1. Lipids and Fats

2. Why do we need fat?

3. Hibernating animals,Migrating birds Hormone cell membranes Bile acid
Protection
Vitamin
Saturated fatty acids
Unsaturated fatty acids
Essential FAs
Triacylglycerol
Phospolipid
Sphingolipid
Sphingomyelin
Lecithin
Liposome

4. Fats
(Triglyceride or triacylglycerole)
To store and supply energy
Lipids
Phospholipids
To be important membrane components
Glycolipids
Lipoids
Cholesterol
Cholesterol ester

5. 1. Major portion of a lipid is hydrophobic due to
I. Defining features of lipids
1. Major portion of a lipid is hydrophobic due to
many (aliphatic) CH2 groups.
2. Minor portion is hydrophilic, allows interaction with
the aqueous environment.
3. Do not exist as large polymers (unlike nucleic
acids, proteins and polysaccharides).
hydrophobic
hydrophilic

6. II. Major functions of various lipid classes
1. Energy storage: fats (animals) & oils (plants)
2. Membranes: glycerophospholipids, sphingolipids,
cholesterol & others in the famous lipid bilayer.
3. Specialized roles:
Hormones (e.g., corticosterone)
Vitamins (e.g., vitamin E)
Signaling molecules (e.g., diacylglycerol)

7. II-1 Storage lipids: fats & oils
1. Triacylglycerols = triglycerides = fats O
H2C-O-C-CH2-/\/\/\/\/\/\/\-CH3
 HC-O-C-CH2-/\/\/\/\/\/\/\-CH3
glycerol is acylated to form an ester of a fatty acid O
glycerol O
fatty acid

8. H2C-O-C-CH2-/\/\/\/\/\/\/\-CH3 HC-O-C-CH2-/\/\/\/\/\/\/\-CH3
Saponification of triglycerides
NaOH, water, heat
Saponification value
Soap
H2C-OH
HC-OH
glycerol
O-C-CH2-/\/\/\/\/\/\/\-CH3 O -
free fatty acid (as a soap)
(Na+ vs Mg++ or Ca++)

9. II-1 Storage lipids: fats & oils
2. Fatty acids (FAs)
Free fatty acids in blood are mostly bound to serum albumin, an abundant blood protein.
Nomenclature and size of Fats.
HO-C-CH2-(CH2)13-CH3 O
(1) palmitic acid:
A saturated fatty acid
16:0
（2）stearic acid

10. (4) linoleic acid: an unsaturated fatty acid
18:2c9,12 (c=cis)
HO-C-(CH2)7-CH=CH-CH2-CH=CH-(CH2)4-CH3 O

11. Classification of fatty acids
Numerical Symbol
Common Name
Comments
14:0
Myristic acid
Saturated
16:0
Palmitic acid
18:0
Stearic acid
 Saturated
16:1 Δ 9
Palmitoleic acid
Unsaturated
18:1 Δ 9
Oleic acid
18:2 Δ 9,12
Linoleic acid
EFA
18:3 Δ 9,12,15
Linolenic acid
20:4 Δ 5,8,11,14
Arachidonic acid

12. Essential Fatty Acids (EFA)
Linoleic, linolenic and arachidonic acids are called essential fatty acids, because they cannot be synthesized by the body and must be obtained through diet.

13. H2C-O-C-CH2-/\/\/\/\-CH3 HC-O-C-CH2-/\/\/\/\/-CH3 -CH2 O
R-O-P-O -
II.3 Membrane lipids: 1. Glycerophospholipids
apolar
Saturated or unsaturated FAs. Typically C16 or C18.
polar
CH3-N-CH2-CH2- +
Phosphatidylcholine
Phosphatidylethanolamine
Phosphatidylserine
CH3
H3N-CH2-CH2-
OOC
HC-CH2-
H3N - R
Triacyl glycerols are neutral, storage of lipids.
Membrane lipids are polar.

14. II.3 Membrane lipids: 2. Sphingolipids
HO-CH-CH=CH-(CH2)12-CH3
  CH-NH-C-/\/\/\/\/\/-CH3
-CH2 O
Sphingosine (blue area when R = H)
fatty acid
R-O
R Name
-H ceramide
-phosphocholine sphingomyelin
-monosaccharides cerebrosides
-oligosaccharides gangliosides
Tay Sachs disease: impaired degradation of brain gangliosides

15. Glycerophospholipids vs spingolipids
Fig 9.7c Fig 9.10 c

16. II.3 Membrane lipids: 3. Cholesterol (a sterol)
• common in animal membranes
• precursor to several steroid hormones
•VD3
Bile acid
Composition of RBC membranes
Protein 49%
Carbohydrate 8%
Lipid 43%
- glycerophospholipids 48%
- sphingolipids %
- cholesterol %
Autosynthesis:27C
actyl-CoA
NAPDH

17. Cholesterol
For transport and storage, the hydroxyl group condenses with a fatty acid to form a sterol ester

18. Amphipathic lipid aggregates that form in water
Water is excluded
(b) Bilayer © When the bilayer forms in on itself, 3-d hollow vesicle with an aqueous cavity.

19. Cross section of a cell membrane

20. Lipids in the News The ‘good’ & the ‘bad’
AHA: Omega-3 fatty acids benefit the heart of healthy people, and those at high risk of — or who have — cardiovascular disease. Research has shown that omega-3 fatty acids decrease risk of abnormal heartbeats, which can lead to sudden death.  Omega-3 fatty acids also decrease triglyceride levels, lower blood pressure (slightly), and decrease rates of heart attack.

21. Lipids in the News II The bad: What’s the deal with trans fats?
m.p. = 14 °C
m.p. = 45 °C

22. Where do trans fats come from?
Natural fats (which contain cis double bonds) are prone to oxidation and rancidity. This limits their shelf life and usefulness for food preparation.
Hydrogenation (H2 + catalyst) of natural fats reduces the cis double bonds to produce saturated fats which have a longer shelf life. Unfortunately, trans bonds are produced as an unwanted by-product.
The primary health risk identified for trans fat consumption is an elevated risk of coronary heart disease (CHD).

24. Packing of fatty acids into stable aggregates

25. Triacylglycerols contain three fatty acids esterified to a glycerol backbone

26. Triacylglycerols are stored energy in fat cells and plant seeds

27. The greater the percentage of saturated fatty acids in food fats the higher the melting temperature

28. Waxes are esters of long chain fatty acids

29. Common types of storage and membrane lipids

30. Glycerophospholipids, the main lipid component of biological membranes, contain two fatty acids esterified to a glycerol phosphate backbone

31. Glycerophospholipids with ether-linked fatty acids
Abundant in
the heart
Important in
inflammatory
response

32. Glycosphingolipids as determinants of blood groups
Glycosphingolipids contain the blood group antigens present on the surface of red blood cells

33. Bile acids are synthesized from cholesterol Bile acids aid in emulsification of dietary fat in the intestine

34. Other sterols are synthesized from cholesterol

35. Vitamin D is produced in the skin by UV irradiation of 7-dehydrocholestreol

36. Cystic Fibrosis
This is the most common lethal genetic disease in Caucasians of Northern European ancestry, and has a
prevalence of about 1:3,000 births. This autosomal recessive disorder is caused by mutations to the gene for the CF transmembrane conductance regulator (CFTR) protein that functions as a chloride channel on epithelium. Defective CFTR results in decreased secretion of chloride and increased reabsorption of
sodium and water.