Lipids are organic compounds that include fats, oils, waxes, sterols and fat-soluble vitamins. They are made up of fatty acids and their derivatives and are soluble in organic solvents but not in water. Lipids include simple lipids like fats and oils which are esters of fatty acids and glycerol. They also include compound lipids like phospholipids and glycolipids which contain additional components like phosphate groups or carbohydrates. Lipids serve important functions like energy storage, insulation, cell membrane structure and transport of fat-soluble vitamins.

1. LIPIDS

2. LIPIDS
 Are organic substances made up of fatty acids
and their naturally existing compounds and
derivatives.
 a group of naturally occurring compounds, which
have in common a ready solubility in such
organic solvents as hydrocarbons, chloroform,
benzene, ethers and alcohols. They include a
diverse range of compounds, like fatty acids and
their derivatives, carotenoids (yellow-red
pigments found in plants) , terpenes (group of
unsaturated HC, responsible for scent of
plants/oils), steroids and bile acids.

3. LIPIDS
 Lipids are fatty acids and their derivatives,
and substances related biosynthetically or
functionally to these compounds.

4.  are broadly defined as any fat-soluble
(lipophilic), naturally-occurring molecules,
such as fats, oils, waxes, cholesterol,
steroids, fat-soluble vitamins (such as
vitamins A, D, E and K), monoglyceride,
diglyceride, phospholipids, and others.

6. Lipids may be defined according to
whether they are:
 Esters or potential esters
 Soluble in fat solvent such as acetone ,
ether, chloroform, benzene, ether, hexane
and methanol.
 Biologically active, that is, lipids are utilized
by living organisms.

7. Characteristics
 Lipids refer to oils and fats and related
compound. They constitute 2-25% of daily
diet.
 They contain C, H2, O2, P and N
 They are insoluble in water but soluble in
organic solvents.

8.  Chemically they are esters of alcohols and
fatty acids of high molecular weight.
 True fats generally constitute the storage
material for energy in both plants and
animals.
 Fat depot in animals derived from ingested
foods are abundant in subcutaneous and
intramuscular connective tissue.

9.  Constitute a part of the cell wall and play a
role in the permeability of cellular
membranes.

11. Functions of Fats
 Major source of calorie energy especially fatty
acids.
 Insulating material for internal organs
 Structural components of membrane
 Enzyme-co-factor (plays an essential role in the
reaction)
 Vehicle for transport of fat soluble vitamins
 Regulatory substance
 Preventors of some steroid, prostaglandin
hormone and Vit. D.

12.  Important constituent of biomemebranes
notably phospholipids, cholesterol and
glycolipids.
 Thermal insulators in subcutaneous tissue
and around certain organs.
 For transport or as carriers. Lipoprotein
solubilize non polar and hydrophobic
substances.

13.  As precursor of other physiologically
functional substances. Cholesterol is the
precursor of bile acids and salts and
steroidal hormones.
 As hormones. The prostaglandins derived
from polyunsaturated fatty acids whose
potent biological activities are regulatory in
nature.

14. c
Classification of LIPIDS
I. SIMPLE LIPIDS – esters of fatty acids
and glycerol with various alcohols and
the yield on hydrolysis.
A.Neutral Fats – glycerol esters of fatty acids
a. oil – under ordinary conditions are liquid,
made up of higher proportions of
unsaturated fatty acids.

15. b. Fats – under ordinary conditions are solids,
made up of greater percentage of saturated
Fatty acids.
B. Waxes – esters of fatty acids with monohydric
alcohol both of higher molecular weight.

16. II. Compound LIPIDS – lipids in combination with
other compounds which yields on hydrolysis of
some other products beside alcohol and fatty
acids.
A.Phospholipid – contains H2PO4 and nitrogenous
group.
a. lecithin (phosphatidyl choline) contain choline
as nitrogenous base.
b. cephalin –( phosphatidyl ethanolamine) –
contains ethanolamine/serine as nitrogenous
base.
c. Sphingomyelin – splingosine and choline are
the nitrogenous base.

17. B. Glycolipids- contain carbohydrate and
nitrogenous base without phosphorous and
glycerol.
C. Ill –defined lipids – amino acids and sulfolipids
having amino and sulfate groups respectively. Also
known as sulfolipids.
D. Lipoproteins – Those are lipids bound to
proteins. Ex. Chylomicrons, VLDL, LDL and HDL.

18. III. Derived lipids – products of the decomposition of
lipids like fatty acids and glycerol but still
exhibiting the general physical characteristics of
lipids.
a. Saturated and unsaturated fatty acids
b. Mono and diglycerides
c. Alcohols
1.straight chain –products of hydrolysis of waxes
usually water insoluble alcohol of higher
molecular weight.
2. Alcohol containing beta-ionene ring – vitamin A
and some carotenoids.
3. sterols

19. IV. Miscellaneous lipids
a. Alipathic HC – iso-ocatadane from liver, fats
and certain hydrocarbons.
b. Squalene HC – in shark , liver and human
sebum
c. Carotenoids
d. Fat soluble vitamins A,D,E,K.

20. Fatty acids (saturated and
unsaturated) –product of fatty
hydrolysis
Types
Saturated fatty acids – belonging to the acetic
acid series with empirical formula:
CnH2n + 1 COOH or CnH2nO2

21. Name No. of C Chemical Sources
atoms formula
Straight chain 4 C 4 H 8 O2 Butter
butyric acid
Caproic acid 6 C6H12O2 Butter, coconut
and palm
Caprylic acid 8 C8H16O2 ditto
Capric acid 10 C10H20O2 ditto
Lauric acid 12 C12H24O2 Laurel and
coconut oil

22. Sources of saturated FA

23. Coconut palm

24. Myristic acid 14 C14H28O2 Coconut,
nutmeg,
animal fat
Palmitic acid 16 C16H32O2 Plant and
animal fat
Stearic acid 18 C18H36O2 Plant and
animal fat
Arachidic acid 20 C20H40O2 Peanut butter
lard
Lignoceric 24 C24H48O2 Peanut oil,
acid glyco and
phospholipid

25. Myristic acid

26. Arachidic acid

27. Properties of Saturated Fatty acids
Low molecular weight
Solid at ordinary temperature
Low melting point
Volatile
Note those with 4 or less carbons are miscible
with water in all proportions but as the chain
increases, the solubility decreased
proportionately.

28. Unsaturated fatty acids- unstable in air, the
degree of unsaturation varies with the
number of double bonds present in the
structure.
Empirical formula:
CnH2n + 1-2m COOH
Where m stands for the number of double
bonds

29. Name No. of Carbon Chemical Sources
atoms formula
1. Double bond 1 C16H31COOH Butter, fish oils,
Palmitoleic 16 C18H35COOH hen fat
Oleic acid 18 Plant and animal
fat, olive oil
2. Double bonds 2 C18H33COOH Linseed oil, lard,
Linoleic acid 18 cottonseed oil.
3. Double bonds 5 C18H27COOH Linseed oil fish
Linolenic acid 18 liver oil
4. Double bonds 7 C20H27COOH Lecithin,
Arachidonic acid 20 cephalin, butter,
liver fat

30. Linolenic acid, Linoleic acid

31. Oleic acid

32. Cotton seed oil

33. Properties of unsaturated fatty acids
Unstable and reactive due to the presence of
double bonds in their molecules.
Reactivity increases with the increase of the
double bonds degree of unsaturation.
Insoluble in ordinary solvents
Liquid at ordinary temperature, non-volatile.
The greater the degree of unsaturation, the
lower the melting points.

34. Free Fatty Acids (FFA, NEFA, UFA)
Composed of carboxylic acid (COOH) with
long hydrocarbon chains or R- COOH where
the R maybe unsaturated (dehydrogenated
with double bonds) or saturated (without
double bonds)
a. saturated fatty acids
b. unsaturated fatty acids
c. essential fatty acids

35. Essential fatty acids – are polyunsaturated
fatty acids found in structural lipids which
includes.
a. linoleic acid
b. linoleinic acid
c. arachidonic acid

36. These fatty acids (saturated, unsaturated and
essential ) must be present in diet to
prevent:
a. dermatitis
b. poor growth
c. decrease resistance to stress
d. impaired lipid transport

37. Simple lipids
A. Fats (neutral fats)/
Tryglycerides/Triacylglycerol (TAG)- these
are esters of alcohol glycerol and 3 fatty
acids.
They are neutral esters of monobasic fatty
acids with trihydric alcohol, glycerol

38. Structure
CH2-O-CO-R1
CH -O-CO-R2
CH2-O-CO-R3
R with common fatty acid chain (simple
triacylglycerol)
R with different fatty acid chain (mixed
triacylglycerol)

39. Example
Simple
CH2-O-CO-C15-H31 CH2-O-CO-C17-H35
CH -O-CO-C15-H31 CH2-O-CO-C17-H35
CH2-O-CO-C15-H31 CH2-O-CO-C17-H35
Tripalmitoylglycerol Tristearoylglycerol
tripalmitin Tristearin

40. Mixed
CH2-O-CO-C17-H35
CH - O-CO-C15-H31
CH -O-CO-C17-H33

41.  Naturally existing fats are usually of this
type. They do not contain three molecules of
the same fatty acids. There is always a
mixture of acids. These explain the
presence of different fats in different organs
of the same animals.

42. Animal fats contains mostly: palmitic, oleic
and stearic acids.
Butter fat contains mostly: palmitic, oleic,and
butyric and caproic acids in small amounts.
Human fats is mostly oleic acid. It has a
yellowish tinge due to carotene and
xanthophyll pigments derived from ingested
food.

43. TAG is divided into two groups:
1. fats
2. vegetable oils

44. Physiologic consideration
1. These are esters of fatty acids and glycerol
which is the main storage form of lipids
(fats) in man.
2. Stored fats are more efficient in its energy
storage than carbohydrate, because:
a. purity of storage-interaction of lipids and
water are minimal, thus fats can be stored
in its pure form (anhydrous).

45. b. unlimited storage – CHO can be stored
chiefly in the liver and to a lesser extent
skeletal muscle, whereas adipose tissues
covers different parts of organs of the body.
c. Greater ATP yield- the energy yield from
complete oxidation of fatty acids is about
9cal/g in contrast to 4cal/g for CHO and
CHON.

46. 3. The TAG in adipose tissue are continuously
undergoing hydrolysis and reesterification.
The result of this determines the levels of
FFA in the circulating plasma.
4. Excessive CHO intake leads to lipogenesis
and eventually obesity due to provision of
substrate, cofactors and activation of
lipogenetic enzymes in its metabolism.

47. B. Waxes - esters of fatty acids with certain
alcohols-not glycerol and not the sterols.
Properties:
1. Insoluble in water and soluble in fat
solvents.
2. Not easily hydrolyzed as the fats are not
digested by the fat splitting enzymes.

48. 3. From the nutritional standpoints, they have
so many uses from the economic
viewpoint such as:
a. In the manufacture of shoe polishes,
varnish, candles, lubricants and cosmetics.

49. Examples:
a. Bees wax – Secreted by the honey bee to
form the comb. It is a mixture, the chief
constituent being myricyl palmitate.
b. Spermaceti wax- found in the skull of
certain whales and dolphins it is chiefly
cetyl palmitate and used in the
manufacture of candles.
c. Chinese wax/carhauba wax – derived from
cuticle of the leaves.

50. Source of spermaceti wax

51. Bee wax

52. Compound lipids
PHOSPHOLIPIDS- are compound lipids which
contain the phosphate group. They also contain
another non-lipid component. Choline,
ethanolamine, amino acid serine or inositol. They
are subdivided according to the alcohol which they
contain.
They are found in cells of both plants and animals.

53. Types of phospholipids
1. lecithin/phosphatidyl choline
a. present in great quantities in egg yolk,
liver and nervous tissues.
b. derived from the greek word lecithes
meaning yolk.
c. plays an important role in metabolism
d. under physiologic condition lecithin
occurs in the form of zwitter ion.

54. 2. Cephalins/P. serine/ethanolamine
a. nitrogenous base is either ethanolamine
or serine.
b. thromboplastic substance which initiates
the process of coagulation.
c. differs in lecithin only on it nitrogenous
base.
d. found in brain tissues and blood.

55. 3. Sphingomyelin – most abundant
sphingolipid.
a. Phosphatides without glycerol
components.
b.Marked increase in the liver, spleen and
tissues in case of Niemann-Pick’s disease.
c. Fatty acids maybe lignoceric, stearic or
nervonic acid.

56. GLYCOLIPIDS – occurs in nerve tissues,
especially in the white matter of the brains
so they are referred to as the cerebrosides.
The well known cerebrosides are keratin,
phrenosine, nervene and oxynervone.

57. Keratin – lignoceric acid, saturated fatty acids
(may also be found in spleen and liver in
Gaucher’s disease keratin is stored in along
with other lipids in spleen and liver)
Phrenosine – yields cerebronic acid and
hydroxylignoceric acid

58. Oxynervone – oxynervone acid, unsaturated
hydroxylignoceric acid
 Nervone – nervonic acid and unsaturated
lignoceric acid present in nerves.

59. SULFOLIPIDS
These are sulfuric acid esters of
cerebrosides. The sulfate is joined as an
ester to C-6 or C-3 of galactose. 20% of
brain cerebrosides occur as sulfate esters.

60. Derived Lipids
 Products of decomposition of lipids like fatty
acids and glycerol but still exhibiting the
general physical characteristics of lipids.

61.  Tarpenes – are class of compounds
containing multiple of five carbon atoms so
related to each other. It includes essential
oils such as camphor, citral, plant pigments
and vitamin A as well as squalene.
 Steroids – these constitutes a variety of
compounds such as sterols, bile acids, sex
hormones, fat soluble vitamin D. steroids
are found in the non-saponifiable fraction of
lipids. The basic steroid nucleus is called
cyclopentanoperhydrophenanthrene(CPPP).

62. A. Sterols
 CHOLESTEROL
 Representative member of sterols.
 Normal product of animal metabolism.
 It is unsaturated alcohol with 27 carbons.
 Important because of its effect in the
degenerative hardening of the arterial wall
leading to arteriosclerosis.

63. Color reaction test
 Liebermann burchard test – test for
determination of chollesterol in the blood.
That yields into an emeral green color upon
acted by chloroform, acetic anhydride and
conc. Sulfuric acid.

64.  Salkowski test – a test not specific for
cholesterol but may also be used for other
sterols. It yields a bluish red to purple color
when cholesterol is treated with chloroform
and concentrated sulfuric acid.

65. Other sterols
 7-dehydrocholesterol – a precursor of
cholesterol which is found underneath the
skin.
 Ergosterol – the yeast sterol.
 Sitosterols – complex mixture of sterols
occuring in oils and higher plants.

66. B. Bile acids
 Secreted continuously in the and stored in
the gall bladder. It is discharged into bowel
during digestion by the relaxation of the
sphincter of the digestive organs and the
relaxation of the gall bladder.

67. Functions of bile
 Emulsifying fats and preparing them for the
action of trypsin. It aid in the digestion and
absorption of fats. Excellent emulsifying
agents.
 Excretion of certain waste products.

68.  There are four acids that have been isolated
in human bile like:
 Cholic acid
 Deoxycholic acid
 Chemodeoxycholic acid
 Lithocholic acid

69.  They are conjugated to form bile salts. The
two principal bile salts are:
 Sodium glycholate
 Sodium laurocholate
 They function in digestion, helps in
emulsification of fats by lowering the surface
tension of water.

70.  Bile pigements (bilirubin and beliverdin)
 They give bile its characteristic color and are
considered as excretory products.
 Oxidaton and reduction produce a series of
various colored compounds some of which
have received definite names:
 They derived from hemoglobin of worn out
red blood cells.

71. Test for bile pigments
 Gmelin’s test – produces a rainbow or play
of colors when bile reacted with
concentrated nitric acid.

72. C. Steroidal hormones
 1. Adrenocortical hormone . If the adrenal
cortex is removed the animal dies. A partail
loss of the function of the gland results in
retention of K+, increased excretion of Na+
and Cl-, muscle weakness, decreased liver
glycogen, lowered resistance to insulin and
greater sensitivity to cold and stress

73.  Addisons disease. Is a result of
adrenocortical insufficiency and responds to
treatment with extracts from adrenal cortex.
 ACTH. Is secreted by the pituitary.
Stimulated the adrenal cortex to produce
steroid hormone which in turn exert an
inhibitory effect on the pituitary gland. These
steroids contitutes a family of hormones of
which cortisol and aldosterone are the major
representative.

74. Functions of the ACTH
 1. affects metabolism of the food stuff.
 2. maintain proper balance of electrolytes
and control inflammation.
 Adrenal hormones are used in the treatment
of rheumatic fever, arthritis, acute asthma
and a number of other ailments.

75.  Prolonged used of cortisone can have
serious side effects, some of which are
characteristics of Cushing’s syndrome, a
disease in which there is excessive
production of adrenal steroids (including
high blood pressure, wasting of muscle
resorption of bones).

76.  2. Sex Hormones. Both male and female
sex hormones are steroids. The male
hormone, androgens are the generic name
for hormone secreted chiefly by the testes
and responsible for the development of the
secondary sexual characteristics. However
these hormones are also produced in other
tissues such as the adrenals and ovary.

77.  Testosterone. Is the chief testicular
androgen and is secreted by the leydig cells.
 In the female there are two types: estrogen
and progesterone. There are three
estrogens that have been
identified.estradiol, estrone and estriol.

78.  The estrogen controls the ovulation cycle.
They undergo oxidation process in the liver
and subsequently conjugate with sulfate and
glucoronic acid in which they are excreted
in the bile and urine.
 The progesterone is elaborated in the
corpus luteum of the ovary during the post-
ovulatory phase of the menstrual cycle and
in much longer amount during gestation by
both corpus luteum and placenta. They are
required for normal pregnancy.

79. D. Fat soluble vitamins
 Vitamin A (retinol)
 Vitamin D (calciferol)
 Vitamin E (tocopherol)
 Vitamin K (coagulation vitamin)