CL-03:
COMPOUND LIPIDS
By
Santhosh Kumar. N
Assistant Professor
Dept. of Biochemistry
SIMS&RH, Tumkur,

Phospholipids Glycolipids Lipoproteins

PHOSPHOLIPIDS
• Esters of fatty acids containing Phosphoric acid group, nitrogenous bases and
other substitution groups.
G
L
Y
C
E
R
O
L
FATTY ACID
FATTY ACID
Phosphoric acid Nitrogenous Base
Amphipathic nature

Polar head
Hydrophilic region
Non polar Tails,
Hydrophobic region

G
L
Y
C
E
R
O
P
H
O
S
P
H
O
L
I
P
I
D
S
S
P
H
I
N
G
O
P
H
O
S
P
H
O
L
I
P
I
D
S
Phospholipids
It may be classified into 2
types based on the type of
alcohol

Glycerophospholipids / Phosphoglycerides
 Phospholipids containing alcohol as Glycerol -‘Glycerophospho-
lipids’.

•It does not occur in the tissues.
•It is an intermediate in the synthesis of TG &
phospholipids.

Glycerophospholipids
Lecithin ( Phosphatidyl choline)
Cephalin ( phosphatidylethanolamine)
Phosphatidyl inositol
Phosphatidylserine
Cardiolipin (Phosphatidyl glycerol)
Plasmalogens

Lecithin ( Phosphatidyl choline)
 Most abundant phospholipid in the cell membranes.
 Containing labile CH3 groups involved in methylation reactions.
 Storage form of choline in body
 Act as lipotropic factor & anti-cholesterol agent
O
O
H2C O C R
O
R C O CH
H2C O P O CH
2 CH2 N
+
CH3
CH3
CH3
O_
Phosphatidic Acid Choline
Nitrogenous bases

Lecithin ( Phosphatidylcholine)
Dipalmitoyl lecithin
Lysolecithin
 Found in lungs & secreted by
pulmonary type-II epithelial cells.
 Lung surfactant
 Defect leads to Acute pulmonary
respiratory distress syndrome in
infants.
-It formed by removal of the FA
either at C1 or C2 of lecithin
-Component of cobra venom & a
strong hemolysing agent.

Dipalmitoyllecithin found in the ECF
and surrounds the alveoli of the lungs
To prevent lung collapse during
breathing
It decreases the surface tension of
the lungs
In premature infant
Due to immature lungs,
Dipalmitoyllecithin do not syn enough
Collapse of the alveoli of lungs
Role of Dipalmitoyl lecithin (lungs surfactant)
Decreased oxygenation of blood &
tachypnoea (abnormal rapid breathing)
In normal conditions Respiratory distress syndrome

Lecithin / Sphingomyelin (L/S) ratio
 L/S ratio is a test of fetal amniotic fluid to assess for fetal lung immaturity
 A ratio of 2.0 or above is evidence of pulmonary maturity.
 Less than 2.0 is indicate immature fetal lung development
 Administration of natural or synthetic surfactant is used in the prevention
and treatment of respiratory distress syndrome

Cephalin (phosphatidylethanolamine)
• Involved in blood clotting process
• Thromboplastin coagulation factor –III, needed to initiate the clotting process
• Which catalyze the formation of thrombin from prothrombin
Ethanolamine
Nitrogenous base

Phosphatidylinositol
• The myoinositol is attached to phosphatidic acid to form PI
• Important constituent of the cell membranes
• Act as second messenger, on stimulation by for oxytocin &vasopressin.
• It helps in the release of calcium.
O P
O
O
H2C
CH
H2C
O
C
R1
O O C
O
R2
OH
H
OH
H
H
OH
H
OH
H
O
H OH
phosphatidyl-
inositol

Phosphatidylserine
• Component of the cell membrane & occurs in brain & RBCs
• Plays a key role in cell cycle signaling
• Act as a signal for macrophages to engulf the cells
serine

Phosphatidylglycerol (Cardiolipins)
• First isolated from cardiac muscle
• Imp component of inner mitochondrial membrane & involved in cellular
respiration.
• Act as an Antigenic properties.

Plasmalogens
• Found in bio-membranes of brain & muscles.
• Phospholipids having α, β unsaturated FA in ether linkage with the first OH-
group of glycerol
• The second OH group is esterified to a fatty acid
• The phosphoric acid is attached to choline or ethanolamine.

Platelet activating factor
- It synthesized by basophiles & stimulates platelet aggregation
- C1 of glycerol -ether linked alkyl chain & C2 is ester linked to acetic acid
- Helps to release of serotonin from platelets
- Involved in inflammation and allergic responses

SPHINGO
PHOSPHOLIPIDS
Alcohol as a sphingosine in phospholipids
Rich in Myelin sheath of nerve cell

Ceramide:
Amide group of sphingol is attached to carboxylic group of fatty acid
Sphingomyelin

Functions of Sphingomyelin
• Structural lipids of membranes of nerve tissues
• Regulates enzyme systems like protein kinase & protein phosphatase
• Protects neural fibres of CNS & myelin sheath

GLYCEROPHOSPHOLIPIDS (glycerol as alcohol)
Phosphatidyl choline Act as Lipotropic factor & lung surfactant
Phosphatidyl ethanolamine Participating in blood clotting process.
Phosphatidyl inositol (PI) Act as second messenger & release of calcium
Phosphatidyl serine Major component of the cell membrane
Plasmalogens /
Platelet activating factor
Stimulates platelet aggregation. Inflammation
and allergic reactions.
Cardiolipin Involved in cellular respiration
SPINGOPHOSPHOLIPIDS (sphingosine as alcohol)
Sphingomyelin Protects neural fibres of CNS & myelin sheath

GLYCOLIPIDS

• Glycolipids they do not contain phosphate.
• Essential components of cells, plasma membranes (outer leaflet) &
also most abundant in nervous tissues
Glycolipids
Cerebrosides
Sulfatides
Globosides
Gangliosides
Ceramide Carbohydrate
Glycolipids
Ceramide + Monosaccharides
Ceramide + Oligosaccharides
Ceramide + Monosaccharides + Sulfate
Ceramide + Oligosaccharides + Sialic acid

CEREBROSIDES
• High conc in white matter of brain & Myelin sheaths of nerves.
• Based on the type of fatty acids they are 4 types
Ceramide + Monosaccharides
Types of cerebrosides Fatty acid
Kerasine Lignoceric acid
Cerebron Cerebronic acid
Nervon Nervonic acid
Oxynervon Hydroxy derivatives of Nervonic acid

 Simplest glycolipids –
 Gluco-cerebrosides(Ceramide + Glucose)
 Galacto-cerebrosides(Ceramide + Galactose)
• It provide protective coating to each nerve and act as insulator

Gangliosides
• Imp Gangliosides present in the brain - GM1, GM2, GM3, GD & GT.
(G – Gangliosides, While, M- mono, D- di & T- tri sialic acid residues & numbering is
based on its relative mobility in electrophoresis).
• Simplest gangliosides found in tissue is GM3 (mono-sialo-di-hexosyl-
ganglioside)
Ceramide + Oligosaccharides + Sialic acid

Functions of Glycolipids
Involved in cell membrane receptors for certain
polypeptide hormones
Cell interactions, growth &
development
Act as an Antigenic property
(e.g., blood group antigens)
Mediating cell-cell recognition

LIPOPROTEINS

Protein
Lipid
Apoprotein
Lipoprotein
•Lipoproteins composed of triglyceride and cholesterol ester core &
surrounded by single lipid layer containing phospholipid and free
cholesterol & a shell of proteins.

CLASSIFICATION
According to their physical & chemical properties
Based on the density:
Separated by ultracentrifugation into 4 types
• Chylomicrons
• Very low density lipoproteins (VLDL)
• Low density lipoproteins (LDL) & IDL
• High density lipoproteins (HDL) – HDL-1, 2 & 3

Based on the electrophoretic mobility
In origin – chylomicrons
Migrating into β-globulin region – β-lipoprotein (LDL)
pre-β-globulin region –pre -β-lipoprotein (VLDL)
α-globulin region – α-lipoproteins (HDL)

Lipoprotein class Density (g/mL) Diameter
(nm)
Protein % Phospholipid % TG %
Chylomicrons < 0.95 100 - 500 1 – 2 7 84
VLDL 0.95 – 1.006 30 - 80 10 18 50
LDL 1.019 – 1.063 18 – 28 25 21 4
IDL 1.006-1.019 25 - 50 18 22 31
HDL 1.063-1.21 5 – 15 33 29 8
Composition lipoproteins

Families Chylomicrons LDL VLDL HDL
Lp-A A-I & II ---- ---- A-I & II
Lp-B Apo-B48 Apo-B48 Apo-B100 ---
Lp-C C-I, II, III C-I, II III C-I, II, III C-I, II, III
Lp-D --- -- -- HDL -3
Lp-E Apo-E Apo-E Apo-E Apo-E
Apolipoproteins
Major protein components of lipoproteins - Apo-proteins
These are classified by (A, B, C, D & E)
Sub groups given in roman numeral depending on the emerge from a
chromatographic column.

Apoprotein Functions
A-I In plasma; activates LCAT
A-II Enhances hepatic lipase activity
B-48 & B-100 Binds to LDL receptor
C-I Activate LCAT
C-II Activates lipoprotein lipase
C-III Inhibits lipoprotein lipase
D Also called as cholesterol ester transfer protein (CETP)
E Binds to LDL receptor

Functions of Apo-lipoprotein:
• Maintaining the structural integrity of the lipoproteins
• Responsible for recognition of particle by receptors
• Regulating certain enzymes, which act on the lipoproteins

FUNCTIONS OF LIPOPROTEINS
Chylomicrons Transport of dietary triglyceride and cholesterol esters from
intestine to peripheral tissues and liver.
Very low density
lipoprotein (VLDL)
Transports endogenous triglyceride from liver to peripheral
tissues.
low density
lipoprotein (LDL)
- It transports cholesterol from the liver to the peripheral tissues,
for use to form steroid hormones and building cell membranes.
- But it favors the deposition of cholesterol in arterial walls and to
play a role in disease of the blood vessels and heart.
- It increased risk for myocardial infarction - Bad cholesterol
HDL: - It transports free cholesterol from the peripheral tissue to the
liver, for using in energy metabolism, membrane reconstruction
and hormone function.
- HDLs also appear to prevent cholesterol from invading and
settling in the walls of arteries.
- It is an anti atherogenic agent.- Good Cholesterol

Next class –CL 04: Derived lipids