1. Medical biochemistry & Molecular Biology Department
Lipids Chemistry
Dr. Magda Ibrahim
Medical biochemistry & Molecular Biology Department
Dr. Magda Ibrahim
Lecturer of medical
biochemistry
and molecular biology

2. State the definition and classification of lipids.
Recognize the general structure and characters of fatty acids.
List the four main classes of unsaturated fatty acids
Define essential fatty acids
Explain the physiological importance of omega 3 fatty acids
Classify phospholipids and state their functions in the body
Describe structure and significance of glycolipids
Describe the steroid nucleus, cholesterol molecule and its derivatives
By the end of this topic, you should be able to :

3. Classification of lipids
Introduction
Definition of lipids
Functions of lipids (energy, Fat soluble vitamins, cell membrane, thermal insulator, electrical insulator)
Classification of lipids
Simple lipid Oil/fat wax
Complex lipids (glycolipid, phosphlipids,sulfolipids, lipoprotein)
Derived lipids (fatty acids, glycerol, keton bodies)
Polyprenoid compound (steroids, terpenes)
Characteristics
Fatty acids (amphipathic, straight chain, even number, saturated/un saturated)
Double bond
Poly unsaturated fatty acids (essential fatty acids) + their function

4. Lipids
Heterogeneous group of compounds which are soluble in organic solvents ( ether, chloroform) and insoluble in water.
For example: fat, oils, steroids, wax
They are related either actually or potentially to fatty acids

5. They are not polymers (not formed of repeating units.
What are polymers? Give an examples
Polymers as polysaccharides, proteins, DNA, RNA.

6. What are the functions of lipids?
Important dietary constituents, because of their high energy value.
Fat-soluble vitamins (DEKA)
it serves as a thermal insulator in the subcutaneous tissues and around certain organs.
Electrical insulators around myelinated nerves
Cell membrane structure.

7. Classification of lipids
Substances associated with lipids
( polyprenoid compounds)
Simple lipids
Compound lipids
Derived lipids

8. 1- Simple lipids (They are ester of fatty acid and alcohol)
Oils or fat (TAG)
They are ester of fatty acid + glycerol
Oil--- liquid at room temp
Fat---solid at room temp
TAG;triacylglycerol
Wax
They are ester of fatty acid + high molecular monohydric alcohol (alcohol has carbon)
Bee wax, lanoline

9. II- Compound lipids (ester or amides of fatty acid+ alcohol+ additional group)
Lipoproteins
Contain proteins
Phospholipids
(contain phosphate)
Sulfolipids
Contain sulfate
Glycolipids
contain carbohydrate

10. III- Derived lipids
Theses are produced from the hydrolysis or digestion of simple or compound lipids.
For example: Fatty acids, glycerol, sphingosine.

11. VI- Polyprenoid compounds
A group of compounds which contains isoprene units
They are two classes:
1- Steroids: are derivatives of the hydrocarbon ring system of cholesterol as cholesterol. Also, fat soluble vitamins (EKA) are synthesized from isoprene units.
2- Terpenes in plants

12. Classification of lipids
Introduction
Definition of lipids
Functions of lipids (energy, Fat soluble vitamins, cell membrane, thermal insulator, electrical insulator)
Classification of lipids
Simple lipid Oil/fat wax
Complex lipids (glycolipid, phosphlipids,sulfolipids, lipoprotein)
Derived lipids (fatty acids, glycerol)
Polyprenoid compounds (steroids, terpenes)
Characteristics
Fatty acids (amphipathic, straight chain, even number, saturated/un saturated)
Double bond
Poly unsaturated fatty acids (essential fatty acids) + their function

13. Fatty acids They are aliphatic carboxylic acid.
They are represented as R-COOH, where R is hydrocarbon chain.
Fatty acids are named after the hydrocarbon of the same number of carbon. The suffix (oic) being substituted for the final (e)
For example:
1C methane (Methanoic) HCOOH
2C Ethane (Ethanoic) CH3-COOH

14. General properties of fatty acid in natural lipid
They are mono carboxylic (only one –COOH-), which is completely ionized in plasma.
- So, fatty acids are amphipathic as it contain
Hydrophilic part
(carboxyl group)
Hydrophobic part
(hydrocarbon chain)

15. (2) They have long straight chains:
Short chain----- up to 5 carbon
Medium chain carbon
Except, phytanic acid is branched
(3)Most naturally fatty acids have even number of carbon atoms (they are synthesized from 2-carbon unit).Plants and marine organsim have odd number fatty acids.
Some fatty acids contain a hydroxyl group (cerebronic acid)

16. Saturated fatty acids

17. Unsaturated fatty either mono or poly- unsaturated
(4)May be saturated or unsaturated (the presence of double bound called unsaturated)
Unsaturated fatty either mono or poly- unsaturated
The double bound are always separated from each other by methylene group (-CH2-)
They are neither adjacent nor conjugated (conjugated i.e alternating with single bonds)
Saturated fatty acid
Un-saturated fatty acid

18. The presence of double bound produces Cis-trans isomerism
- The two bulky groups are at the same side of the bond (cis).
- The hydrocarbon chain bent 120 at the double bond giving an L- shape
-Nearly all fatty acid in cis form
The two bulky groups are at the opposite side of the bond (Trans)

19. Compare between cis and trans isomers
Cis- isomers
The two bulky groups are at the same side of the bond
Less thermal stable, the have lower melting temp
Melting temp:
the temperature at which a substance changes from solid to liquid state.
Trans- isomers
The two bulky groups are at the opposite side of the bond
More thermal stable, need high melting temp.
They are products the process of hydrogenation of oil
The are nearer to corresponding saturated fatty acid. They are metabolized like saturated fatty acids. So, they tend to increase cholesterol in blood.

20. French fries, doughunts, and cookies are rich in trans fatty acids.
Try to avoid these food in diet.
Trans fatty acids tend to increase cholesterol level.

21. The melting point of fatty acid decreases if the fatty acids are shorter and have more double bonds
Short fatty acids (up to 5C) and medium chain fatty acids (6-10C) are liquid at room temp.
Longer chain fatty acids (more than 10C) are solid at room temp.
Unsaturated fatty acids have low melting temp and are liquid at room temp.

22. General properties of fatty acid in natural lipids
Amphipathic
Straight chain
Even number
May be saturated or not

23. The presence of double bond in fatty acid is characterized by:
1- separated by methylene (CH2) bridges
2- Not adjacent
3- not conjugated
4- Cis-trans isomers

24. Classification of lipids
Introduction
Definition of lipids
Functions of lipids (energy, Fat soluble vitamins, cell membrane, thermal insulator, electrical insulator)
Classification of lipids
Simple lipid Oil/fat wax
Complex lipids (glycolipid, phosphlipids,sulfolipids, lipoprotein)
Derived lipids (fatty acids, glycerol, keton bodies)
Polyprenoid compound (steroids, terpenes)
Characteristics
Fatty acids (amphipathic, straight chain, even number, saturated/un saturated)
Double bond (separated by methylene group, not adjacent/not conjugated, cis/trans isomers)
Poly unsaturated fatty acids (essential fatty acids) + their function

25. Numbering of fatty acids
CH3-CH2-CH2-CH2-CH2-COOH
Δ numbering
Greek lettering ε δ γ β α
ω (omega) ω-1 ω-2 ω-3 ω ω-5
Palmitic: 16:0
Oleic acid: 18:1 Δ9 1= double bond Δ 9= double bond between 9-10

26. 1- The double bond can be related to the carboxyl (C1)
Oleic C:18:1(9)
or C18: 19
The double bond is between 9 and 10 26

27. 2- The double bond can be related to the ω (omega) carbon of the fatty acid - Unsaturated FA are classified into ώ 3,6,7 and Family
CH3-(CH2)7-CH=CH-(CH2)7-COOH
Oleic : 19 or 18:19 class:9 family
CH3-(CH2) 4CH=CH-CH2-CH=CH-(CH2) 7-COOH
Linoleic 18: 29 ,12 or18:26,9 class:6family 27

28. Parent fatty acids

29. Classification of lipids
Introduction
Definition of lipids
Functions of lipids (energy, Fat soluble vitamins, cell membrane, thermal insulator, electrical insulator)
Classification of lipids
Simple lipid Oil/fat wax
Complex lipids (glycolipid, phosphlipids,sulfolipids, lipoprotein)
Derived lipids (fatty acids, glycerol, keton bodies)
Polyprenoid compounds (steroids, terpenes)
Characteristics
Fatty acids (amphipathic, straight chain, even number, saturated/un saturated)
Double bond (separated by methylene group, not adjacent/not conjugated, cis/trans isomers)
Poly unsaturated fatty acids (essential fatty acids) + their function

30. Essential fatty acids Can't synthesized inside the body
They are polyunsaturated fatty acids
Can't synthesized inside the body
The are required for normal growth.
They are linoleic acid (ω-6), Linolenic (ω-3), arachidonic acid.
They must be in diet for synthesis of other members of ω-3, ω-6.

31. Essential fatty acids Linoleic acid (18:2 Δ9,12 ω6)
Constitutes about 60-80% of total fatty acid in dietary oils as corn oil, sunflower oil.
Linolenic acid (18:3 Δ9,12 ,15 ω3):
Present in small amount in plant oil, particularly in linseed oil

32. Arachidonic acid (20:4 Δ5,8,11,14 ω6)
Present in (Arachis oil) Peanut oil.
It may not be essential to take it in diet if there is an adequate supply of linoleic acid.
It can be synthesized in side the body from linoleic.

33. Arachidonic acid
20 carbons contains 4 double bonds more kinked
U shape very important in fluidity of biological membrane

34. What about ω-7, ω-9, are they essential fatty acid???
They can be synthesized in side the body, so they are not essential fatty acids

35. Do you know others ω3 fatty acids?
Eicosapentaenoic acid (20:5)
Docosahexaenoic acid (22:6)
Both of them present in fish oil (Salmon).
They protect from cardiovascular diseases
Why Eskimos have low susceptibility to heart diseases?????

36. The importance of essential fatty acid
Synthesis of prostaglandins and thromboxanes (Eicosanoids)
Enter in cell membrane structure
Lower the cholesterol level
Role of Linolenic acid in the formation of docosahexaenoic (DHA) acid (22:6 3), DHA is needed for the brain & retina (its deficiency leads to a condition called retinitis pigmentosa).
Role in growth and development.

37. Characteristics of double bond Numbering of fatty acids
Characteristics of Fatty acids
fatty acids (Amphipathic, Even number, straight chain, double bond)
Function of fatty acids (energy, fat soluble vitamins, thermal/ electerical insulator, cell membrane)
Polyunsaturated fatty acids
Function of Polyunsaturated fatty acid
Characteristics of double bond
Separated by methylene bridge
Not adjacent/ not conjugated
Cis/ trans isomers
Comparison between cis/trans isomers
Melting temp. ( low melting temp is in cis form unsaturated fatty acids, short/ medium chain fatty acids
Numbering of fatty acids
Δ delta numbering (from COOH) Δ1,Δ2,Δ3
GreeK lettering (from COOH) …..α, β,α
Omega numbering (from CH3) …..ω1,ω2,ω3

38. Classification of lipids
Substances associated with lipids
( polyprenoid compounds)
Simple lipids
Compound lipids
Derived lipids

39. Triacylglycerol
They are esters of alcohol glycerol and three fatty acids
If the three fatty acids are the same-----Simple Triacylglycerol
If the three fatty acids are not the same------Mixed Triacylglycerol
Triacylglycerol may be fluid or soild …………….When?????

40. Function of triacylglycerol
Main storage form of fat.
Can be stored in large amount as it is hydrophobic
It provides the body with high energy
It acts as insulator for heat.
It supports internal viscera.

41. Mixed lipids Phospholipids Glycolipid (Glycospingolipids)
Glycero-phospholipids
Sphingo-phospholipids
(Sphingomylein)

42. Plasmalogen

43. Phosphatidic acid
An Intermediate in the synthesis of TAG, phospholipid (parent compounds)
is not common constituents in tissues.

44. Glycerophospholipids
It contain glycerol + 2 fatty acids attached to C1,2 + phosphate group attached to C3+ base or alcohol
Usually saturated fatty acid
Usually unsaturated fatty acid
Ethanol, choline, serine, inositol, glycerol

45. Types of Glycerophospholipids
(3)
(2)
(1)
Choline
Serine or
ethanolamine
Phosphatidyl choline ( lecithin)
Dipalmityl lecithin =lung surfactant
Phosphatidyl serine/ ethanolamine
(cephalins)
They have role in blood coagulation

46. Types of phospholipids
(5)
(4)
Stearic acid
Arachidonic acid
inositol
Plasmalogens
They resemble phospholipids, except:
Have ether link in C1 not ester
Alcohol in C1
Ethanolamine plasmalogen present in brain
Phosphatidyl inositol
Phosphatidyl inositol 4,5 bisphosphate has a role in signaling transduction

47. Types of phospholipids
(6)
(7)
Cardiolipin
(Diphosphatidyl glycerol)
Present in mitochondrial memb.
glycerol
Phosphatidyl glycerol
- Present in mitochondrial memb.

48. Types of phospholipids
(8)
lysolecithin
Lysophospholipid (lysophosphatidyl choline)
-is phospholipid with free OH in C2

49. Glycerophospholipids
1- Phosphatidyl choline (lecithin)
e.g dipalmitoyl lecithin (lung surfactant).
2- phosphatidyl serine/ ethanolamine (cephalins) have a role in blood coagulation.
both 1- 2 are the most of phospholipids in tissue
5- Phosphatidyl glycerol present in mitochondria.
6- Diphosphatidyl glycerol (cardiolipin) presents in mitochondrial membrane and had immunological properties
3- Phosphatidyl inositol e.g Phosphatidyl inositol 4,5 bisphosphate has a role in signal transduction and cell membrane
4-Plasmalogens e.g plasmalogens ethanolamine in brain (had ether link at C1+ and unsaturated alcohol at C1
7- Lysophospholipids:
they are phosphoacylglycerol, metabolic intermediates of phospholipids ( no fatty acid in C2).
8- Phosphatidic acid is an intermediates of triacylglycerol & phospholipid synthesis. Not present in tissue structure.

50. Important Notes
Most phospholipids contain more than one kind of fatty acids.
Saturated fatty acid is attached to C1. While, unsaturated fatty acid is attached to C2 except in Dipalmityl lecithin
Phospholipase A2 enzyme attacks C2 position

51. Did you remember 5 types of phospholipids?
Of course……NO

52. Mixed lipids Phospholipids Glycolipid (Glycospingolipids)√
Glycero-phospholipids
Sphingo-phospholipids
Sphingomyelin √

53. Sphingomyelin Sphingosine = Serine+ fatty acid (palmitate)
The backbone is sphingosine
Sphingosine = Serine+ fatty acid (palmitate)
Ceramide= Sphingosine+ fatty acid
Sphingomyelin= ceramide + Phosphocholine
Sphingomylein is present in cell membrane and myelinated nerve fiber.

54. Sphingomyelin
Sphingomyelin= ceramide + Phosphocholine

55. Functions of phospholipids
(1)Structural component of membranes
(2) Enter in lipoprotein structure, which help in lipid transport in body
Transport of triacylglycerol from liver to body, any defect lead to fatty liver
(3) Solubilize cholesterol in bile, any defect lead to cholesterol stones

56. Special function of phospholipids
Dipalmitoyl Phosphatidyl choline = Dipalmitoyl lecithin= Lung surfactant
It contains palmitic acid at C1,2
It decrease the surface tension in the lung alveoli.
So, it prevent adherence of the inner surfaces of the lung.
It is synthesized around time of birth.

57. Lung surfactants (dipalmitoly lecithin)
At, birth if decrease----- it leads to “RDS” respiratory distress syndrome

58. Phosphatidyl inositol 4,5 bisphosphate:
Act as second messenger in signal transduction
Acidic phospholipids: which have (-) net charge at physiological PH
- Phosphatidyl serine, inositol, glycerol and cardiolipin
They play a role in blood coagulation.
Antibodies against acidic phospholipids recurrent thrombosis and recurrent fetal loss (antiphospholipids syndrome)

59. Mixed lipids Phospholipids Glycolipid (Glycospingolipids)
Glycero-phospholipids
Sphingomylein √ √

60. Glycolipids (glycosphingolipids)
They are complex of lipids
Ceramide + carbohydrate
Sphingosine +fatty acid =N-acyl sphingosine
Carbohydrate

61. Gangliosides Sulfatides
Types of glycolipids
Gangliosides
Ceramide+ two or more monosaccharides+ one or more sialic acid (NANA) (N-acetyl neuraminic acid )
-ganglion cells of CNS
-act as receptor or
for cell- cell recognition
Sulfatides
galactocerebroside +
sulfate
Cerebrosides
(ceramide hexosamide)
ceramide is attached to monosaccharide unit by β-glycosidic bond
Two types of cerebrosides
Galactocerebrosides
Present in brain & nervous tissue
Glucocerebrosides
Present in extra neural tissue

62. Remember All Glycolipids & Sphingomylein contain sphingosine
All glycerophospholipids contain glycerol
All Glycolipids & Sphingomylein contain sphingosine

63. Mention 4 diseases that are related to phospholipids abnormalities
Mention 4 diseases that are related to phospholipids abnormalities? What are sphingolipids?

64. Steroids (Sterols) √ Are the compounds that have steroid nucleus.
Steroid nucleus is composed of 4 rings identified by A-B-C-D, and formed of 19 carbons √

65. Cholesterol Is the major sterol in animal tissue Cholesterol has 27C
OH- attached to C3
(amphipathic)

66. May be esterified with unsaturated fatty acid (cholesterol ester).
Cholesterol ester is the storage form inside the cell
Blood cholesterol is either in free form(1/3) or in ester form (2/3).

67. Cholesterol is the precursor of :
Steroid hormones: sex hormones, glucocorticoids,mineralocorticoids
Vitamin D3
Bile acids

68. Plant sterol is ergosterol is the precursor of Vit D2
Bacteria do not contain sterol