lipid chemistry 20-04-2022.pptx

MEENAKSHI ACADEMY OF HIGHER EDUCATION AND RESEARCH
DEEMED TO BE UNIVERSITY
Mr.SURESH MALCHI
MSC MEDICAL BIOCHEMISTRY, Ph.D. FULL-TIME SCHOLAR

LIPIDS
 Lipid may be regarded as organic substance relatively
insoluble in water, but freely soluble in nonpolar organic
solvents like ether and alcohol.
 eg: benzene, chloroform, ether, hot alcohol, acetone, etc..

CLASSIFICATION
Lipids are broadly classified into
1.simple lipids
2.complex lipids (compound lipids )
3.derived lipids
4.miscellaneous lipids
5.neutral lipids

Simple Lipids :
• Esters of fatty acids with alcohol
This are mainly 2 types
1.Fats and oils
2.Waxes
1.Fats and oils : These are ester of fatty acid with glycerol
Ex. Triacylglycerol
Fatty acid+ Alcohol
Fatty acid + Glycerol

2.Waxes:
These are ester of fatty acid with Alcohol other than glycerol
• Skin and glands of certain vertebrates secret waxes to protect
their hair and skin.
• Certain biological waxes like beeswax and lanolin (from lamb’s
wool) are widely used in cosmetic industry In the manufacture
of creams , lotions and polishes.
Fatty acid + Alcohol other than glycerol

2.Compound Lipids (Complex lipides):
They are esters of fatty acids with alcohol having additional
group such as phosphate and nitrogenous base, carbohydrate,
protein contain other groups.
They are further classified into
1.Phospholipids
2. Glycolipids
3.Lipoproteins
4.other complex lipids
Fatty acid + Alcohol + Phosphate + Nitrogen base + Carbohydrates + proteins

1.Phospholipids :
Esters of fatty acid with alcohols ,nitrogen base ,phosphate and fatty acid
Phospholipids mainly classified into 2 groups
1.Glycerophospholipides
2.Sphingophospholipides
Glycerophospholipids :
These phospholipid contain glycerol as the alcohol
e.g. lecithin,cephal
Fatty acid + Alcohol + Nitrogen Base + Phosphate
Fatty acid + Nitrogen base + Phosphate +Glycerol

• B. Sphingo phospholipids : These phospholipid contain
Sphingosine as the alcohol
Ex: Sphingomyelin
2. Glycolipids : These lipids contain a fatty acid, carbohydrate
and nitrogenous base.
Glycolipids = FA + NB + Sphingosine+
Ex: Cerebrosides, Gangliosides
Fatty acid + Nitrogen Base + Phosphate + Sphingosine
Glycolipids = FA + NB + Sphingosine + Carbohydrates

3.Lipoproteins: Macromolecular Complexes of lipids with
proteins.
Ex : LDL, VLDL, HDL
4. Other complex lipids:
Sulfolipids, amino lipids and lipopolysaccharides are among the
other complex lipids.
DERIEVED LIPIDS:
They are the hydrolytic products of the first two groups of
lipides.
eg: fatty acids, steroids, alcohols, steroids, keton bodies, lipide
soluble vitamins

MISCELLANEOUS LIPIDS:
These include a large number of compounds possessing the
characteristics of lipids.
€.g., carotenoids, squalene,hydrocarbons such as pentacosane(in
bees wax), terpenes etc.
NEUTRAL LIPIDS :
The lipids which are uncharged referred to as neutral lipids.
These are mono-, di-, and triacylglycerols, cholesterol and
cholesteryl ester

• FUNCTIONS:
• They are concentrated fuel reserve of the body (TGL)
• Structural component of bio membrane (Phospho lipides /
cholesterol)
• Surfactants, detergent and emulsifying agents.
• Electric insulator in neurons.
• Lipides are important as cellular metabolism regulator's ( Steroid
hormones )
• Absorption of fat soluble vitamins like A,D,E,K
• Lipides protect internal organs serve as it gives shape and smooth
• appearance of the body

1.Phospholipids:
Phospholipids contain nitrogen base, alcohol, fatty acids , Glycerol
Phospholipids = po4 + NB + alcohol + FA+ Glycerol
Its are mainly two types
1. Glycerophospholipids
2. Sphingo phospholipids

Phospholipids, containing phosphoric acid.
1. Nitrogen containing glycerophospholipids:
Lecithin (Phosphatidyl choline)
Cephalin (Phosphatidyl Ethanolamine)
Phosphatidyl serine
2. Non-nitrogen glycerophospholipids:
Phosphatidyl inositol
Phosphatidyl glycerol
Di phosphatidyl glycerol
3. Plasmalogens, having long chain alcohol
Choline plasmalogen
Ethanolamine plasmalogen

2. Sphingolipids & sulfatides
1.Sulphated cerebrosides
2.Sulphated globosides
3.Sulphated gangliosides
Non-phosphorylated lipids (Glycolipids)
1. Glycosphingolipids
2.Cerebrosides
3. Globo sides
4. Gangliosides

Phosphatidic acid :
Glycerophospholipids contain they have esterified two fatty acids
on the first two carbons (usually SFA on C1 and UFA on C2) and
nitrogen base on carbon - 3
Fatty acid + glycerol + nitrogen base

1.Cephalin (phosphatidyl ethanolamine)
α,β form are esterified with phosphoric acid , the phosphate group is
attached with Ethanolamine
Witch play an important role in blood coagulation.

2.Lecithin (phosphatidyl choline) :
Nitrogen base contain phospholipids
α,β form are esterified with phosphoric acid , the phosphate group is
attached with choline.
Glycerol + Fatty acid + Nitrogen Base + Choline

Actions of phospholipase :
Phospholipases are the enzymes hydrolyse phospholipids
Phospholipase A2
Lecithin Lysolecithin + fatty acid
Phospholipase A1
Lecithin Acyl glycerophosphoryl
choline + fatty acid
Phospholipase C
Lecithin 1,2 diacyl glycerol
+ Phosphoryl choline
Phospholipase D
Lecithin Phosphatidic acid +
choline

Actions of phospholipase :
• Phospholipase A2 acts on an intact lecithin molecule hydrolyzing the fatty
acid esterified to the beta (second) carbon atom. The products are
Lysolecithin and fatty acid
• Lysolecithin is a detergent and hemolytic agent. The enzyme is present in
the venom of viper snakes. The hemolysis and consequent renal failure

Pulmonary surfactants
• Surfactant : Surfactant is surface active agent it prevent collapse of
the lungs .
• Pulmonary surfactant is surface active lipoprotein (Phospho
lipoproteins ) formed by alveolar cells. It contain both hydrophilic and
hydrophobic regions. The molecules seen in air – water interface of
alveoli.
• The hydrophilic head dips in water hydrophobic tail face towards the
air so that surface tension is reduced
• The pulmonary surfactant reduces surface tension at the air liquid
interface of the alveolus. This preventing it collapse during end
exhalation.

• The Haigh surface pressure resists a decrease in alveolar surface area
, will low surface tension stabilizes the lung by decreasing Pressure
gradient across the alveolar lining layer

Pulmonary surfactants
• Secreted by two types of cells
• Type II alveolar epithelial cells
• Clara cells.
Composition of surfactant :
it Lipoprotein complex it forms lipids & phospholipids , proteins ,
ions ..
DPPC: Dipalmitoylphosphotidyl choline – 40%
Other phospholipids – 40 %
Surfactant proteins - SP – A, SP-B, SP-C. SP-D – 5%
Other phospholipids – Phosphatidyl choline – 85%
Phosphatidyl glycerol – 10%

Clinical importance of surfactant
1.Respiratory distress syndrome (RDS)
2.Acute Respiratory distress syndrome (ARDS)
3.Meconium aspiration syndrome
4.Neonetal hyaline membrane disease (or)
Infant respiratory distress syndrome

1.Respiratory distress syndrome (RDS)
• It is due to a defect in the biosynthesis of dipalmitoyl lecithin (DPL), it is
main pulmonary surfactant. Premature infants have a higher incidence of
RDS because the immature lungs do not synthesize enough DPL.
• It is one of the most common causes of morbidity in preterm neonates.
The patient shortly after birth with apnea, cyanosis , nasal flaring , poor
feeding and tachypnea

2.Acute Respiratory distress syndrome (ARDS)
• Acute lung injury and syndrome of acute pulmonary inflation , its
characterised by sudden on set, impaired gas exchanges , and
pulmonary enema , the infections is the most common cause of
development of ARDS in children's at the age of 1year

Neonatal hyaline membrane disease (or)
Infant respiratory distress syndrome
• Histological it is called hyaline membrane disease.
• Hyaline membrane are seen lining the alveoli of lung , hyaline
membrane are composed of fibrine, caller debris , red blood cells
,neutrophils and macrophages.
• They are appearance as eosinophilic amorphous material. Ling or
filling the air spaces and blocking gas exchanges.
• Blood passing through lungs is unable to pick up oxygen and unload
Co2 this condition is called as neonatal respiratory distress
syndrome / respiratory distress syndrome of new born.
• It sis surfactant deficiency disorder . It is seen in premature infants
and is caused by insufficiency of pulmonary surfactant production.

• It can also result from a genetic problem with associated with
production of surfactant associated proteins.
• IRDS – affect about 1% new born infants and is the leading cause of
death in preterm infants.
• the pregnancies of greater than 30 weeks , the fetal lung maturity
may be tested by sampling the amount of surfactant in the amniotic
fluid.
• This including the lecithin – sphingomyelin ratio (L /S) and
phosphatidyl glycerol (PG) .
• If the L/S ratio is less than 2:1 the fetal lung may be surfactant
deficiency
• The presence of PG usually indicates fetal lung maturity .

Functions:
1.Involved in formation of cell membrane formation.
2.It act as surfactant.
3.Choline takes part in transmethylation reaction.
4.Choline plays a role in nerve impulse transmission as acetylcholine.
5.Choline act as lipoatrophic factor.
6.It helps cholesterol dissolved in bile.
7.Lecithin also act as components of cytochrome p450 system.

Phosphatidyl serine : Amino group of serine is present in this group of
glycerophospholipids
Fatty acid + glycerol + nitrogen base + serine

2. Non-nitrogen glycerophospholipids:
Phosphatidyl inositol
Phosphatidyl glycerol
Di phosphatidyl glycerol

• Phosphatidyl inositol:
Inositol attached to the phosphatidic acid to give phosphatidyl inositol
It is important compound from cellmembrane
It act as secondmessenger it mediate for hormonal action
Ex : Oxytocin , vasopressin.
Fatty acid + Glycerol+phosphate + inositol

Cardiolipins :
phosphatidyl glycerol, Di phosphatidyl glycerol.

Function :
1.Involved in formation of cell membrane and inner mitochondrial
membrane.
2.Essential for electron transport chain
3.Decreasing cardiolipins mitochondrial disfunction associated with
heart failure.
3.Hypothyroidism

Sphingo phospholipids
• Sphingomyelins
• Sphingomyelins are the only sphingolipid that contain phosphate and have no sugar moiety
• They are found in large quantities in nervous system. Different sphingomyelins may be formed
depending on the fatty acid attached.
• Common fatty acids found are—lignoceric (24 C), nervonic (24 C, one double bond) and cervonic
(22 C, 6 double bonds
• Because of its amphipathic nature sphingomyelin can act as an emulsifying agent and
detergent
• The relative proportion of lecithin and sphingomyelin is important in biological fluids like
bile, amniotic fluid,.
• Sphingomyelin combined with fatty acid is called ceramide, which is a component of
glycosphingolipids

• Non-phosphorylated lipids
• They are seen widely in nervous tissues. This group of lipids do not
contain phosphoric acid; instead they contain carbohydrates and
ceramide
1. Glycosphingolipids
2. Cerebrosides
3. Globo sides
4. Gangliosides

Glycosphingolipids or Glycolipids
1. Cerebrosides
Ceramide + Glucose - Glucocerebroside
Ceramide + Galactose – Galacto cerebroside
2.Globosides (Ceramide oligosaccharide)
They contain two or more hexoses or hexosamines, attached to
ceramide molecule
Ceramide + Galactose + Glucose – Lactosylceramide
3.Gangliosides :
They are formed when ceramide oligo-saccharides have at least one
molecule of NANA (N-acetyl neuraminic acid) (sialic acid) attached to them.

Ceramide + Glucose + Galactose + NANA – Gangliosides

Function of phospholipids
• It Form the structural components of membranes and regulate
membrane permeability.
• Phospholipids (lecithin, cephalin and cardiolipin)i n the mitochondria,
maintaining the conformation of ETC component.
• Absorption of fat from the intestine.
• Phospholipids participate in the reverse cholesterol transport and
help in the removal of cholesterol from the body.
• Dipalmitoyl phosphatidylcholine is an important Lung surfactant.
• Prevents Respiratory distress syndrome in infants.

• Cephline is an important group of phospholipids participante in Blood clotting.
• Phospholipids( phosphatidyl inositol ) are involved in signal transmission across
membranes.
• Arachidonic acid, an unsaturated fatty acid liberated from phospholipids, serves
as a precursor for the synthesis of eicosanoids (prostaglandins, prostacyclin’s.)

FATTY ACIDS
FATTY ACIDS CAN BE DEFINED AS CARBOXILIC ACID WITH
HYDROCARBON SIDE CHAIN. THIS IS THE SIMPLEST FORM OF
LIPUIDS
R – COOH
COOH – Carboxylic group
R – Hydrocarbon chain
Classification
1.number of carbon atoms
2.length of hydrocarbon side chain
3.nature of hydrocarbon side chain
4.Nomenclature of fatty acid

1.Number of carbon atoms mainly two types
A. Even chain carbon atoms
B. Odd chain carbon atoms
1.Even chain carbon atoms
They contain 2.4.6 carbon atoms sequential addition of
2 carbons
Ex: Acetic acid – CH3COOH
Butyric acid – CH3(CH2)2COOH
2. odd chain carbon atoms
It contain carbon atoms 3.5.9 add numbers
Ex: Propionic acid – CH3 CH2 COOH
Velluric acid - CH3(CH2)3 COOH

2.Depending up on length of carbon chain
1. According to chain length:
A. Short 2 - 6 carbons EX : Acetic acid CH3COOH
B. Medium 8 - 10 carbons EX : cupric acid CH3 (CH2)6 COOH
C .Long 16 - 24 carbons EX :Arachidonic acid
CH3 (CH2)4CH = CHCH2CH=CHCH2CH=CHCH2CH=CH(CH2)3COOH
3.Nature of hydrocarbon side chain
A .Saturate fatty acids
B. Unsaturated fatty acids
A .Saturate fatty acids
saturated fatty acids do not contain double bonds
Ex : Acetic acid – CH3COOH
B.UnSaturate fatty acids
Unsaturated fatty acids it contain double bonds

Mainly two types
1MUFA - Monounsaturated fatty acids
2.PUFA - Polyunsaturated fatty acids
1MUFA : it contain single double bound
Ex : Palmitoic acid – CH3 (CH2)CH = CH (CH2)7COOH
2.PUFA
It contain more than one double bound
Liolenic acid : CH3(CH2)CH = CHCH2CH = CH(CH2)7COOH

Unsaturated fatty acids They exhibit geometrical isomerism at the
double bonds.
All the naturally occurring fatty acids have the cis configuration.
Body during metabolism trans fatty acid are formed
Cis-form
(Oleic acid)
Trans-form
(Elaidic acid)
Unsaturated Fatty Acids
Textbook of Biochemistry for Medical Students, 9/e by DM Vasudevan, et al.
© Jaypee Brothers Medical Publishers

4.Nomenclature of fatty acid
The saturated fatty acids end with a suffix – anoic
Ex Common name Systemic name
Acetic acid Ethanoic acid
Butyric acid n-Butanoic acid
The Unsaturated fatty acids end with a suffix - enoic:
Ex : Common name Systemic name
Palmitoleic acid cis-9-Hexadecenoic acid
Oleic acid cis-9-Octadecenoic acid

Numbering of carbon atoms :
The carbon atoms of fatty acids are numbered as C1, C2 etc starting
from the COOH group.
Adjacent to the carboxyl group 2.3.4. starts from α,β,γ,δ.
starting from the methyl end, the carbon atoms may be numbered as
omega ()-1,2,3, etc
6 5 4 3 2 1
CH3 — CH2 — CH2 — CH2— CH2 — COOH
1 2 3 4 5
6 5 4 3 2 1
1 2 3 4 5

• Omega (ω) Classification of fatty acids:
Omega classification of fatty acid is used frequently in nutritional and
clinical practise.
The terminal carbon with the methyl group is counted as the first
carbon according to (ω) classification , the unsaturated fatty acid are
broadly divided into 3 groups
ω3 series - Linolenic acid
Timnodonic acid
ω6 series - Linoleic acid
Arachidonic acid
ω9 series - Oleic acid

Common No Chemical nature Occurrence
name carbon
atoms
Even chain, Saturated fatty acids
Acetic 2 Saturated; small chain Vinegar
Butyric 4 do Butter
Caproic 6 do Butter
Lauric 12 do Coconut oil
Palmitic 16 Saturated; long chain Body fat
Stearic 18 do do
Odd-chain fatty acids
Propionic 3 Saturated; Odd chain Metabolism

Unsaturated fatty acids
Common
name
No. of
carbon
atoms
Chemical nature Occurrence
Palmitoleic 16 Monounsaturated (w7) Body fat
Oleic 18 do (w9) do
Erucic 22 do (w9) Mustard oil
Nervonic 24 do (w9) Brain lipids
Linoleic 18 2 double bonds (w6) Vegetable oils
Linolenic 18 3 double bonds (w3) do
Arachidonic 20 4 double bonds (w6) Vegetable oils
Textbook of Biochemistry for Medical, 9/e by DM Vasudevan, et al.

• Polyunsaturated fatty acids :

1. Example, Linoleic and Linolenic acids
2. They are called essential fatty acids, because they cannot
be synthesized by the body and have to be supplied in the diet.
3. Unsaturated fatty acids are also designated as
4. ω3 (omega 3) family—
5. Linolenic acid ω6 family—
6. Linoleic and Arachidonic acids ω9
7. family—Oleic acid
8. Arachidonic acid is the precursor of prostaglandins. Arachidonic
acid can be synthesized in the body
Clinical Significance of PUFA

1.Arachidonic acid is the precursor of prostaglandins. Arachidonic acid can be
synthesized in the body.
2.The pentanoic acid present in fish oils is of great nutritional importance (ω3 unsaturated
fatty acid).
3.Eicosanoids (eicosa = twenty) are derived from 20 C arachidonic acid. They are polyenoic
fatty acids. They are precursors of prostaglandins.
• Positive roles for ω3 fatty acids
1.Infent development
2 .Prevent cancers
3.Prevent cardiovascular disease
4.Hypertention
5.Hyperlipidemia

• TFA are present in dairy products and in hydrogenated
edible oils.
• They are generally considered to be injurious to health.
• However, TFA are used in food industry as they increase the shelf
life of the fried food.
• Oils containing PUFA also have high content of TFA.
• Fast food preparations have a high TFA content.
• Trans fatty acids adversely affect composition of blood lipids
and lipoproteins, systemic inflammation, endothelial dysfunction,
insulin resistance, diabetes and adiposity.
Trans Fatty Acids (TFA)

Hydrogenation
Unsaturated fatty acids may be converted to the corresponding
saturated fatty acids by hydrogenation of the double bond.
(+)2H (+)2H (+)2H
Linolenic — Linoleic — Oleic — Stearic
Hydrogenation of oils can lead to solidification and saturation, e.g.
Vanaspathi.
Properties of Fatty Acids
Te xtbook of Biochemistry for Medical Students, 9/e by DM Vasudevan, et al.

Halogenation
When treated with iodine, the unsaturated fatty acids can take
up two halogen atoms, at each double bond.
For example,
Oleic acid + I2  Di-iodo oleic acid
The number of halogen atoms taken up will depend on the number
of double bonds and is an index of the degree of unsaturation.
Halogenation

The short and medium chain fatty acids are liquids, whereas
long chain fatty acids are solids at 25oC.
Melting and boiling points increase, with increase in chain length.
The unsaturated fatty acids have lower melting point compared to
saturated fatty acids with the same chain length.
Physical Characteristics / Melting point

Saturated and unsaturated fatty acids form salts with alkali.
CH3—COOH + NaOH  CH3—COONa
+ H2O
Sodium and potassium salts of long chain fatty acids are called
soaps. Which are of great importance of daily life.
To make sodium soaps usable as toilet soap.
Small amount of Sodium carbonate or silicate are added, this makes
soaps lather even in hard water.
Detergents of long chain fatty acids with quaternary ammonium or
salts of lauryl sulphuric acid , sulphate lauryl monoacylglycerol.
They are good wetting agents and emulsifiers and can lather equally
well in heard watter.
Salt Formation

Glycerol + fatty acid  Mono acyl glycerol
Monoglyceride + fatty acid  Di acyl glycerol
Diglyceride + fatty acid  Triglyceride
or tri acyl glycerol
or neutral fat
Ester Formation
When a PUFA is
present, it is esterified
to the 2nd or beta
carbon atom.

Essential fatty acid
• The fatty acids that cannot be synthesized by the body and, there fore,
should be supplied in the diet are known as essential fatty acids (EFA
• polyunsaturated fatty acids, namely
linoleic acid (18 : 2; 9, 12)
Iinolenic acid (18 : 3; 9, 12, 15).
Arachidonic acid
Biochemical functions of EFA
a. Essential fatty acids are required for the membrane structure
b. transport of cholesterol
c. formation of lipoproteins, prevention of fatty liver etc.
d. Another important group of compounds, namely eicosanoids

Deficiency of EFA:
The deficiency of EFA
results in phrynoderma or
toad skin,
on the posterior and lateral
parts of limbs, on the back
and buttocks, loss of hair
and poor wound healing

STERIODS
• Steroids are the compounds containing a cyclic steroid nucleus (or ring) namely
cyclopentanoperhydrophenanthrene (CPPP).
• It consists of a phenanthrene nucleus (rings A, B and C) to which a cyclopentane ring
(D) is attached
• The steroid nucleus represents saturated carbons, unless specifically shown as double
bonds.
• 19,18 Carbons are attached to the methyl side chain.
• Carbon 10,13 contains single bonds.
• Carbon 17 contain side cha are present

• There are several steroids in the biological system. These include cholesterol, bile
acids, vitamin D, sex hormones, adrenocortical hormones, sitosterol, cardiac
glycosides and alkaloids.

Structure of cholesterol
• Cholesterol Is Greek word (chole-bile)it first isolated from bile.
• Cholesterol exclusively found in animals, it most abundant animal
steroid.it weal distributed in cell membrane and lipoproteins.
• STRUCTURE OF CHOLESTEROL :
• Structure of cholesterol (C27 H46 O)
• It has only one hydroxyl group at C3. the double bound present
between C5 and C6
• The 8 carbon aliphatic side chain attached to the C17.methyl side
chain will present in 19-18
• Presence of –OH group cholesterol is weekly amphipathic in nature
• Cholesterol is found in association with fatty acid to form cholesterol
esters occur at the OH group of C3

Degradation of cholesterol
Functions of cholesterol:
1.Formation of cell membrane
2.synthesis of bile salts.
3.synthesis of steroid hormones
(mineralocorticoids , glucocorticoid, sex hormones )
4.synthesis of vitamin – D
5.Estrification
6.Nerve conduction

2.synthesis of steroid Hormones

2.synthesis of bile salts and bile pigments

4.synthesis of vitamin – D
Ergo calciferol vitamin -D2
Cholecalciferol – D3

• 6.Nerve conduction : cholesterol is main precursor for
formation of nerve fibres
• Cholesterol paly an important role transmission of electrical
impulse to the nerves tissues
• 7. Esterification (Energy)
• Cholesterol gives energy from β oxidation formation of
acetyl coA
• Conditions like During starvation, Diabetes mellitus ketone
bodies are major fuel source for Brain ,CNS

AMPHIPATHIC LIPIDS
(Amphi – Both) (Pathos – passion)
Amphipathic lipids can be defined as molecules witch contain both hydrophobic
(Non polar ) and hydrophilic ( Polar ) groups are known as amphipathic lipids.
EX :
Phospholipids
Glycolipids
Free fatty acids
Free cholesterol
Bile salts

• Fatty acids contain a hydrocarbon chain with a carboxyl (COO-) group at
physiological pH. The carboxyl group is polar in nature with affinity to water
(hydrophilic) while hydrocarbon chain of fatty acid is hydrophobic
6 5 4 3 2 1
1 2 3 4 5

• Phospholipids have hydrophilic head (phosphate group attached to choline,
ethanolamine, inositol ) and long polar hydrophobic tail

Amphipathic lipids their biological significance
When amphipathic lipides are
made soluble in water the
hydrophilic groups orient
themselves towards the
aqueous phase (water) , the
hydrophobic group stay away
from the aqueous phase.
leads to the formation of
micelles
Micelle formation, facilitated
by bile salts is very important
for lipid digestion and
absorption
Formation of membrane bilayer

TRIACYLGLYCEROL
• Triacylglycerols are the esters of glycerol with fatty acids.
• They are insoluble in water and non-polar in character and
commonly known as neutral fats.
FATS AS STORED FUEL :
• Primarily function as fuel reserves of animals.
• The fat reserve of normal humans (men 2O% and women 25%
by weight).
• sufficient to meet the body's caloric requirements for 2-3
months
FATS PRIMARILY OCCUR IN ADIPOSE TISSUE :
• Adipocytes of adipose tissue-
• Predominantly found in the subcutaneous layer and in the
abdominal cavity.

Why has fat been chosen as the energy reserve of the body
• The body stores in the form of triacylglycerol (TAG).
• (TAG) are highly concentrated store of energy because they are
reduced and anhydrous.
• TAG – produced energy 9 cal / g . Carbohydrates and proteins are
produced in 4cal / g
• TAG are non – polar and so they are stored in anhydrous form (free
form in water ) where as carbohydrates and proteins poler they are
highly hydrated)

STRUCTURES OF ACYLGLYCEROLS :
Mono , di and triacylglycerols, respectively consisting of one, two and
three Molecules of fatty acids esterified to a molecule of glycerol. Is
known as triglycerol

SIMPLE TRIACYLGLYCEROL
• all the three hydroxyl groups of the glycerol are esterified to
the same fatty acid
• e.g. Tripalmitin, Triolein, etc.
MIXED TRIACYLGLYCEROL
• Different fatty acids are esterified to the hydroxyl groups of
glycerol.
• e.g. 1, 3-dipalmitoyl-2-olein; 1-palmitoyl-2, 3-distearin, etc…

PHYSICAL PROPERTIES
• 1.HYDROLYSIS
• 2.SAPONIFICATION
• 3.RANCIDITY
• 4.ANTIOXIDENT

STORAGE OF FAT
• Stored in adipose tissue.
• When stored as triacylglycerol , water molecules are repelled
and space requirement is minimal.
HYDROLYSIS OF TRIACYLGLYCEROL

2.SAPONIFICATION
• Triglycerides are hydrolysed by alkali, the process is known as
saponification. products are glycerol and soaps.
TGL + 3 NaOH Glycerol + 3 R – COONa (soap)
3.RANCIDITY
Rancidity is the term used to represent the deterioration of fats
and oils resulting in the unpleasant taste.
Rancidity occurs when fat and oils are exposed to air, moisture,
light, bacteria

• It mainly two types
1.Hydrolytic rancidity
2.oxidative rancidity
1.Hydrolytic rancidity
Occurs due to partial hydrolysis of TGL by bacterial enzymes
2.oxidative rancidity
Is due to oxidation of unsaturated fatty acids this resulting formation of unpleasant
products such as dicarboxylic acid, aldehydes, ketons

Lipid peroxidation and antioxidant
Peroxidation of lipides occurs in when they are exposed to the air ,
moisture or bacteria , resulting in the deterioration of their nutritional
quality (rancidity) , rancidity fats are not suitable for consumption.
Peroxidation of lipids generate free radicals which are potentially
dangerous to the tissues.
The deterious effects of free radicals are controlled and they are
eliminated from biological system by some naturally occurring
substances in the body known as antioxidant , they include
Vitamin E, vitamin C , β carotene.

Tests to check purity and nutritional quality of foods
Reichert – Meissl number (RM number)
iodine number
acid number :

Reichert – Meissl number (RM number)
Rm number is defined as the amount of 0.1 N KOH required to
neutralise the volatile fatty acids distilled from 5 gr of fat.it is employed
to assess the purity of fats having more volatile fatty acid (C4.C6.C8)
Ex: butter the RM number of butter is between 25 and 30

IODINE NUMBER
• Number of grams of iodine taken up by 100 grams of fat. Iodine
number is used to asses the degree of unsaturation of fat. It is used
to check the purity and nutritive value of fat and oils.
the iodine number of a few common fats and oils

Acid number :
it is the number of KOH required to neutralise free fatty acids occurring
in 1gr of fat or oil. refined edible oils , when decomposed due to
(bacterial or chemical contamination ) release free fatty acids, so oils
with increased acid number are considered unsafe and non – edible.

• Lipoproteins are molecules complex that consisting of Lipid
and proteins
• The function is transportation of vehicle for lipid in blood
plasma, lipids delivery to the various tissues for utilization.
Classification of lipoproteins
1.Chylomicrons
2.VLDL (Very low-density lipoproteins )
3.LDL – (low-density lipoproteins )
4.HDL –(High density lipoproteins)
5.Albumin – Free fatty acids

1.Chylomicrons :
Chylomicrons are synthesized by intestine and trans port
exogenous TGL
It consisting of 99% of lipids and 1% in concentrated proteins
2.VLDL (Very low-density lipoproteins )
VLDL are synthesized by intestine and transport Endogenous TGL
3.LDL – (low-density lipoproteins )
It is also called as bad cholesterol
LDL is formed from the VLDL it transport the cholesterol from
liver to tissues
4.HDL –(High density lipoproteins)
It is also called as good cholesterol
HDL is synthesized In liver transportation of cholesterol from
tissue to liver

5.Albumin – Free fatty acids :
Fatty acids bound with albumin witch can trans port the 20 – 30% of free fatty acids
LIPD PROFILE
Test names Normal values
1.Cholesterol - 160 – 200 mg/dl
2.Tryglyceriods - up to 160 mg/dl
3.HDL - 30 – 60 mg/dl
4.LDL - 80 – 150 mg/dl
5.VLDL - 20 – 40 mg/dl

lipid chemistry 20-04-2022.pptx

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