Paper : 05 Metabolism of Lipids Module: 05 Types of Lipids I
Principal Investigator Dr. Sunil Kumar Khare, Professor, Department of Chemistry, IIT-Delhi
Paper Coordinator and Dr. Suaib Luqman, Scientist (CSIR-CIMAP) Content Writer & Assistant Professor (AcSIR) CSIR-CIMAP, Lucknow
Content Reviewer Prof. Prashant Mishra, Professor, Department of Biochemical Engineering and Biotechnology, IIT-Delhi
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METABOLISM OF LIPIDS Biochemistry Types of Lipids
DESCRIPTION OF MODULE
Subject Name Biochemistry
Paper Name 05 Metabolism of Lipids
Module Name/Title 05 Types of Lipids I
Dr. Vijaya Khader Dr. MC Varadaraj
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METABOLISM OF LIPIDS Biochemistry Types of Lipids
1. Objectives
To know how many types of lipids exist What are their significance How they act in a system
2. Concept Map
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METABOLISM OF LIPIDS Biochemistry Types of Lipids
3. Description
3.1 Types of Lipids I
According to BLOOR (1960), a German biochemist, lipids can be best understood under three categories
namely: Simple, Complex and Derived lipids.
Simple Lipids
Is a saponifiable lipid also known as storage lipid with two types of components i.e. alcohols with esters of fatty
acid.
1. Fats: Are glycerol with esters of fatty acids. Solid at room temperature due to saturation of
carbon atoms.
2. Oils: Are fats in the liquid state at room temperature due to unsaturation of carbon atoms.
3. Waxes: Are high molecular weight monohydric alcohols with esters of fatty acids.
i. True Waxes
ii. Esters of Cholesterol
iii. Esters of Vitamin A & D
Complex Lipids
Also known as conjugated or compound lipids are fatty acids esters with groups in toting up to a fatty acid and
an alcohol moeity. Being extensively distributed in animals, bacteria and plants, they are the major component
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METABOLISM OF LIPIDS Biochemistry Types of Lipids
of cell membranes and also found in circulating fluids. Complex lipids can be further sub divided into three
main subtypes:
1. Phospholipids: Lipids with a phosphate dreg, one glycerol, or an amino/fatty alcohol, with or without
one or two fatty chains (remarkably one inositol group, two phosphates or four fatty chains). They
frequently have bases with nitrogen and other substituents. In 1719, Hensing JT first reported the
occurrence of phosphorus in brain tissue followed by its extraction with ethanol discovered by
Vauquelin (1811). Later on alike substances were isolated from brain in alcohol (hot) which were
christened as acide cérébrique, cérébrote, matière blanche, or oleophosphoric acid. Gobley (1850),
isolated lecithin (synonymous phosphatidylcholine), a phosphorus-containing lipid from yolk of egg
(Greek: lecithos meaning egg yolk) and brain and designate it as lecithin. He also revealed that
glycerophosphoric acid may possibly be brewed from lecithin. Parallely, Strecker (1868)
demonstrated the presence of choline in bile. With the assistance of supportive findings, Gobley
anticipated lecithin structure including choline, margaric acid, oleic acid, phosphoglyceric acid. The
phospholipid chemistry made substantial advancement with Thudichum (1828-1901) who isolated
various phospholipid fractions and characterized them by means of their nitrogen/phosphorus ratio.
He depicted cephalin (synonymous phosphatidylethanolamine), discrete from lecithin by solubility
properties. From cephalin fraction, he also isolated ethanolamine and deemed it as a putrefaction
artifact of choline. In the Institute of Physiology and Chemistry in Strasbourg (France), Baumann &
Renall (1913) described ethanolamine phospholipids. Sphingomyelin (Greek: sphingein to bind
tight, myelos means marrow) was also isolated and described by Thudichum along with its
molecular constituents (fatty acid, sphingosine, choline, phosphoric acid). From the studies of
Thudichum, it has been concluded that phospholipids are the chemical soul of all bioplasm and 5
METABOLISM OF LIPIDS Biochemistry Types of Lipids
center of life. By 1927, sphingomyelin, lecithin and cephalin (well-defined phospholipids) had been
explained: followed by isolation of phosphatidic acid from cabbage leaves by Chibnall, one acetal
phosphatide (synonymous plasmalogen) from beef heart by Feulgen (1939),
phosphatidylethanolamine, phosphatidylserine and an inositol phospholipid (components of
cephalin) from brain by Folch (1942) and a diphosphoinositide (1949), cardiolipin from brain by
Pangborn (1944).
All through a protracted instance, phospholipids partition was supported on their solvent solubility.
Among his most renowned paper, Folch (1942) subjugated this idiosyncrasy to separate
ethanolamine, inositol and serine from brain cephalin. Thannhauser et al. (1936) demonstrated the
first appearance and use of a aluminum oxide column followed by the use of silica impregnated
paper in chromatography by Marinetti et al. (1956) and the use of TLC by Wagner et al. (1956) for
isolation, separation and characterization of phospholipids.
There are three categories of phospholipids.
i. Glycerophospholipids (synonymous Glycerophosphatides or Phosphoglycerides): a group for
the glycerol-containing phospholipids. It implies a few imitative of sn-glycero-3-phosphoric
acid that contains at least one O-alk-1'-enyl, O-alkyl, or O-acyl residue affixed to the glycerol
moiety with a polar head consist of a nitrogenous base, an inositol unit or a glycerol.
a. Phosphatidic acid: When hydrolyzed yield one equivalent of each of glycerol and
phosphoric acid.
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METABOLISM OF LIPIDS Biochemistry Types of Lipids
b. Lecithin: It contains fatty acid, phosphoric acid, glycerol and nitrogenous base choline.
c. Cephalin: It contains fatty acid, glycerol, phosphoric acid, nitrogenous base
ethanolamine (coalmine) or the amino acid serine.
d. Plasmalogens: On hydrolysis, it yields one mole each of aliphatic aldehyde, glycerol,
fatty acid, phosphoric acid and nitrogenous base ethanolamine or choline.
ii. Sphingophospholipids (synonymous Sphingosyl phosphatides or Phosphosphingolipids): a
group for the sphingosine-containing phospholipids. It contains a long chain base, glycoside
moiety with a phosphorus residue.
a. Sphingomyelin: It contains fatty acid, phosphoric acid and choline. Glycerol is absent.
iii. Alkylphosphocholines (phospholipid like molecules): a group for the esters of phosphocholine
with long chain aliphatic alcohols opposed in chain length, position and unsaturation of the cis-
double bond. Eibl et al., (1992) describes its remarkable biological and therapeutic activities
(Prog Exp Tumor Res 1992, 34, 1).
2. Glycolipids: Lipids with a glycosidic moiety (carbohydrates such as galactose or glucose), fatty acid,
sphingosine. Sometimes one or more phosphate groups are present. The long chain derivatives of
sugars restrain most frequently in bacteria and plants a glycerol (a diacylglycerol backbone) and in
animals (a ceramide backbone). A phosphorylated polysaccharide-lipid complex or a sterol may also
be found. Simple glycolipids are composed of a carbohydrate moiety linked to one fatty acid or fatty
alcohol. A wide variety of glycolipids are present in bacteria where specific glycopeptidolipids 7
METABOLISM OF LIPIDS Biochemistry Types of Lipids
or lipopolysaccharides are also available. Commensurate with the structure, glycolipids have the
following categories:
i. Glycerol based glycolipids: It contains mono or oligosaccharide moiety connected to the
glycerol (hydroxyl group), alkylated (or acylated) with one or two fatty acids. They might be
uncharged and referred as neutral glycoglycerolipids having a phosphate or a sulfate group.
Corresponding to their structure, glycerol based glycolipids can be sub-divided into the
following:
a. Neutral glycoglycerolipids
b. Glycophospholipids
c. Sulfoglycoglycerolipids
Neutral glycoglycerolipids
Most commonly this class contains one or two saccharide units allied glycosidically to
diacylglycerol or glycerol, however, neutral glycolipids with three or four sachharide units are
also reported. Being essential in algae, bacteria and higher plants, they are positioned in
photosynthetic membranes and are also present in minor amount in animals. About 85% of
neutral glycoglycerolipids (DGDG and MGDG) are present in photosynthetic membranes of all
oxygenic photosynthetic organisms. These glycolipids represent the most abundant lipid class
on Earth based on the innate loads of photosynthetic organisms. In Plasmodium falciparum (a
protozoan responsible for causing malaria), the discovery of a plastid without
galactoglycerolipids heaves the issue of trouncing the galactoglycerolipids during evolution. In
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METABOLISM OF LIPIDS Biochemistry Types of Lipids
a number of plants, galactosyl monoacylglycerol with a variety of galactose moieties has also
been uttered. There are two families of Neutral glycoglycerolipids.
Non-acylated glycoside moiety containing compounds
Acylated glycoside moiety containing compounds
Monogalactosyl diacylglycerol (MGDG) and digalactosyl diacylglycerol (DGDG)
Carter et al. (1956) stated the presence of Glycoglycerolipids in the wheat flour extracts
followed by its explicit alliance with tylakoid membranes of chloroplasts reported by Benson et
al. (1958) and their accurate structure was explicated by Carter et al. (1961). This stiff alliance
is epitomized by the algaecide or herbicide commotion of Galvestine (a MGDG synthase
inhibitor).
R1 and R2: Two fatty acid chains
Tri and tetragalactosyl diacylglycerols (superior homologues of galactolipids) were recognized
later in all plant tissues. Zhan et al. (2003) elucidated the structure of trigalactosyl
monolinolenylglycerol (a new glyceroglycolipid) isolated from Premna microphylla, a plant 9
METABOLISM OF LIPIDS Biochemistry Types of Lipids
used in Chinese folk medicine. A large amount of linolenic acid (18:3 n-3) and an explicit
trienoic acid (16:3 n-3) is present in both MGDG and DGDG. In higher plants, linolenic acid is
the lone fatty acid in MGDG and hence these plants are known as ‘18:3 plants’. In angiosperms,
16:3 n-3 is absent and linolenic acid is concerted in both sn 1 and sn 2 positions of both DGDG
and MGDG. Contrastingly, lower plants (conifers, ferns, mosses, green algae) and some
angiospermic families (Solanaceae, Chenopodiaceae, Brassicaceae) have 16:3 n-3 concerted in
the galactolipids at sn 2 position, whereas a short proportion of 18:3 n-3 is acylated at both
positions. These type of plants have a structural similarity with cyanobacteria and are referred to
as 16:3 plants. In photosynthetic diatoms and red algae, a high proportion of 20:5 n-3
galactolipids have been noted. Numerous fatty acids (n-3) have been dogged in MGDG isolated
from a brown alga (Sargassum thunbergii). In most fungi, glycosphingolipids is the main
glycolipidsand galactolipids have been found in small amounts. In MGDG, an unusual fatty acid
(18:3 n-1, ~25 %) was described from a marine diatom (Skeletonema costatum). They were
revealed to be metabolized into aldehydes (short chain), octadienal (8:2 n-4) and octatrienal (8:3
n-1) that could have lethal upshot on zooplankton crustaceans. Heptadienal (7:2 n-3), another
aldehyde was also known to be produced from eicosapentaenoic acid of MGDG.
Two linolenic acid (18:3 n-3) acyl groups containing MGDG have been depicted in fruits of
Rosa canina (rose hips) possessing anti-inflammatory properties (inhibits cell migration) which
unswervingly correlates to the anti arthritis activity of rose hip herbal remedies. Other reports
revealed anti tumor promoting properties, oxygen forage and virus counteracting activities of
galactosyl diglycerides from different sources. In Thailand, DGDG isolated from Clinacanthus
leaves demonstrated antiviral activity against herpes simplex virus. MGDG extracted from 10
METABOLISM OF LIPIDS Biochemistry Types of Lipids
Sargassum muticum, an invasive brown alga has been revealed to display inhibition of the
microbial growth including bacteria and fungi (anti-microfouling activity).
Specifics have shown that explicit galactolipids with 16:3 n-3 or 18:4 n-3 in the sn 1 position
and 20:5 n-3 or 18:5 n-3 in the sn 2 position is directly involved in cytotoxic reactions induced
by Phaeodactylum tricornutum, a marine diatom. It has also been discovered that Arabidopsis
chloroplasts enclose an arabidopside illustrated by the existence of 12-oxo-phytodienoic acid, a
phytohormone intimately allied to jasmonic acid acylated on glycerol carbon (sn 1), the 16:3 n-3
being acylated at sn 2 position. In MGDG, a 12/10 carbon oxoacids have been noticed in
Arabidopsis leaves linked to six carbon aldehydes, alcohols and their esters production which
are recognized as volatiles of leaf.
In the leaves of Linum usitatissimum, a novel family of oxylipin named Linolipins containing
MGDG has been exposed. Esterified residues (one or two) of divinyl ether-etherolenic acid and
parallel oxylipin comprising DGDG have also been alienated from the flax leaves damaged by
freezing-thawing or inoculated with phytopathogenic bacteria.
In Petunia hybrid flower, it has been observed that DGDG synthesis increases and the pistils-
pollinic tubes include elevated quantity than any other floral organs. In bacteria, sn 3-O-
glycosyldiacylglycerols possess glycoside moiety: a-D-mannopyranosyl (1->3)-O-D-
mannopyranoside (Micrococcus), a-D-galactopyranosyl (1->2)-O-a-D-glucopyranoside
(Lactobacillus), a-D-glucopyranoside (Pneumococcus, Staphylococcus), a-D-glucopyranosyl (1-
>2)-O-a-D-glucopyranoside and b-D-galactofuranoside (Mycoplasma), b-D-glucopyranosyl (1-
>6)-O-b-D-glucopyranoside (gentobiosyldiacylglycerol, Staphylococcus). In Propionibacterium
propionicum, a novel glycoglycerolipid (a-D-glucopyranoside (1->3) a-D-glucopyranoside) 11
METABOLISM OF LIPIDS Biochemistry Types of Lipids
enclosing an ether-linked alkyl chain at C-3 position of glycerol has been illustrated. Manca et
al. (1992), isolated a diglucosyl diglyceride with an incredibly exceptional diglucosyl structure
(1->4) from Thermotoga maritima.
Inquisitively, two moles of palmitic acid esterifies the glycerol moiety and acylated on the 6-OH
of the terminal glucose by one molecule of decanoic acid. It has been well-known that the
glycolipids present in flour act as surfactants and affect the texture, staling and volume of bread.
Selmair et al. (2008, 2010) reviewed the role of glycolipids in breadmaking and have shown that
monoalactosylglyceride and its lyso derivative perk up the baking performance of wheat flour.
Hamberg (1998) reported DGDG mono estolides in the kernels of oat.
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METABOLISM OF LIPIDS Biochemistry Types of Lipids
4. Summary
In this lecture we learnt about:
The Types of Lipids (Simple & Complex)
Importance of Phospholipids and Glycolipids
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METABOLISM OF LIPIDS Biochemistry Types of Lipids