Biochemistry

1. Moazzam Ali Shahid
Senior Lecturer (Molecular Medicine)
Senior Research Officer (Research)
PhD Scholar (Biochemistry)

3.  Esters of fatty acids containing groups in addition
to an alcohol and a fatty acid.
1-PHOSPHOLIPIDS:
A-glycerophospholipids the alcohol is glycerol
B-sphingophospholipids the alcohol is sphingosine.
Example Plasmalogens: They are highly abundant in the
neuronal, immune, and cardiovascular cell membranes.
.Phosphatidylcholine

5.  A lecithin
CH2
CH
CH2
O
O
O
O
O P OCH2 CH2 N( CH3) 3
O
O-
+
palmitic acid
stearic acid
glycerol
choline

6.  Lecithin is a mixture of fats that are essential to
cells in the human body. It can be found in many
foods, including soybeans and egg yolks.

7.  Hydrophobic or hydrophilic?
◦ fatty acid tails = hydrophobic
◦ PO4 = hydrophilic head
◦ dual “personality”
interaction with H2O is
complex & very important!

8.  Hydrophilic heads attracted to H2O
 Hydrophobic tails “hide” from H2O
◦ can self-assemble into “bubbles”
 bubble = “micelle”
 can also form bilayer
bilayer

9.  Phospholipids create a barrier in water
◦ define outside vs. inside
◦ cell membranes

12. C OH
H
CH2OH
CH2OH
glycerol
Glycerophospholipids
(phosphoglycerides), are
common constituents of cellular
membranes.
They have a glycerol backbone.
Hydroxyls at C1 & C2 are
esterified to fatty acids.
An ester forms when a
hydroxyl reacts with a
carboxylic acid, with
loss of H2O.
Formation of an ester:
O O
R'OH + HO-C-R" R'-O-C-R'' + H2O

13. In phosphatidate:
 fatty acids are esterified to hydroxyls on C1 &
C2
 the C3 hydroxyl is esterified to Pi.
O P O
O
O
H2C
CH
H2C
O
C
R1
O O C
O
R2
phosphatidate

14. O P O
O
O
H2C
CH
H2C
O
C
R1
O O C
O
R2
X
glycerophospholipid
In most glycerophospholipids
(phosphoglycerides),
Pi is in turn esterified to OH of a polar head
group (X): e.g., serine, choline, ethanolamine,

18.  Sphingosine is formed by an amino alcohol head
group, with two hydroxyls, and one amino group
attached to a long unsaturated hydrocarbon
chain of typically 18 carbon atoms
H2C
H
C
OH
CH
N+ CH
C
CH2
CH3
H
H3
OH
( )12
sphingosine

22.  Glycolipid: a compound in which a carbohydrate
is bound to an -OH of the lipid
◦ many glycolipids are derived from ceramides
O
( CH2 ) 12 CH3
HO
NHCR
O
O
H
HO
H
HO
H
H
OH
H
OH
a-glucoside
bond
a unit of
-D-glucopyranose

23. Cerebrosides and gangliosides, collectively called glycosphingolipids, are
commonly found in the outer leaflet of the plasma membrane bilayer, with
their sugar chains extending out from the cell surface.
cerebroside with
-galactose head group
H2C
H
C CH
NH CH
C
CH2
CH3
OH
C
R
O
OH O
H H
H
OH
H
OH
CH2OH
H
O
H
( )12
• A cerebroside is a
sphingolipid (ceramide)
with a monosaccharide
such as glucose or
galactose as polar head
group.
• A ganglioside is a ceramide
with a polar head group
that is a complex
oligosaccharide, including
the acidic sugar derivative
sialic acid.

24.  Sphingomyelins have phosphocholine or phosp
hoethanolamine molecule with an ester
linkage to the 1-hydroxy group of a ceramide.

26. OH
( CH2 ) 12 CH3
HO
NH2
Sphingosine
OH
( CH2 ) 12 CH3
HO
NHCR
A ceramide
(an N-acylsphingosine)
OPOCH2 CH2 N( CH3 ) 3
( CH2 ) 12 CH3
HO
NHCR
A sphingomyelin
O
O
O
O-
+

27.  Glycosphingolipids are ceramides with one or
more sugar residues joined in a β-
glycosidic linkage at the 1-hydroxyl position
 Cerebrosides have a
single glucose or galactose at the 1-hydroxy
position.
 Sulfatides are sulfated cerebrosides.
 Gangliosides have at least three sugars, one
of which must be sialic acid.