Structural Lipids - Phospholipids, Glycolipids. Phospholipids types - Glycerophospholipids, Sphingolipids, and their importance in plant and animal cells. Examples for phospholipids and their structure. Sphingomyelin, ceramide, lecithin, cephalin.

2. STRUCTURAL LIPIDS
Phospholipids and glycolipids are important
structural lipids and are constituents of biological
membranes.

4. Phospholipids - Introduction
LIPIDS:
 Lipids are macrobiomolecule that are insoluble in water, but
soluble in organic solvents like ether, benzene, chloroform
etc.
PHOSPHOLIPIDS:
 Phospholipids are a class of lipids whose molecule has a
hydrophilic "head" and hydrophobic "tails".
 Phospholipids are compound lipids contain fatty acids,
alcohol, phosphoric acid and nitrogenous base.

6. Phospholipids - Structure

7. Phospholipids - Introduction
 Phospholipids are the major component of biological
membranes.
 Phospholipids are compound lipids contain fatty acids, alcohol,
phosphoric acid and nitrogenous base.
 There are two classes of phospholipids
Glycerophospholipids – contain glycerol as alcohol
Sphingophospholipids - contain sphingosine as alcohol

9. Phospholipids - Glycerophospholipids
 Glycerophospholipids are the major lipids that occur in biological
membranes.
 They contain glycerol, fatty acids, phosphoric acid and a
nitrogenous base.

10. Glycerophospholipids
o Glycerophospholipids are the major lipids that
occur in biological membranes.
o They contain glycerol, fatty acids, phosphoric
acid and a nitrogenous base.

11. The general formula of glycerophospholipids
is:

12. Glycerophospholipids
o Usually C-1 contans a saturated fatty acid
while C-2 contains an unsaturated fatty acid.
o The simplest of phospholipids is phosphatidic
acid.
o It contains a glycerol, fatty acids and
phosphate.

13. Phospholipids - Types
 Depending on the alcoholic residue attached, they are
named as:
 Phosphatidyl choline (lecithin),
 Phosphatidyl ethanolamine (cephalin),
 Phosphatidyl serine,
 Phosphatidyl inositol,
 Phosphatidyl glycerol and
 Diphosphatidyl glycerol (cardiolipin).

14. Phospholipids - Types
Lecithins are the most abundant group of
phospholipids in the cell membranes and have
metabolic and structural functions.
Dipalmitoyl lecithin is an important surface
active agent in lungs.

15. Phospholipids - Types

16. Phospholipids - Types
Cephalins are also membrane phospholipids and have the
base ethanolamine.
Phosphatidylinositol is involved in signal transduction.
Cardiolipin was first isolated from heart muscle. It
consists of two phosphatidic acid held by an additional
glycerol. It is an important component of inner
mitochondrial membrane.

17. Phospholipids - Types
Phosphatidylglycerol is a major phospholipid
in thylakoid membrane of chloroplast.
Phosphatidyl serine is a minor component of
most membranes. It is found to take part in cell
signaling and in apoptosis.

18. Phospholipids – Functions
In association with proteins, phospholipids form the
structural components of membranes and regulate
membrane permeability.
Phospholipids (lecithin, cephalin, and cardiolipin) in
the mitochondria are responsible for maintaining
the conformation of electron transport chain
components and thus cellular respiration.

19. Phospholipids – Functions
Due to their amphipathic nature, phospholipids can
combine with polar and non-polar compounds in the
cell.
Phospholipids participate in the absorption of fat from
the intestine.
Phospholipids are essential for the synthesis of
different lipoproteins and thus participate in the
transport of lipids.

20. Phospholipids – Functions
Arachidonic acid liberated from phospholipids
serves as a precursor for the synthesis of
eicosanoids (prostaglandins, prostacyclins,
thromboxanes, etc.)
Dipalmitoyl lecithin is an important lung
surfactant.
Cephalins participate in blood clotting.

21. Phospholipids – Functions
Phospholipids are essential components of bile
where they act as detergents and helps in
solubilization of cholesterol.
Phosphatidyl inositol is involved in signal
transmission across membranes.

22. Sphingophospholipids
Sphingophospholipids contain phosphate and
fatty acid attached to the alcohol, sphingosine
or its derivatives (dihydrosphingosine,
phytosphingosine).
 Eg: Sphingomyelins

23. Sphingophospholipids

24. Sphingophospholipids
The fatty acids are attached through an amide
linkage rather than the ester linkage.
The base present is normally choline.
Sugar residue may also be linked to phosphoric
acid group.

26. Sphingophospholipids
When fatty acid and sphingosine is linked by amide
bond, a ceramide is formed.
Ceramide is the fundamental unit in all
sphingolipids.
Sphingomyelins are found in large amount in the
brain and nerve tissues.
Sphingophospholipids are also found in the seeds
of several plant species.

27. GLYCOLIPIDS
Glycolipids contain an alcohol (sphingosine or
glycerol), fatty acid and a monosaccharide.
They are O-glycosides of either sphingosine or
glycerol derivative.
The commonly attached monosaccharides are D-
glucose, D-galactose or N-acetyl D-galactosamine.

29. GLYCOLIPIDS
Monogalactosyl diglycerides and
digalactosyldiglycerides have been shown to be
present in many higher plant tissues especially in
chloroplast membrane.
Glycolipids present in animal cells help in cell
to cell communication