2. Lipids: Fats & Oils by DR. MUSTANSAR

3. Lipids
energy storage

4. What are Lipids?

5. LIPIDS
Lipids are a group of naturally occurring moleculesthat
include fats, waxes, sterols, fat-soluble vitamins(such as
vitamins A, D, E, and K), monoglycerides,diglycerides,
triglycerides, phospholipids, and others. The main
biological functions of lipids include storing energy,
signaling, and acting as structural components of
cell membranes.Lipids have applications in the cosmetic
and food industries.

6. • - Lipids are insoluble in water, but
soluble in fat or organic solvents (ether,
chloroform, benzene, acetone).
• - Lipids include fats, oils, waxes and
related compounds.
• They are widely distributed in nature
both in plants and in animals.

7. Chemistry of Lipids
Definition:
• - Lipids are organic compounds formed
mainly from alcohol and fatty acids
combined together by ester linkage.
H2O
O
R CH2 OH
+
Fatty alcohol
HO C
R
Fatty acid Esterase (lipase)
O
R CH2 O C
R
ester (lipid)

8. Classification of Lipids
A. Classification by White – based on the presence or absence of
glycerol
1. Fatty acids
2. Lipids containing glycerol
a) Neutral fats (triacylglycerols)
b) Phosphoglycerides or phospholipids
c) Cardiolipin
d) Plasmalogens

9. 3. Lipids not containing glycerol
• a) Sphingolipids
• b) Alipathic alcohol and waxes
• c) Terpenes
• d) Steroids
• e) Prostaglandins
• 4. Lipids combined with other classes of compounds
• a) lipoproteins and proteolipids
• b) Glycolipids

11. Some common classifications of lipids and their general
biologic functions
Lipid
Primary Functions
Fatty acids
Triacylglycerols
Energy sources, biosynthetic precursors
Storage, transport
Phosphoglycerides Membrane components
Ketone bodies
Energy sources
Sphingolipids
Membrane components
Eicosanoids
Modulators of physiologic activity
Cholesterol
Membrane component
Steroid hormones
Modulators of physiologic activity

12. Biological Importance of Lipids:
1.
They are more palatable and storable to unlimited
amount compared to carbohydrates.
2.
They have a high-energy value (25% of body needs) and
they provide more energy per gram than carbohydrates
and proteins but carbohydrates are the preferable source
of energy.

13. 3.
Supply the essential fatty acids that cannot be synthesized
by the body.
4.
Supply the body with fat-soluble vitamins (A, D, E and K).
5.
They are important constituents of the nervous system.
6.
Tissue fat is an essential constituent of cell membrane and
nervous system. It is mainly phospholipids in nature that
are not affected by starvation.

14. • 7-Stored lipids “depot fat” is stored in all human cells acts
as:
• A store of energy.
• A pad for the internal organs to protect them from outside
shocks.
• A subcutaneous thermal insulator against loss of body heat.
• 8-Lipoproteins, which are complex of lipids and proteins, are
important cellular constituents that present both in the
cellular and subcellular membranes.

15. • 9-Cholesterol enters in membrane structure and is
used for synthesis of adrenal cortical hormones,
vitamin D3 and bile acids.
• 10- Lipids provide bases for dealing with diseases such
as obesity, atherosclerosis, lipid-storage diseases,
essential fatty acid deficiency, respiratory distress
syndrome,

16. Bad Things About Fat
• Makes you fat!
• Heart disease, high blood pressure, cancer
• Unsaturated fats are reactive free radicals
Dr. Thomas J. Montville
16

17. Fatty alcohols
1-Glycerol:
• It is a trihydric alcohol (i.e., containing three
OH groups) and has the popular name
glycerin.
• It is synthesized in the body from glucose.
• It has the following properties:

18. 1.
Colorless viscous oily liquid with sweet taste.
2.
On heating with sulfuric acid or KHSO4
(dehydration) it gives acrolein that has a bad odor.
This reaction is used for detection of free glycerol or
any compound containing glycerol.
CH2
HO
OH
CH
CH2
OH
Glycerol
2 H2O
CHO
Heating, KHSO4
CH
CH2
Acrolein

19. • 3-It combines with three molecules of nitric acid
to form trinitroglycerin (TNT) that is used as
explosive and vasodilator.

20. 4-On esterification with fatty acids it gives:
• Monoglyceride or monoacyl-glycerol: one fatty acid +
glycerol.
• Diglyceride or diacyl-glycerol: two fatty acids + glycerol.
• Triglyceride or triacyl-glycerol: three fatty acids +
glycerol.
5-It has a nutritive value by conversion into glucose and
enters in structure of phospholipids.

21. 1. Uses of Glycerol:
2. Glycerol enters in pharmaceutical and cosmetic
preparations.
3. Reduces brain edema in cerebrovascular
disease.
4. Nitroglycerin is used as vasodilator especially
for the coronary arteries, thus it is used in
treatment of angina pectoris. Also, enters in
explosives manufacturing.

22. 5. Glycerol is used in treatment of glaucoma
(increased intraocular pressure)due to its
ability to dehydrate the tissue from its
water content.

23. 2-Sphingosine:
• - It is the alcohol (monohydric) present in
sphingolipids.
• - It is synthesized in the body from serine and palmitic
acid.
• It is not positive with acrolein test.
OH
CH3 (CH2)12 CH
CH CH
Sphingosine
CH NH2
CH2OH

24. Fatty Acids
Definition:
Definition
Fatty acids are aliphatic mono-carboxylic acids that
are mostly obtained from the hydrolysis of natural
fats and oils.

25. • Have the general formula R-(CH2)n-COOH and mostly
have straight chain (a few exceptions have
branched and heterocyclic chains). In this formula
"n" is mostly an even number of carbon atoms (234) with a few exceptions that have an odd
number.
• Fatty acids are classified according to several bases
as follows:

26. Fatty Acid Structure
H H H H H H H H H H H H H H H HHO
H-C--C--C--C--C--C--C--C--C--C--C--C--C--C--C--C--C-C-OH
H H H H H H H H H H H H H H H H H
omega end
alpha end
degree of saturation

27. 6/29/2012
Biochemistry for medics
27

28. Fat Structure
Saturated Fat – Primarily animal sources:
. Polyunsaturated Fat - Primarily plant sources:
meat, poultry, milk, butter, cheese, egg
vegetable oils (corn, safflower, soybean,
yolk
sunflower, canola, etc.), margarine (most),
Plant Sources: chocolate, coconut, coconut
mayonnaise, certain nuts (almonds, filberts,
oil, palm oil,
pecans, walnuts)
Animal Sources: fish
28
Dr. Thomas J. Montville

29. I. According to presence or absence of double bonds they are
classified into:
• A-Saturated Fatty Acids
• They contain no double bonds with 2-24 or more carbons.
• They are solid at room temperature except if they are short
chained.
• They may be even or odd numbered.
• They have the following molecular formula, CnH2n+1COOH.

30. • Saturated fatty acids (no double)
• A-Short chain Saturated F.A. (2-10 carbon).
• a- Short chain Saturated volatile F.A.(2-6 carbon).
• b- Short chain Saturated non volatile F.A.(7-10
carbon).
• B-Long chain Saturated F.A. (more the10 carbon)

31. Saturated Fatty Acid Structure
H H H H H H H H H H H H H H H HHO
H-C--C--C--C--C--C--C--C--C--C--C--C--C--C--C--C--C-C-OH
H H H H H H H H H H H H H H H H H
omega end
alpha end
degree of saturation: single carbon bond

32. Monounsaturated Fatty Acid Structure
H H H H H H H H
H H H H H H H O
H-C--C--C--C--C--C--C--C--C=C--C--C--C--C--C--C--C--C-OH
H H H H H H H H H H H H H H H H H
omega end
alpha end
One double bond

33. Polyunsaturated Fatty Acid Structure
H H H H H
H
H H H H H HH O
H-C--C--C--C--C--C=C--C--C=C--C--C--C--C--C--C--C--C-OH
H H H H H H H H H H H H H H H H H
omega end
> 2 double bonds
alpha end

34. Saturated Fatty Acids
Number of C
atoms
Common Name
Systemic Name
Formula
2
Acetic acid
Ethanoic acid
CH3COOH
4
Butyric acid
Butanoic acid
CH3(CH2)2COOH
6
Caproic acid
Hexanoic acid
CH3(CH2)4COOH
8
Caprylic acid
Octanoic acid
CH3(CH2)6COOH
10
Capric acid
Decanoic acid
CH3(CH2)8COOH
12
Lauric acid
Dodecanoic acid
CH3(CH2)10COOH
14
Myristic acid
Tetradecanoic acid
CH3(CH2)12COOH
16
Palmitic acid
Hexadecanoic acid
CH3(CH2)14COOH
18
Stearic acid
Octadecanoic acid
CH3(CH2)16COOH
20
Arachidic acid
Eicosanoic acid
CH3(CH2)18COOH
22
Behenic acid
Docosanoic acid
CH3(CH2)20COOH

35. a-Volatile short-chain fatty acids:
•
They are liquid in nature and contain (1-6) carbon atoms.
•
water-soluble and volatile at room temperature, e.g., acetic,
butyric, and caproic acids.
• Acetic F.A. (2C )
CH3-COOH.
• Butyric F.A. (4C ) CH3-(CH2)2-COOH.
• Caproic F.A. (6C ) CH3-(CH2)4-COOH.

36. b-Non-volatile short-chain fatty acids:
acids
• They are solids at room temperature and contain 7-10
carbon atoms.
• They are water-soluble and non-volatile at room
temperature include caprylic and capric F.A.
caprylic (8 C ) CH3-(CH2)6-COOH.
• Capric (10 C )
CH3-(CH2)8-COOH.

37. B-Long-chain fatty acids:
• They contain more than 10 carbon atoms.
• They occur in hydrogenated oils, animal fats, butter and coconut
and palm oils.
• They are non-volatile and water-insoluble
• Include palmitic, stearic, and lignoceric F.A.
•
palmitic(16C)
• stearic (18 C )
CH3-(CH2)14-COOH
CH3-(CH2)16-COOH
• lignoceric (24C ) CH3-(CH2)22-COOH

38. B-Unsaturated Fatty Acids
They contain double bond
• monounsaturated
they contain one double bonds .
(CnH2n-1 COOH)
• polyunsaturated
they contain more the one double bond (CnH2n-more than 1
COOH).

39. Nomenclature of Fatty acids
The systematic name for a fatty acid is derived
from the name of its parent hydrocarbon by the
substitution of oic
for the final e.
For example, the C18 saturated fatty acid is called
octadecanoic acid because the parent hydrocarbon is
octadecane.
6/29/2012
Biochemistry for medics
39

40. A C18 fatty acid with one double bond is called
octadecenoic acid; with two double bonds,
octadecadienoic acid; and with three double
bonds, octadecatrienoic acid.
The notation 18:0 denotes a C18 fatty acid with
no double bonds, whereas 18:2 signifies that
there are two double bonds.

41. Nomenclature of Fatty acids(Contd.)
Carbon atoms are numbered from the carboxyl
carbon (carbon No. 1). The carbon atoms adjacent
to the carboxyl carbon (Nos. 2, 3, and 4) are also
known as the α ,β , and carbons, respectively, and
the terminal methyl carbon is known as theω or ncarbon.
6/29/2012
Biochemistry for medics
41

42. • The position of a double bond is represented
by the symbol ∆followed by a superscript
number.
• eg, ∆ 9 indicates a double bond between
carbons 9 and 10 of the fatty acid;

43. Omega 3 and Omega 6 fatty acids
6/29/2012
Biochemistry for medics
43

44. 1-Monounsaturated fatty acids:
1-Palmitoleic acid :
• It is found in all fats.
• It is C16:1∆9, i.e., has 16 carbons and one double bond
located at carbon number 9 and involving carbon 10.
CH3-( CH2 )5CH = CH-(CH2)7 –COOH

45. Trans fats, what were they thinking?
Polyunsaturated >
monounsaturated
Dr. Thomas J. Montville
45

46. Trans Fat
• Men’s Health Article “The Hidden Killer”
• “It’s a fat that’s difficult to digest so it increases the
amount of bad cholesterol in your blood and can
dramatically boost your risk of heart disease. If
saturated animal fats are unhealthy, trans fats are far
worse.”
• “Harvard scientists estimate that trans fats may
contribute to more than 30,000 premature deaths per
year.”
Dr. Thomas J. Montville
46

47. Cis and Trans-Isomers in unsaturated fatty
acids
• Depending upon the orientation of the radicals around
the axis of the double bond• Cis- If the radicals are on the same side of the double
bond
• Trans- If the radicals are on the opposite side
• Oleic acid and Elaidic acid have the same formula but
Oleic acid is cis while Elaidic acid is Trans Fatty acid
6/29/2012
Biochemistry for medics
47

48. Cis and Trans-Isomers in unsaturated fatty acids
• The hydrocarbon chains in
saturated fatty acids are, fairly
straight and can pack closely
together, making these fats solid
at room temperature.
• Oils, mostly from plant sources,
have some double bonds
between some of the carbons in
the hydrocarbon tail, causing
bends or “kinks” in the shape of
the molecules.

49. Cis and Trans-Isomers in unsaturated fatty acids
• Increase in the number of cis
double bonds in a fatty acid
leads to a variety of possible
spatial configurations of the
molecule—eg, Arachidonic
acid, with four cis double
bonds, has "kinks" or a U
shape.

50. 2-Oleic acid
Is the most common fatty acid in natural fats.
It is C18:1∆9, i.e., has 18 carbons and one double bond
located at carbon number 9 and involving carbon 10.
CH3-(CH2)7- CH=CH – (CH2)7-COOH

51. 3-Nervonic acid
(Unsaturated lignoceric acid).
 It is found in cerebrosides.
 It is C24:1∆15, i.e., has 24 carbons and one
double bond located at carbon number 15 and
involving carbon 16.
CH3 – (CH2)7 CH= CH – (CH2)13- COOH

52. 2-Polyunsaturated fatty acids :
(Essential fatty acids):
•
Definition:
•
They are essential fatty acids that can not be
synthesized in the human body and must be taken
in adequate amounts in the diet.
•
They are required for normal growth and
metabolism

53. • Source: vegetable oils such as corn oil,
linseed oil, peanut oil, olive oil, cottonseed
oil, soybean oil and many other plant oils,
cod liver oil and animal fats.
• Deficiency: Their deficiency in the diet leads
to nutrition deficiency disease.

54. • Its symptoms include: poor growth and
health with susceptibility to infections,
dermatitis, decreased capacity to reproduce,
impaired transport of lipids, fatty liver, and
lowered resistance to stress.

55. •
Function of Essential Fatty Acids:
1. They are useful in the treatment of atherosclerosis
by help transporting blood cholesterol and lowering
it and transporting triglycerides.
2. The hormones are synthesized from them.
3. They enter in structure of all cellular and subcellular
membranes and the transporting plasma
phospholipids.

56. 4.
They are essential for skin integrity, normal growth
and reproduction.
5.
They have an important role in blood clotting
(intrinsic factor).
6.
Important in preventing and treating fatty liver.
7.
Important role in health of the retina and vision.
8.
They can be oxidized for energy production.

57. Signs and Symptoms of Essential Fatty
Acids Deficiency
•
•
•
•
•
Flaky, itchy skin
Diarrhea
Infections
Retarded growth and wound healing
Anemia

58. Essential Fatty Acid- Omega-3 (alphalinolenic acid)
H H H H H H H H H H H H H H H HH O
H-C--C--C=C--C--C =C--C--C=C--C--C--C--C--C--C--C--C-OH
H H
H
H
H H H H H H H
omega end
alpha end
1st double bond is located on the 3rd carbon
from the omega end

59. 1-Linoleic:
C18:2∆9, 12.
 It is the most important since other essential
fatty acids can be synthesized from it in the body.
CH3-(CH2)4-CH = CH-CH2-CH=CH-(CH2)7-COOH

60. Essential Fatty Acid- Omega-6 (linoleic
acid)
H H H H H
H
H H H H H H H O
H-C--C--C--C-- C--C =C--C--C=C--C--C--C--C--C--C--C--COH
H H H H H H H H H H H H H H H H H
omega end
alpha end
1st double bond is located on the 6th carbon
from the omega end

61. 2-Linolenic acid:
acid
C18:3∆9, 12, 15,
in corn, linseed, peanut, olive, cottonseed and
soybean oils.
CH3-CH2-CH=CH-CH2-CH=CH-CH2-CH=CH-(CH2)7-COOH

62. 3-Arachidonic acid:
acid
C20:4∆5, 8, 11, 14.
 It is an important component of phospholipids in
animal and in peanut oil from which prostaglandins
are synthesized.
CH3-(CH2)4-CH=CH-CH2-CH=CH-CH2-CH=CH-CH2-CH=CH(CH2)3-COOH

63. 1-Simple Lipids
A-Neutral Fats and oils (Triglycerides)
Definition:
- They are called neutral because they are uncharged
due to absence of ionizable groups in it.
 The neutral fats are the most abundant lipids in
nature. They constitute about 98% of the lipids of
adipose tissue, 30% of plasma or liver lipids, less than
10% of erythrocyte lipids.

64. Triglycerides
H
O
H--C--OH
H
HO-C-R
H--C--O--C-- R + H2O
O
H--C--OH
+
O
HO-C-R
H--C--O--C-- + H20
R
O
H--C--OH
O
HO-C-R
H--C--O--C-- + H20
R
H
Glycerol
O
H
(Ester bond)
Triglyceride +
+ 3 FA’s
3 H20

65. Triglycerides
H
H
H--C--OH
H--C--OH
Fatty Acid
+
Fatty Acid
O
H--C--O--C-- Fatty Acid
O
H--C--O--C--Fatty Acid
Fatty Acid
H--C--OH
H
O
H--C--O--C--Fatty Acid
H
esterification/reesterification
desterfication

66. They are esters of glycerol with various fatty acids.
Since the 3 hydroxyl groups of glycerol are esterified,
the neutral fats are also called “Triglycerides”.
 Esterification of glycerol with one molecule of fatty
acid gives monoglyceride, and that with 2 molecules
gives diglyceride.
O
HO C R1
O
CH2 OH
HO C R2 + HO C H
O
CH2 OH
HO C R3
Fatty acids
Glycerol
O
O
H2C O C R1
R2 C O C H
3 H2O
O
H2C O C R3
Triglycerides
(Triacylglycerol)

67. Types of triglycerides
1-Simple triglycerides: If the three fatty acids
connected to glycerol are of the same type the
triglyceride is called simple triglyceride, e.g.,
tripalmitin.

68. 2-Mixed triglycerides: if they are of different
types, it is called mixed triglycerides, e.g.,
stearo-diolein and palmito-oleo-stearin.
 Natural fats are mixtures of mixed triglycerides
with a small amount of simple triglycerides.

69. O
O
CH2
O
CH3 (CH2)14 C
O
C
O
C
O
C (CH2)14
H
CH2
(CH2)14
CH3
CH3
Tripalmitin
(simple triacylglycerol)
CH2
O
CH3 (CH2)7 CH
CH
(CH2)7
C
O
C
O
O
C
O
O
C (CH2)7 CH
H
CH2
(CH2)16
CH3
CH (CH2)7 CH3
1-Stearo-2,3-diolein
(mixed triacylglycerol)
CH2
O
CH3 (CH2)7 CH
CH
(CH2)7 C
O
C
O
O
C
O
O
C (CH2)16
H
CH2
(CH2)14
1-palmito-2-oleo-3-stearin
(mixed triacylglycerol)
CH3
CH3

70. The commonest fatty acids in animal
fats are palmitic, stearic and oleic acids.

The main difference between fats and
oils is for oils being liquid at room
temperature, whereas, fats are solids.

71. This is mainly due to presence of larger
percentage of unsaturated fatty acids in
oils than fats that has mostly saturated
fatty acids.

72. Physical properties of fat and oils:
1.
Freshly prepared fats and oils are colorless,
odorless and tasteless.Any color, or taste is due
to association with other foreign substances, e.g.,
the yellow color of body fat or milk fat is due to
carotene pigments (cow milk).

73. 2. Fats have specific gravity less than 1 and,
therefore, they float on water.
3. Fats are insoluble in water, but soluble in
organic solvents as ether and benzene.
4. Melting points of fats are usually low, but
higher than the solidification point,

74. Chemical Properties of fats and oils:
oils
1-Hydrolysis:
 They are hydrolyzed into their constituents ( fatty acids and glycerol)
by the action of super heated steam, acid, alkali or enzyme (e.g.,
lipase of pancreas).
 - During their enzymatic and acid hydrolysis glycerol and free fatty
acids are produced.
O
R2
C
O
CH2 O C R1
O C H
O
CH2 O C R3
Triacylglycerol
Lipase or Acid
3 H2O
H2C
HO C
H2C
OH
H
OH
O
R1 C OH
O
+ R C OH
2
R3
O
C OH
Glycerol Free fatty acids

75. 2-Saponification. Alkaline hydrolysis produces
glycerol and salts of fatty acids (soaps).
Soaps cause emulsification of oily material this help
easy washing of the fatty materials
O
O
CH2 O C R1
H2C OH
HO C H
R2 C O C H
O
CH2 O C R3
Triacylglycerol
3 NaOH
H2C OH
O
R1 C ONa
O
+ R C ONa
2
R3
O
C ONa
Glycerol Sodium salts of
fatty acids (soap)

76. 3-Halogenation
 Neutral fats containing unsaturated fatty acids have the ability of
adding halogens (e.g., hydrogen or hydrogenation and iodine or
iodination) at the double bonds.
 - It is a very important property to determine the degree of
unsaturation of the fat or oil that determines its biological value
CH3
(CH2)4
CH
CH
CH2
CH
CH
(CH2)7
COOH
CH
CH
(CH2)7
COOH
I
I
Linoleic acid
2 I2
CH3
(CH2)4
CH
CH
I
I
CH2
Stearate-tetra-iodinate

77. 4-Hydrogenation or hardening of oils:
oils
It is a type of addition reactions accepting
hydrogen at the double bonds of unsaturated fatty
acids.
The hydrogenation is done under high pressure of
hydrogen and is catalyzed by finely divided nickel
or copper and heat.

78. It is the base of hardening of oils (margarine
manufacturing), e.g., change of oleic acid of fats
(liquid) into stearic acid (solid).
It is advisable not to saturate all double bonds;
otherwise margarine produced will be very hard, of
very low biological value and difficult to digest.

79. Hard fat
Oils Hydrogen, high pressure, nickel
(margarine, solid)
(liquid)
(with saturated
(with unsaturated
fatty acids, e.g., stearic)
fatty acids, e.g., oleic)
Advantages for hydrogenated oil or fat are as follows:
1.
It is more pleasant as cooking fat.
2.
It is digestible and utilizable as normal animal fats and oils.
3.
It is less liable to cause gastric or intestinal irritation.
4.
It is easily stored and transported and less liable to rancidity.
Disadvantages of hydrogenated
 fats include lack of fat-soluble vitamins (A, D, E and K) and
essential fatty acids

80. 5-Oxidation(Rancidty)
This toxic reaction of triglycerides leads to unpleasant
odour or taste of oils and fats developing after
oxidation by oxygen of air, bacteria, or moisture.
Also this is the base of the drying oils after exposure to
atmospheric oxygen.
Example is linseed oil, which is used in paints and
varnishes manufacturing

81. Rancidity
Definition:
It is a physico-chemical change in the natural
properties of the fat leading to the development of
unpleasant odor or taste or abnormal color particularly
on aging after exposure to atmospheric oxygen, light,
moisture, bacterial or fungal contamination and/or
heat.
 Saturated fats resist rancidity more than unsaturated
fats that have unsaturated double bonds.

82. Types and causes of Rancidity:
1.
Hydrolytic rancidity
2.
Oxidative rancidity
3.
Ketonic rancidity
1-Hydrolytic rancidity:
rancidity

It results from slight hydrolysis of the fat by lipase from
bacterial contamination leading to the liberation of free fatty
acids and glycerol at high temperature and moisture.

Volatile short-chain fatty acids have unpleasant odor.

83. O
O
CH2 O C R1
R2 C O C H
O
CH2 O C R3
Triacylglycerol
Lipase
3 H2O
H2C OH
HO C H
H2C OH
O
R1 C OH
O
+ R C OH
2
R3
O
C OH
Glycerol Free fatty acids
(volatile, bad odor)

84. 2-Oxidative Rancidity:
Rancidity
It is oxidation of fat or oil catalyzed by exposure to
oxygen, light and/or heat producing peroxide
derivatives which on decomposition give substances, e.g.,
peroxides, aldehydes, ketones and dicarboxylic acids that
are toxic and have bad odor.
This occurs due to oxidative addition of oxygen at the
unsaturated double bond of unsaturated fatty acid of oils.

85. Polyunsaturated fatty acid
Oxidant, O2
Peroxyradical
Cyclic peroxide
Hydroperoxide
Aldehydes
such as malondialdehyde
Hydroxy fatty acid
Other fragments
such as dicarboxylic acids

86. 3-Ketonic Rancidity:
It is due to the contamination with certain fungi such
as Asperigillus Niger on fats such as coconut oil.
 Ketones, fatty aldehydes, short chain fatty acids and
fatty alcohols are formed.
Moisture accelerates ketonic rancidity.

87.  Prevention of rancidity is achieved by:
1. Avoidance of the causes (exposure to light,
oxygen, moisture, high temperature and bacteria
or fungal contamination). By keeping fats or oils
in well-closed containers in cold, dark and dry
place (i.e., good storage conditions).

88. 1. Removal of catalysts such as lead and copper that
catalyze rancidity.
2. Addition of anti-oxidants to prevent peroxidation
in fat (i.e., rancidity). They include phenols,
naphthols, tannins and hydroquinones. The most
common natural antioxidant is vitamin E that is
important in vitro and in vivo.

89. Hazards of Rancid Fats:
1.
The products of rancidity are toxic, i.e., causes food
poisoning and cancer.
2.
Rancidity destroys the fat-soluble vitamins (vitamins A, D, K
and E).
3.
Rancidity destroys the polyunsaturated essential fatty acids.
4.
Rancidity causes economical loss because rancid fat is
inedible.

90. Analysis and Identification of fats and oils
(Fat Constants)

Fat constants or numbers are tests used for:
1.
Checking the purity of fat for detection of adulteration.
2.
To quantitatively estimate certain properties of fat.
3.
To identify the biological value and natural characteristics of
fat.
4.
Detection of fat rancidity and presence of toxic hydroxy fatty
acids.

91. 1-Iodine number (or value):
Definition: It is the number of grams of iodine absorbed by
100 grams of fat or oil.
Uses: It is a measure for the degree of unsaturation of
the fat, as a natural property for it.
Unsaturated fatty acids absorb iodine at their double
bonds, therefore, as the degree of unsaturation
increases iodine number and hence biological value
of the fat increase.

92. It is used for identification of the type of
fat, detection of adulteration and
determining the biological value of fat.

93. 2-Saponification number (or value):
Definition: It is the number of milligrams of KOH
Definition
required to completely saponify one gram of fat.
fat
Uses:
Uses
Since each carboxyl group of a fatty acid reacts with
one mole of KOH during saponification, therefore,
the amount of alkali needed to saponify certain
weight of fat depends upon the number of fatty
acids present per weight.

94. Thus, fats containing short-chain acids will
have more carboxyl groups per gram than
long chain fatty acids and consume more
alkali, i.e., will have higher saponification
number.

95. 3-Reichert- Meissl Number (or value):
Definition: It is the number of milliliters of 0.1 N
KOH required to neutralize the water-soluble fatty
acids distilled from 5 grams of fat. Short-chain fatty
acid (less than 10 carbons) is distillated by steam.

96. Uses: This studies the natural
composition of the fat and is used for
detection of fat adulteration.
 Butter that has high percentage of short-
chain fatty acids has highest ReichertMeissl number compared to margarine.

97. B-Waxes
Definition: Waxes are solid simple lipids
Definition
containing a monohydric alcohol (with a higher
molecular weight than glycerol) esterified to longchain fatty acids. Examples of these alcohols are
palmitoyl alcohol, cholesterol, vitamin A or D.

98. Properties of waxes: Waxes are insoluble in water,
but soluble in fat solvents and are negative for
acrolein test.
Waxes are not easily hydrolyzed as the fats and are
indigestible by lipases and are very resistant to
rancidity.
Thus they are of no nutritional value.

99. 2-Compound Lipids
Definition:
 They are lipids that contain additional substances, e.g.,
sulfur, phosphorus, amino group, carbohydrate, or
proteins beside fatty acid and alcohol.
 Compound or conjugated lipids are classified into the
following types according to the nature of the
additional group:

100. 1. Phospholipids
2. Glycolipids.
3. Lipoproteins
4. Sulfolipids and amino lipids.

101. A-Phospholipids
Definition: Phospholipids or phosphatides are compound lipids,
which contain phosphoric acid group in their structure.
Importance:
Importance
1. They are present in large amounts in the liver and brain as
well as blood. Every animal and plant cell contains
phospholipids.
2. The membranes bounding cells and subcellular organelles are
composed mainly of phospholipids. Thus, the transfer of
substances through these membranes is controlled by
properties of phospholipids.

102. 3. They are important components of the lipoprotein
coat essential for secretion and transport of plasma
lipoprotein complexes. Thus, they are lipotropic
agents that prevent fatty liver.
4. Myelin sheath of nerves is rich with phospholipids.

103. 5-Important in digestion and absorption of neutral
lipids and excretion of cholesterol in the bile.
6-Important function in blood clotting and platelet
aggregation.
7-They provide lung alveoli with surfactants that
prevent its irreversible collapse.

104. 8-Important role in signal transduction across
the cell membrane.
9-Phospholipase A2 in snake venom hydrolyses
membrane phospholipids into hemolytic
lysolecithin or lysocephalin.
10-They are source of polyunsaturated fatty
acids for synthesis of eicosanoids.

105. Sources: They are found in all cells (plant and animal), milk
and egg-yolk in the form of lecithins.
Structure: phospholipids are composed of:
Structure
1.
Fatty acids (a saturated and an unsaturated fatty acid).
2.
Nitrogenous base (choline, serine, threonine, or
ethanolamine).
3.
Phosphoric acid.
4.
Fatty alcohols (glycerol, inositol or sphingosine).

106.  Classification of Phospholipids are classified into
2 groups according to the type of the alcohol
present into two types:
A-Glycerophospholipids: They are regarded as
Glycerophospholipids
derivatives of phosphatidic acids that are the simplest
type of phospholipids and include:

107. 1. Phosphatidic acids.
2. Lecithins
3. Cephalins.
4. Plasmalogens.
5. Inositides.
6. Cardiolipin.
Cardiolipin
B-Sphingophospholipids: They contain sphingosine
B-Sphingophospholipids
as an alcohol and are named Sphingomyelins.
Sphingomyelins

108. A-Glycerophospholipids
1-Phosphatidic acids:They are metabolic intermediates in synthesis of
triglycerides and glycerophospholipids in the body and may have
function as a second messenger. They exist in two forms according
to the position of the phosphate
Polyunsaturated
R2
fatty acid
O
C
O
α 2
CH
β
C
O
H
α
CH2
O
C
Saturated
fatty acid
R1
O
O
P
OH
Phosphate
OH
α
-Phosphatidic acid
O
Phosphate HO
P
α
CH2
β
O
C
H
O
O
C
O
R1
Saturated
fatty acid
Polyunsaturated
α
C
CH2 O
R2
fatty acid
β
-Phosphatidic acid
OH

109. 2-Lecithins:
Definition: Lecithins are glycerophospholipids that
Definition
contain choline as a base beside phosphatidic acid.
They exist in 2 forms α - and β -lecithins. Lecithins
are a common cell constituent obtained from brain
(α -type), egg yolk (β -type), or liver (both types).
Lecithins are important in the metabolism of fat by
the liver.

110. Structure: Glycerol is connected at C2 or C3
with a polyunsaturated fatty acid, at C1
with a saturated fatty acid, at C3 or C2 by
phosphate to which the choline base is
connected. The common fatty acids in
lecithins are stearic, palmitic, oleic, linoleic,
linolenic, or arachidonic acids.

111. Lysolecithin causes hemolysis of RBCs. This partially explains
toxic effect of snake venom,. The venom contains
lecithinase, which hydrolyzes the polyunsaturated fatty
converting lecithin into lysolecithin. Lysolecithins are
intermediates in metabolism of phospholipids.
CH2 O
O
R2
C
O
C
O
C
H
CH2 O
R1
CH3
O
P
O
OH
CH2
α
-Lecithin
CH3
CH3
+
N
O
CH2
CH3
CH2
Choline
O
P
O
OH
β
-Lecithin
CH2
Choline
CH2 O
C
H
CH2 O
N
+
CH3
CH3
O
C
R1
O
C
R2

112. 
Lung surfactant

Is a complex of dipalmitoyl-lecithin, sphingomyelin and a
group of apoproteins called apoprotein A, B, C, and D.

It is produced by type II alveolar cells and is anchored to
the alveolar surface of type II and I cells.

113. It lowers alveolar surface tension and improves gas
exchange besides activating macrophages to kill
pathogens.
 In premature babies, this surfactant is deficient and
they suffer from respiratory distress syndrome.
 Glucocorticoids increase the synthesis of the
surfactant complex and promote differentiation of
lung cells.

114. 3-Cephalins (or Kephalins):
Definition: They are phosphatidyl-ethanolamine or
Definition
serine. Cephalins occur in association with lecithins in
tissues and are isolated from the brain (Kephale =
head).
Structure: Cephalins resemble lecithins in structure
except that choline is replaced by ethanolamine, serine
or threonine amino acids.

115.  Certain cephalins are constituents of the complex mixture of
phospholipids, cholesterol and fat that constitute the lipid
component of the lipoprotein “thromboplastin” which accelerates
the clotting of blood by activation of prothrombin to thrombin in
presence of calcium ions.
ions
CH2 O
O
R2
C
O
C H
O
C
R1
O
CH2 O P O CH2 CH2 NH2 Ethanolamine
OH
HO CH CH COOH Serine
2
α-Cephalin
HO CH
NH2
CH
CH3 NH2
COOH
Threonine

116. 4-Plasmalogens:
Definition: Plasmalogens are found in the cell
membrane phospholipids fraction of brain and
muscle (10% of it is plasmalogens), liver, semen and
eggs.

117. Structure: Plasmalogens resemble lecithins and
Structure
cephalins in structure but differ in the presence of
α ,β -unsaturated fatty alcohol rather than a fatty
acid at C1 of the glycerol connected by ether bond.
 At C2 there is an unsaturated long-chain fatty acid,
however, it may be a very short-chain fatty acid

118. Properties: Similar to lecithins.
CH2 O
O
R2
C
O
C H
CH
CH
α,β-Unsaturated
R1 fatty alcohol
O
CH2 O P O CH2 CH2
OH
α-Plasmalogen
CH3
+ CH
N
3
CH3

119. 5-Inositides:
5-Inositides
 Definition:
 - They are phosphatidyl inositol.
 Structure: They are similar to lecithins or cephalins but they
Structure
have the cyclic sugar alcohol, inositol as the base. They are
formed of glycerol, one saturated fatty acid, one unsaturated
fatty acid, phosphoric acid and inositol
CH2
O
R2
C
O
C
O
C
O
H
CH2 O
R1
OH
O
P
OH
O
1
H
α
-Phosphatidylinositol
2
H
H
6
OH
OH
3
H
H
4
OH
OH
5
H

120. Source: Brain tissues.
Source
tissues
Function:
Function
Phosphatidyl inositol is a major component of cell
membrane phospholipids particularly at the inner
leaflet of it.
 They play a major role as second messengers
during signal transduction for certain hormone..

121. On hydrolysis by phospholipase C,
phosphatidyl-inositol-4,5-diphosphate
produces diacyl-glycerol and inositoltriphosphate both act to liberate calcium
from its intracellular stores to mediate the
hormone effects.

122. 6-Cardiolipins:
 Definition: They are diphosphatidyl-glycerol. They are
found in the inner membrane of mitochondria initially
isolated from heart muscle (cardio). It is formed of 3
molecules of glycerol, 4 fatty acids and 2 phosphate groups.
 Function: Used in serological diagnosis of autoimmunity
diseases.
CH2 O
O
R2
C
O
C H
O
C
O
CH2 O P O
OH
OH
R1
CH2
H C
OH
CH2
Cardiolipin
O P O
O
CH2
H C O C R3
O
R4 C O CH2
O

123. B-Sphingophospholipids
1-Sphingomyelins
 Definition: Sphingomyelins are found in large amounts in
brain and nerves and in smaller amounts in lung, spleen,
kidney, liver and blood.
blood

124. Structure: Sphingomyelins differ from lecithins and
cephalins in that they contain sphingosine as the
alcohol instead of glycerol, they contain two
nitrogenous bases: sphingosine itself and choline.
Thus, sphingomyelins contain sphingosine base, one
long-chain fatty acid, choline and phosphoric acid.
To the amino group of sphingosine the fatty acid is
attached by an amide linkage.

125.  Ceramide This part of sphingomyelin in which the amino group
of sphingosine is attached to the fatty acid by an amide linkage.
 Ceramides have been found in the free state in the spleen, liver
and red cells.
Ceramide
Sphingosine
Fatty acid
OH
CH3
(CH2)12 CH
CH
CH
CH
NH
CH2
O
C
Choline
O
O
P
R1
CH3
O
CH2 CH2
OH
Phosphate
Sphingomyelin
+
N
CH3
CH3

126. B-Glycolipids

Definition: They are lipids that contain carbohydrate
residues with sphingosine as the alcohol and a very longchain fatty acid (24 carbon series).

They are present in cerebral tissue, therefore are called
cerebrosides

Classification: According to the number and nature of
Classification
the carbohydrate residue(s) present in the glycolipids the
following are

127. 1. Cerebrosides. They have one galactose
molecule (galactosides).
2. Sulfatides. They are cerebrosides with sulfate
on the sugar (sulfated cerebrosides).
3. Gangliosides. They have several sugar and
sugaramine residues.

128. 1-Cerebrosides:
 Occurrence: They occur in myelin sheath of nerves and white matter of the
brain tissues and cellular membranes. They are important for nerve
conductance.
 Structure: They contain sugar, usually β-galactose and may be glucose or
lactose, sphingosine and fatty acid, but no phosphoric acid.
Ceramide
Sphingosine
Fatty acid
OH
CH3
(CH2)12 CH
CH
CH
CH
NH
CH2
CH2OH
O
OH
H
Galactose
OH
H
H
H
O
OH
H
Psychosin
Cerebroside
O
C
R1

129.  Types: According to the type of fatty acid and
carbohydrate present, there are 4 different types
of cerebrosides isolated from the white matter of
cerebrum and in myelin sheaths of nerves. Rabbit
cerebrosides contain stearic acid.
1. Kerasin contains lignoceric acid (24 carbons) and
galactose.

130. 2. Cerebron (Phrenosin) contains cerebronic
acid (2-hydroxylignoceric acid) and
galactose.
3. Nervon contains nervonic acid (unsaturated
lignoceric acid at C15) and galactose.
4. Oxynervon contains oxynervonic acid (2-
hydroxynervonic acid) and galactose.

131. 2-Sulfatides:
2-Sulfatides
 They are sulfate esters of kerasin or phrenosin in which the
sulfate group is usually attached to the –OH group of C3 or C6
of galactose. Sulfatides are usually present in the brain, liver,
muscles and testes.
OH
CH3
(CH2)12 CH2
CH
CH
CH
NH
O
C
CH2
OH
H
CH2OH
H
O
OSO3H H
H
OH
O
H
Sulfatides (sulfated cerebroside)
R1

132. 3-Gangliosides:
 They are more complex glycolipids that occur in the gray matter of
the brain, ganglion cells, and RBCs. They transfer biogenic amines
across the cell membrane and act as a cell membrane receptor.
 Gangliosides contain sialic acid (N-acetylneuraminic acid),
ceramide (sphingosine + fatty acid of 18-24 carbon atom length), 3
molecules of hexoses (1 glucose + 2 galactose) and hexosamine. The
most simple type of it the monosialoganglioside,. It works as a
receptor for cholera toxin in the human intestine.
Ceramide-Glucose-Galactose-N-acetylgalactosamine-Galactose
Sialic acid
Monosialoganglioside

134. C-Lipoproteins
 Definition: Lipoproteins are lipids combined with
Definition
proteins in the tissues. The lipid component is
phospholipid, cholesterol or triglycerides. The holding
bonds are secondary bonds.
 They include:
1. Structural lipoproteins: These are widely distributed in
tissues being present in cellular and subcellular
membranes. In lung tissues acting as a surfactant in a
complex of a protein and lecithin. In the eye, rhodopsin
of rods is a lipoprotein complex.

135. 2.
Transport lipoproteins:
 These are the forms present in blood plasma. They are
composed of a protein called apolipoprotein and
different types of lipids. (Cholesterol, cholesterol
esters, phospholipids and triglycerides). As the lipid
content increases, the density of plasma lipoproteins
decreases

136. Plasma lipoproteins can be separated by two methods:
methods
1. Ultra-centrifugation: Using the rate of floatation in
sodium chloride solution leading to their sequential
separation into chylomicrons, very low density
lipoproteins (VLDL or pre-β -lipoproteins), low density
lipoproteins (LDL or β -lipoproteins), high density
lipoproteins (HDL or α -lipoproteins) and albumin-free
fatty acids complex.

137. 2.
Electrophoresis: is the migration of charged particles in an
electric field either to the anode or to the cathode. It
sequentially separates the lipoproteins into chylomicrons,
pre-β -, β -, and α -lipoprotein and albumin-free fatty acids
complex.
complex
Polar lipids
(phospholipids)
Polar apolipoproteins
Nonpolar lipids
(cholesterol and its esters
and triacylglycerols)
Structure of a plasma lipoprotein complex

138. a) Chylomicrons: They have the largest diameter and the
least density. They contain 1-2% protein only and 98-99% fat.
The main lipid fraction is triglycerides absorbed from the
intestine and they contain small amounts of the absorbed
cholesterol and phospholipids.

139. b) Very low-density lipoproteins (VLDL) or pre-β-
lipoproteins: Their diameter is smaller than
chylomicrons. They contain about 7-10% protein and
90-93% lipid. The lipid content is mainly triglycerides
formed in the liver. They contain phospholipid and
cholesterol more than chylomicrons.

140. c) Low-density lipoproteins (LDL) or β-lipoproteins:
They contain 10-20% proteins in the form of
apolipoprotein B. Their lipid content varies from 8090%. They contain about 60% of total blood cholesterol
and 40% of total blood phospholipids. As their
percentage increases, the liability to atherosclerosis
increases.

142. d) High-density lipoproteins (HDL) or α -Lipoproteins: They
-Lipoproteins
contain 35-55% proteins in the form of apolipoprotein A.
They contain 45-65% lipids formed of cholesterol (40% of
total blood content) and phospholipids (60% of total blood
content). They act as cholesterol scavengers, as their
percentage increases, the liability to atherosclerosis
decreases. They are higher in females than in males. Due to
their high protein content they possess the highest density.

143. e) Albumin-free fatty acids complex: It is a
proteolipid complex with 99% protein content
associated with long-chain free fatty acids for
transporting them.

144. Cholesterol:
Importance:  It is the most important sterol in animal tissues as free alcohol
or in an esterified form (with linoleic, oleic, palmitic acids or
other fatty acids).
 Steroid hormones, bile salts and vitamin D are derivatives
from it.

145. Tissues contain different amounts of it that serve a
structural and metabolic role, e.g., adrenal cortex
content is 10%, whereas, brain is 2%, others 0.2-0.3%.
Source: - It is synthesized in the body from acetyl-CoA
(1gm/day, cholesterol does not exist in plants) and is
also taken in the diet (0.3 gm/day as in, butter, milk, egg
yolk, brain, meat and animal fat).

146. Physical propeties:It has a hydroxyl group on C3, a double bond
propeties:
between C5 and C6, 8 asymmetric carbon atoms and a side chain
of 8 carbon atoms.
 It is found in all animal cells, corpus luteum and adrenal cortex,
human brain (17% of the solids).
 In the blood (the total cholesterol amounts about 200 mg/dL of
which 2/3 is esterified, chiefly to unsaturated fatty acids while
the remainder occurs as the free cholesterol.
CH3
CH3
CH3
HO
Cholesterol
CH3
CH3

147.  Chemical properties Intestinal bacteria reduce cholesterol into
coprosterol and dihydrocholesterol.
 - It is also oxidized into 7-Dehydrocholesterol and further
unsaturated cholesterol with a second double bond between C7
and C8. When the skin is irradiated with ultraviolet light 7dehydrocholesterol is converted to vitamin D3. This explains the
value of sun light in preventing rickets.
CH3
CH3
CH3
CH3
CH3
CH3
CH3
CH3
HO
HO
H
Coprosterol,
in feces
H
Dihydrocholesterol,
in blood and other tissues
CH3
CH3

148.  Ergosterol differs from 7-dehydrocholesterol in the side chain.
Ergosterol is converted to vitamin D2 by irradiation with UV
Ergosterol and 7- dehydrocholesterol are called Pro-vitamins D
or precursors of vitamin D.
 - It was first isolated from ergot, a fungus then from yeast.
Ergosterol is less stable than cholesterol (because of having 3
double bonds).
CH3
CH3
CH3
CH3
CH3
HO
HO
7-dehydrocholesterol
CH3
CH3
CH3
Ergosterol
CH3
CH3
CH3

149. Steroids
Steroids constitute an important class of biological
compounds.
 Steroids are usually found in association with fat. They
can be separated from fats after saponification since they
occur in the unsaponifiable residue.
 They are derivatives of cholesterol that is formed of
steroid ring or nucleus.
Biologically important groups of substances, which
contain this ring, are:

150. 1. Sterols.
2. Adrenal cortical hormones.
3. Male and female sex hormones.
4. Vitamin D group.
5. Bile acids.
6. Cardiac glycosides.

151.  General consideration about naturally occurring steroids:
steroids
A typical member of this group is cholesterol. Certain facts have
to be considered when drawing steroid formula:
formula
1) There is always oxygen in the form of hydroxyl or ketone on C3.
2) Rings C and D are saturated (stable).
18
19
CH3
1
9
4
2
HO 3
12 CH3
11 13 17
6
A 5 10 B
C
8
7
Steroid ring
D
14
16
15

152. 3) Methyl groups at C18 C19. In case of vitamin D, the CH3 group
at C19 becomes a methylene group (=CH2) and the ring B is
opened, whereas, this methyl group is absent in female sex
hormones (estrogens).
4) In estrogens (female sex hormones) ring A is aromatic and there
is no methyl group on C10.
18
19
CH3
1
9
4
2
HO 3
12 CH3
11 13 17
6
A 5 10 B
C
8
7
Steroid ring
D
14
16
15

153. Bile acids:
 They are produced from oxidation of cholesterol in the liver
producing cholic and chenodeoxycholic acids that are
conjugated with glycine or taurine to produce glycocholic,
glycochenodeoxycholic, taurocholic and
taurochenodeoxycholic acids. They react with sodium or
potassium to produce sodium or potassium bile salts.
 Their function is as follows:

154. 1.
Emulsification of lipids during digestion.
2.
Help in digestion of the other foodstuffs.
3.
Activation of pancreatic lipase.
4.
Help digestion and absorption of fat-soluble vitamins.
5.
Solubilizing cholesterol in bile and prevent gall stone
formation.
6.
Choleretic action (stimulate their own secretion).
7.
Intestinal antiseptic that prevent putrefaction

155. CH3
CH3
OH CH
3
O
CH3
HO
C
OH
Sodium-tauro or
glyco-cholate
R1 H2N CH2 COO-Na+
Sodium glycate
HO
R1 or R2
CH3
C
O
CH3
OH
Sodium-tauro or
glyco-chenodeoxycholate
R2 H2N (CH2)2 SO3-Na+
Sodium taurate
R1 or R2

156. Ketone bodies
Ketone bodies, which are formed from fatty acids and
carbohydrates, include acetone, acetoacetate, and βhydroxybutyrate.
Ketone bodies are synthesized in liver mitochondria and
released into the blood for use as metabolic fuel by other
tissues. The liver does not use ketone bodies.

157. Ketone bodies
Levels of synthesis are high when the rate of fatty acid
oxidation is high and carbohydrate utilization is low.
This occurs during fasting, starvation, untreated
diabetes, and prolonged alcohol abuse.

159. Ketoacidosis
Ketoacidosis is an imbalance of blood pH caused by
the excessive accumulation of acetoacetate or βhydroxybutyrate, which are weak acids.
Ketosis refers to ketonuria (high urine levels of
ketone bodies) and ketonemia (high blood levels of
ketone bodies).

160. Ketoacidosis
During starvation, ketone bodies are the only
source of fuel, so they are consumed by the body,
and there is no excess to accumulate. In contrast, in
untreated diabetes, blood levels of ketone bodies
may become high enough to produce lifethreatening ketoacidosis

161. Lipids
Lipids are composed of C, H, O

long hydrocarbon chain
Diverse group
fats
 phospholipids
 steroids

Do not form polymers
big molecules made
 of smaller subunits
 not a continuing chain

fat

162. Fat subunits
Structure:

glycerol (3C alcohol) + fatty acid
fatty acid =
long HC “tail” with COOH group at “head”
enzyme
dehydration synthesis

163. Building Fats
Triacylglycerol
3 fatty acids linked to glycerol
 ester linkage = between OH & COOH


164. Dehydration synthesis
dehydration synthesis
enzyme
enzyme
enzyme

165. Why do
humans
like fatty
foods?
Fats store energy
Long HC chain
polar or non-polar?
 hydrophilic or hydrophobic?

Function:

energy storage
very rich
2x carbohydrates
cushion organs
 insulates body

think whale blubber!

166. Saturated fats
All C bonded to H
No C=C double bonds
long, straight chain
 most animal fats
 solid at room temp.

contributes to
cardiovascular disease
(atherosclerosis)
= plaque deposits

167. Unsaturated fats
C=C double bonds in
the fatty acids
plant & fish fats
 vegetable oils
 liquid at room temperature

the kinks made by double
bonded C prevent the
molecules from packing
tightly together
AP Biology
monounsaturated?
poly-unsaturated?

168. Saturated vs. unsaturated
saturated
unsaturated
ü

169. Phospholipids
Structure:

glycerol + 2 fatty acids + PO4
PO4 negatively charged
It’s just like a
penguin…
A head at one
end
& a tail
at the other!
AP Biology

170. Phospholipids
Hydrophobic or hydrophilic?
fatty acid tails = hydrophobic
 PO = hydrophilic head
4
 dual “personality”

It likes water
& also
pushes
it away!
interaction with H2O
is complex & very
important!
AP Biology

171. Phospholipids in water
Hydrophilic heads attracted to H2O
Hydrophobic tails “hide” from H2O

can self-assemble into “bubbles”
bubble = “micelle”
can also form bilayer
early evolutionary stage of cell?
bilayer
AP Biology

172. Why is this important?
Phospholipids create a barrier in water
define outside vs. inside
 cell membranes


173. Phospholipids & cells
Phospholipids of cell membrane
double layer = bilayer
 hydrophilic heads on outside

in contact with aqueous solution
outside of cell and inside of cell

hydrophobic tails on inside
form core

forms barrier between cell &
external environment
Tell them
about
soap!
AP Biology

174. Steroids
ex: cholesterol, sex hormones
4 fused C rings

different steroids created by attaching
different functional groups to rings
cholesterol

175. Cholesterol
Important cell component
animal cell membranes
 precursor of all other steroids

including vertebrate sex hormones

AP Biology
high levels in blood may contribute to
cardiovascular disease

176. Cholesterol
Important component of cell membrane
helps keep
cell membranes
fluid & flexible

177. From Cholesterol → Sex Hormones
What a big difference a few atoms can make!

178. THANKS