Structural Lipids: Specifically in reference to the plant world

1. DR. VIBHA KHANNA
Asso. Prof. (Botany)
SPC GOVERNMENT COLLEGE
AJMER (Rajasthan)

2. PLANT BIOCHEMISTRY
• BLOCK 1. : Lipid metabolism
– PRESENTATION 1: Structure and function of lipids,

3. LIPIDS
• Term first used by German biochemist Bloor in 1943.
• The word lipid is derived from a Greek word “lipos” which means Fat.
• They are:
1. Insoluble in water.
2. Soluble in non-polar organic solvents e.g. ether, acetone.
3. Contain carbon, hydrogen and oxygen sometimes contain nitrogen and phosphorous.
4. Neutral lipids upon hydrolysis yield glycerol and fatty acids*.
5. Take part in plant and animal metabolism.
6. In aqueous environment lipid molecules associate by non – covalent interactions to
form supramolecular structures such as monolayers,micelles,bilayers,and vesicles.

4. • FATTY ACIDS*
• Fatty acids are a class of compounds
containing a long hydrophobic
hydrocarbon chain and a terminal
carboxylate group.
• Fatty acid are long chain organic
acids usually from 4 to 30 carbon
atoms.
• Fatty acid which occur in natural fats
are usually monocarboxylic and
contain even number of carbon
atoms as these synthesized from two
carbon units.
• The chain may be saturated or
unsaturated.
• Some fatty acid have hydroxyl group
in the chain and still other may
possess ring structure

5. CLASSIFICATION OF LIPIDS:
On the basis of Structure

6. CLASSIFICATION OF LIPIDS :
On the basis of Functions
LIPIDS
STORAGE
LIPIDS
MEMBRANE
LIPIDS
CELL
SIGNALLING

7. MEMBRANE LIPIDS:
• All living cells are enclosed in
membrane.
• These membrane define the
inner and outer boundary of the
cells and also the
compartmentalisation of
different organelles within the
cell.
• The biological membrane
consists of a double layer of lipids
and the proteins.
• Lipid are hydrophobic in nature
they provide effective barrier to
polar molecules.
• Variety of lipid are known to be
present in biological membrane.

8. MEMBRANE LIPIDS
PHOSPHOLIPIDS
Phosphoglycereids
Phosphoinositides
Phosphosphingosides.
GLYCOLIPIDS
Glycosphingolipids
and
Glycoglycerolipids
CHOLESTROL

9. PHOSPHOLIPID:
• Phospholipid are the most abundant
membrane lipid.
• They serve primarily as structural
components of membrane and are never
stored in large quantities.
• Phospholipids consist of a glycerol molecule,
two fatty acids, and a phosphate group that is
modified by an alcohol.
• They are amphipathic.
– The phosphate group is the
negatively-charged polar head,
which is hydrophilic.
– The fatty acid chains are the
uncharged, nonpolar tails, which
are hydrophobic.
• Phospholipid are compound lipid and are
of three types;
1. Phosphoglycereids
2. Phosphoinositides
3. Phosphosphingosides.

10. PHOSPHOLIPID: Phosphoglycereids
• Phosphoglycerides have three parts:
– a three-carbon backbone of glycerol,
– two long-chain fatty acids esterified (or attached via an ether link in
Archaea) to hydroxyl groups on carbons 1 and 2 (C1 and C2) of the
glycerol and
– a highly polar or charged group ( like phosphoric acid) esterified to
the C3 hydroxyl group of glycerol.
• Lecithin is a phospholipid which consists of glycerol, two fatty acids, a
phosphate group and choline. (Lecithins are widely distributed in
nature, including various oil seeds like soybean and the yeasts .)
• Cephalins contain the amino alcohols serine or ethanolamine(in place
of choline). (Cephalins are found in most cell membranes, in animal
world. They have been identified from soybean oil.)

11. PHOSPHOLIPID: Phosphoinositides
• Phosphatidylinositol is an acidic (anionic) phospholipid that basically,
consists of a phosphatidic acid backbone, linked via the phosphate
group to inositol (hexahydroxycyclohexane).
• Phosphoinositides are the phosphorylated derivatives of
phosphatidylinositol.
• They have three parts:
– a three-carbon backbone of glycerol,
– two long-chain fatty acids esterified to hydroxyl groups on carbons 1 and 2
(C1 and C2) of the glycerol and
– attached to a polar head group (the cyclic hexahydroxy alcohol called
inositol) that extends into the cytoplasm. [The inositol is present as the
stereoisomer, myo-inositol.]
• Examples: phosphatidylinositol 3,4,5-trisphosphate, often called PIP3 ;
phosphatidylinositol 4,5-bisphosphate, often called PIP2
• *Phosphosphingosides: apparently lack in plants and the
microorganisms.

12. GLYCOLIPID
• Glycolipid is a structural lipid.
They are made up of lipids and
carbohydrate.
• It consists of a hydrophobic lipid
tail and one or more hydrophilic
sugar groups linked by a
glycosidic bond.
• Glycolipids are components of
cellular membranes
• They are generally found on the
extracellular face of eukaryotic
cellular membrane.
• They are also present on the
cell surface of some viruses,
bacteria.

13. GLYCOLIPIDS
• The basic structure of a
glycolipid consists of a mono- or
oligosaccharide group attached
to a sphingolipid or a glycerol
group, which can be acetylated
or alkylated, with one or two
fatty acids.
• These make up the two classes
– Glycosphingolipids and
– Glycoglycerolipids
• Glycolipids interact and bind to
the lipid-bilayer through the
hydrophobic nature of the lipid
tail which anchors it to the
surface of the plasma
membrane.

14. Cholesterol
• Cholesterol is a steroid derivative
and is present as membrane lipid in
almost all animal membranes.
• Derivatives of steroids, however, are
also found in plants, fungi, and
some bacteria.
• Cholesterol is a lipid with a
unique structure consisting of four
linked hydrocarbon rings forming
the bulky steroid structure. There is
a hydrocarbon tail linked to one end
of the steroid and a hydroxyl group
linked to the other end.
• The steroid nucleus consist of four
rings numbered A,B,C,D. the first
three rings have 6 carbons whereas
the fourth has only 5 carbons.

15. REFERENCES:
Biochemistry And Molecular Biology Of Plants
: Buchanan, Gruissem, Jones
Plant Physiology : Mohr