PRESENTED BY: AYESHA KABEER FROM: UNIVERSITY OF GUJRAT SIALKOT SUBCAMPUS 1. PHOSPHOLIPIDS 2. GLYCEROPHOSPHOLIPIDS 3. SPHINGOMYELIN 4. GLYCOLIPIDS

1. Phospholipids,
Glycerophospholipids,
Sphingomyelin,
Glycolipids
PRESENTED BY: AYESHA KABEER

2. Phospholipids are:
• major constituents of all cell membranes
• components of bile
• anchor some proteins in membranes
• signal mediators
• components of lipoproteins

3. Structure of phospholipids
• Phospholipids have two fatty acids that help form a diacylglycerol.The third
carbon of the glycerol backbone is also occupied by a modified phosphate
group However, just a phosphate group attached to a diacylglycerol does
not qualify as a phospholipid.This would be considered a phosphatidate or
phosphatidic acid (diacylglycerol 3-phosphate), the precursor to
phospholipids.To qualify as a phospholipid, the phosphate group should be
modified by an alcohol. Phosphatidylcholine and phosphatidylserine are
examples of two important phospholipids that are found in plasma
membranes.

4. Phospholipid

5. Properties of phospholipids
• Phospholipids are amphipathic molecules
• Head group = alcohol attached via phosphodiester linkage
to either:
• diacylglycerol (glycerophospholipid) or
• sphingosine (sphingophospholipid = sphingomyelin).

6. Cellular membranes are composed of phospholipids and sphingolipids
• Glycerophospholipids and sphingolipids spontaneously self-associate
in water to form bilayer vesicles (i.e., closed membranes)
• Bilayers are permeability barriers that enclose cells and cell organelles,
and “dissolve” intrinsic membrane proteins

7. Glycerophospholipids
• Glycerophospholipids are the main class of phospholipids
• They are the main lipid component of cell membranes, and
are important in the cell’s semipermeability
• They also interact with triacylglycerols and cholesterol to
increase their solubility in the blood
• These abilities of glycerophospholipids are due to their
amphipathic nature, with a polar head group and nonpolar
tails
Glycerol
PO4
Amino
alcohol
Fatty acid
Fatty acid

8. • Glycerophospholipids are similar to triacylglycerols, but have one ester
bond replaced with an amino alcohol phosphate ester.i.e.
Glycerophospholipid

9. Each
glycerophospholipid
includes
a polar region:
glycerol, carbonyl O
of fatty acids, Pi, & the
polar head group (X)
non-polar hydrocarbon
tails of fatty acids (R1, R2).
O P O
O
O
H2C
CH
H2C
OCR1
O O C
O
R2
X
glycerophospholipid
polar
non-polar
"kink" due to
double bond

10. Structure of a Glycerophospholipid

11. Lecithins and Cephalins
• Glycerophospholipids can be classified based on the amino alcohol
group
• Two common types are lecithins (which contain choline) and
cephalins (which contain ethanolamine)
• Lecithins and cephalins are highly abundant in brain and nerve
tissues, and are also found in egg yolks, wheat germ and yeast

12. Phosphatidylinositol, with inositol as polar head
group, is one glycerophospholipid.
In addition to being a membrane lipid,
phosphatidylinositol has roles in cell signaling.
O P
O
O
H2C
CH
H2C
OCR1
O O C
O
R2
OH
H
OH
H
H
OHH
OH
H
O
H OH
phosphatidyl-
inositol

13. The other one is cardiolipin. Cardiolipin is
found in mitochondrial membrane.

14. Sphingomyelin
• Sphingomyelins are phospholipids that are based on the 18-
carbon amino alcohol sphingosine, instead of on glycerol
• A fatty acid is linked to the amine group by an amide bond, and
an amino alcohol phosphate ester is linked to the bottom
hydroxyl group (the top hydroxyl group remains free)
• Sphingomyelin is the main component of the myelin sheath of
nerve cells

15. H2C
H
C
OH
CH
NH CH
C
CH2
CH3
H
OH
( )12
C
R
O
ceramide
H2C
H
C
OH
CH
N+ CH
C
CH2
CH3
H
H3
OH
( )12
sphingosine
In the more complex sphingolipids, a
polar “head group" is esterified to the
terminal hydroxyl of the sphingosine
moiety of the ceramide.
The amino group of sphingosine can
form an amide bond with a fatty acid
carboxyl, to yield a ceramide.

16. Sphingomyelin, with a phosphocholine head group, is
similar in size and shape to the glycerophospholipid
phosphatidyl choline.
Sphingomyelin has
a phosphocholine or
phosphethanolamine
head group.
Sphingomyelins are
common constituent
of plasma
membranes.
H2C
H
C
O
CH
NH CH
C
CH2
CH3
H
OH
( )12
C
R
O
PO O
O
H2
C
H2
CN+
CH3
H3C
CH3
Sphingomyelin
phosphocholine
sphingosine
fatty acid


17. Glycolipids(glycosphingolipids)
• Glycolipids are sphingolipids that have one or more
monosaccharides linked by glycosidic bonds to the bottom
hydroxyl of the sphingosine.
• In contrast to sphingomyelin they do not have a
phosphocholine group.

18. Types of Glycolipids(glycosphingolipids)
• Cerebrosides have a single monosaccharide (usually galactose)
- they are usually present at the cell surface, and are involved in
cellular recognition and immunity

19. Types of Glycolipids(glycosphingolipids)
• Gangliosides have two or more monosaccharides, usually
glucose and galactose
- they are abundant in the cell membranes of neurons
- they act at the cell surface as receptors for hormones

20. Functions of glycolipids