D
Good and bad cholesterol. Bad = Low Density Lipoprotein. Good = High Density Liopoprotein

24. Steroid
Cholesterol
Testosterone
Cortisone
Aldoesterone

25. 4. Wax
Consists of a long fatty acid chain joined to a long alcohol chain. Waxes are highly waterproof.
In plants and animals they provide protective coatings such as on the cuticle of a leaf.
Earwax prevents micro-organisms from entering the middle ear.

26. Properties of Wax Solid at room temperature Becomes liquid when melted
has plastic properties: deforms under pressure without application of heat

27. Natural Wax Natural Animal wax: beeswax, lanolin, shellac
Vegetable waxes: soy, jojoba, carnauba
Mineral waxes: petroleum
(paraffin) from fossil fuels

28. What is common to all lipids?
The 4 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?