1. LIPIDS

2. Definition: Made up of C, H and O Lipids are hydrophobic compounds.
insoluble or poorly soluble in water,
Readily soluble in non-polar solvents such as ( ether, benzene, acetone, chloroform)

3. Biological Functions of Lipids
As an energy source, lipids provide 9 kcal of energy per gram
Triglycerides provide energy storage in adipocytes
Phosphoglycerides, sphingolipids, and steroids are structural components of cell membranes
Steroid hormones are critical intercellular messengers
Lipid-soluble vitamins (A, E, D, K)
Dietary fat acts as a carrier of lipid-soluble vitamins into cells of small intestine
Provide shock absorption and insulation

4. Biomedical importance of lipids:
They are a major source of energy; the yield from the oxidation of fatty acids is
9 kcal/g fat compared to 4 kcal/g protein or carbohydrate.
2. Fat stored in adipose tissue serves as thermal insulator in the subcutaneous tissue and protective around certain organs (e.g. kidney).
3. Lipids act as electrical insulators in myelinated nerves to allow rapid propagation of nerve impulses.

5. 4. Cholesterol is an important constituent of the cell membrane and is essential for the synthesis of steroid hormones, bile acids and vitamin D.
5. Fat-soluble vitamins, steroid hormones and eicosanoids play important regulatory roles in the body.

6. 7. Lipoproteins (e.g. LDL & HDL) are a mean
for transporting lipids in blood.
8. Imbalance in lipid metabolism can lead to
major clinical problems such as obesity and atherosclerosis

7. Fatty Acids Fatty acids are water-insoluble.
Long straight-chain carboxylic acids
no branching
Most common chains range from 10–20 carbons in length
Can be saturated (containing no double bonds) or unsaturated (containing one or more double bonds that are always separated at 3 carbon intervals), but usually no other functional groups present
The general formula of saturated fatty acids is: CH3 - ( CH2)n – COOH
Any fatty acid that cannot be synthesized by the body is called an essential fatty acid

10. Fatty Acid Nomenclature
Nomenclature reflects location of double bonds
also used are common names (e.g., oleic, stearic, palmitic)

11. Carbon atoms in a fatty acid are numbered by 2 different systems:
Beginning from the carboxyl carbon
(Δ delta end) as carbon 1, where
numeric designation of the fatty acid shows the number of carbon atoms
2- followed by the number of double bonds,
3- then the site of unsaturation. 4 2 16 1 3 15
COOH

12. Palmitic acid:
CH3(CH2)14COOH ; 16:0
(16:0 indicates a fatty acid with carbons and no double bonds).
Oleic acid:
CH3(CH2)7C=C(CH2)7COOH ; 18:1 Δ 9
(18:1 Δ 9 indicates a fatty acid with 18 carbons and one double bond between carbons 9 and 10).

13. Linoleic acid:
CH3 (CH2) 4C=CCH2C=C(CH2) 7COOH ; 18:2 Δ 9,12
(18:2 Δ 9,12 indicates a fatty acid with 18 carbons and 2 double bonds between carbons 9 and 10 and carbons 12 and13).
Linolenic acid:
CH3CH2C=CCH2C=CCH2C=C(CH2) 7COOH; 18:3 Δ 9,12,15
(18:3 Δ 9,12,15 indicates a fatty acid with 18 carbons and 3 double bonds between carbons 9 and 10, carbons 12 and 13 and carbons 15 and 16).

14. Arachidonic acid:
CH3 (CH2) 3(CH2C=C) 4(CH2) 3COOH; 20:4 Δ 5,8,11,14
(20:4 Δ 5,8,11,14 indicates a fatty acid with 20 carbons
and 4 double bonds between carbons 5 and 6,
carbons 8 and 9, carbons 11 and 12 and
carbons 14 and 15).

15. 2. Beginning with the terminal methyl carbon
(known as omega ώ carbon) as carbon 1,
where ώ-3 for example indicates that;
The closest double bond to the terminal methyl
group begins after 3 carbons from that end.
Therefore,
linoleic acid ; is an ώ -6 fatty acid
CH3 (CH2) 4C=CCH2C=C(CH2) 7COOH
ώ -6,18:2 Δ 9,12
linolenic acid ;is an ώ -3 fatty acid.
CH3CH2C=CCH2C=CCH2C=C(CH2) 7COOH
ώ -3,18:3Δ9,12,15

16. Fatty Acid Properties
Melting point increases with increasing carbon number
Melting point of a saturated fatty acid is higher than an unsaturated fatty acid with the same number of carbons
Typical saturated fatty acids are tightly packed together
cis double bonds prevent good alignment of molecules in unsaturated fatty acids leading to poor packing
Double bonds lower melting point relative to saturated acid

17. Common Fatty Acids

18. Saturated & Unsaturated Fatty Acids
A. Saturated Fatty Acids:
No of Double Bonds
No of Carbon Atoms
Name 12
Lauric (12:0) 14
Myristic (14:0) 16
Palmitic (16:0) 18
Stearic (18:0)
Saturated fatty acids do not have double bonds.
They are formed inside the body.

19. Saturated Fatty Acids
Octanoic Acid

20. B. Unsaturated Fatty Acids:
No of Double Bonds
No of Carbon Atoms
Name 1 16
Palmitoleic (16:1) 18
Oleic (18:1) 2
Linoleic (18:2) 3
Linolenic (18:3) 4 20
Arachidonic (20:4)
The first double bond is usually at the ninth carbon
The double bond is normally in a cis configuration
Double bonds lower the melting temperature
The cis configuration doesn’t allow fatty acids to pack as close together

21. Saturated vs. Unsaturated Fatty Acids
saturated: the SFA’s of a lipid have no double bonds between carbons in chain
polyunsaturated: more than one double bond in the chain
most common polyunsaturated fats contain the polyunsaturated fatty acids (PUFAs) oleic, linoleic and linolenic acid
unsaturated fats have lower melting points
stearic (SFA) melts at 70oC, oleic (PUFA) at 26oC

22. Unsaturated fatty acids have one or more double bonds
Unsaturated fatty acids have one or more double bonds. There are 2 types:
Essential fatty acids:
These fatty acids are with more than one double bond, e.g. linoleic, linolenic and arachidonic,
they are not formed in the body and should be obtained from the diet.
Non-essential fatty acids: These can be synthesized in the body.

23. Unsaturated Fatty Acids
3 - Octenoic Acid
3, 6 - Octadienoic Acid
Short hand: 8:1 (D3)
8:2 (D3,6)

24. Polyunsaturated Fatty Acids
Linoleic acid: Cis, cis, 9, 12 - Octadecadienoic acid
Linolenic acid: Cis, cis, cis 9, 12, 15 - Octadecatrienoic acid
Arachidonic acid: Cis, cis, cis, cis 5, 8, 11, 14 - Eicosatetraenoic acid
Linoleic Acid
Linolenic Acid
Arachidonic Acid

25. Saturated vs. Unsaturated Fats
saturated fats tightly packed, clog arteries as atherosclerosis
because of double bonds, polyunsaturated fats do not pack well -- like building a wall with bricks vs. irregular-shaped objects
plant fats are much higher in PUFA’s than animal fats

26. Cis And Trans Fatty Acids
Cis 9 - Octadecenoic Acid (oleic)
Trans 9 - Octadecenoic Acid (elaidic acid)

27. Naturally-occurring fatty acids
1. Cis form
2. Not conjugated --- isolated double bond.
3. Even numbered fatty acids.

28. CLASSIFICATION OF FATTY ACIDS PRESENT AS GLYCERIDES IN FOOD FATS
Common Name
Systematic Name
Formula
Common source
I. Saturated Fatty Acids
Butyric
Butanoic
CH3(CH2)2COOH
butterfat
butterfat, coconut and palm nut oils
Caproic
Hexanoic
CH3(CH2)4COOH
Caprylic
Octanoic
CH3(CH2)6COOH
coconut and palm nut oils, butterfat
Capric
Decanoic
CH3(CH2)8COOH
coconut and palm nut oils, butterfat
Lauric
Dodecanoic
CH3(CH2)10COOH
coconut and palm nut oils, butterfat
Myristic
Tetradecanoic
CH3(CH2)12COOH
coconut and Palm nut oil, most animal and plant fats
Palmitic
Hexadecanoic
CH3(CH2)14COOH
practically all animal and plant fats
Stearic
Octadecanoic
CH3(CH2)16COOH
animal fats and minor component of plant fats
Arachidic
Eicosanoic
CH3(CH2)18COOH
peanut oil

29. II. Unsaturated Fatty Acids
Common Name
Systematic Name
Formula
Common source
II. Unsaturated Fatty Acids
A. Monoethenoic Acids
Oleic
Cis 9-octadecenoic
C17H33COOH
plant and animal fats
Elaidic
Trans 9-Octadecenoic
C17H33COOH
animal fats
B. Diethenoic Acids
peanut, linseed, and cottonseed oils
Linoleic
9,12-Octadecadienoic
C17H31COOH
C. Triethenoid Acids
9,12,15-Octadecatrienoic
C17H29COOH
linseed and other seed oils
Linolenic
Eleostearic
9,11,13-Octadecatrienoic
C17H29COOH
peanut seed fats
D. Tetraethenoid Acids
fish oils
Moroctic
4,8,12,15-Octadecatetraenoic
C17H27COOH
Arachidonic
5,8,11,14-Eicosatetraenoic
C19H31COOH
traces in animal fats

30. Common and Systematic Names of Fatty Acids
Common Name
Systematic Name
Formula
Common source
A. Monoethenoic Acids
Cis 9-octadecenoic
C17H33COOH
plant and animal fats
Oleic
Trans 9-Octadecenoic
C17H33COOH
animal fats
Elaidic
B. Diethenoic Acids
9,12-Octadecadienoic
C17H31COOH
peanut, linseed, and cottonseed oils
Linoleic
C. Triethenoid Acids
Linolenic
9,12,15-Octadecatrienoic
C17H29COOH
linseed and other seed oils
9,11,13-Octadecatrienoic
C17H29COOH
peanut seed fats
Eleostearic
D. Tetraethenoid Acids
Moroctic
4,8,12,15-Octadecatetraenoic
C17H27COOH
fish oils
Arachidonic
5,8,11,14-Eicosatetraenoic
C19H31COOH
traces in animal fats

31. Biomedical importance of fatty acids:
Human body can synthesize various fatty acids with the exception of;
“linoleic” and “linolenic” acids; this is because body tissues cannot introduce double bonds beyond the Δ 9 position.
In contrast, plants are able to introduce double bonds at the Δ 12 and Δ 15 positions.
Therefore, linoleic acid and linolenic acid are considered as nutritionally essential fatty acids,
and must be supplied in a diet of plant origin or from animals that have consumed these plant fats.

32. 1. Dietary ώ -3 fatty acids (in fish oil and plant fats)
can reduce serum triglycerides, thrombosis and
the risk of cardiovascular mortality.
2- ώ -6 fatty acids (in olive oil and corn oil)
lower plasma cholesterol and protect against coronary heart disease.
3-Generally, a high ratio of polyunsaturated fatty
acids to saturated fatty acids in the diet is a major factor to prevent coronary heart disease.

33. Eicosanoids: Prostaglandins, Leukotrienes, and Thromboxanes
Fatty acids which can’t be synthesized by the body are essential fatty acids
Linoleic acid is an essential fatty acid required to make arachadonic acid
Arachidonic acid (20 C) is the eicosanoid precursor
Eicosanoids are three groups of structurally related compounds
Prostaglandins
Leukotrienes
Thromboxanes

34. Prostaglandins Potent biological molecules
They act like hormones in controlling the body’s processes
Structure
Synthesized from 20-carbon unsaturated fatty acids
Cyclic compounds including a 5-carbon ring
Names are based on ring substituents and number of side-chain double bonds
Made in most tissues
Exert their effects on cells that produce them and cells in the immediate vicinity

35. Biological Processes Regulated by Eicosanoids
Blood clotting
Thromboxane A2 stimulates constriction of blood vessels and platelet aggregation
Prostacyclin dilates blood vessels and inhibits platelet aggregation
Inflammatory response
Prostaglandins mediate aspects of inflammatory response
Reproductive system
Stimulation of smooth muscle by PGE2

36. Biological Processes Regulated by Eicosanoids
Gastrointestinal tract
Prostaglandins inhibit gastric secretion
Inhibition of hormone-sensitive lipases
Prostaglandins increase secretion of protective mucus
Kidneys
Prostaglandins dilate renal blood vessels
Results in increased water and electrolyte excretion
Respiratory tract
Leukotrienes promote the constriction of bronchi
Prostaglandins promote bronchodilation

37. Structures of Four Prostaglandins

38. Aspirin and Prostaglandins
Aspirin inhibits prostaglandin synthesis by acetylating cyclooxygenase, an enzyme necessary for prostaglandin synthesis

39. Overview of Prostaglandin Synthesis From Arachidonic Acid