L I P I D S IIL I P I D S II

Simple Lipids

Neutral fats and oils Monoacyl glycerols (monoglycerides) Diacyl glycerols (diglycerides) Triacyl glycerols (triglycerides)

Triglycerides found in seeds and animal adipose tissue

Triacyl glycerols (triglycerides) Lipid storage form

Where in the body? Adipocytes!! Most lipids consumed are triglycerides

I- Triglycerides Most common structure in dietary lipids Composed of one glycerol molecule and three fatty acids connected

by an ester bond (bond between an alcohol and and organic acid) Fatty acids may be same or mixed

Glycerol

Fatty Acid

Fatty Acid

Fatty Acid

Triacyl glycerol (triglyceride)

II- WaxesII- WaxesWaxes are also esters like fats Use one alcohol instead of glycerolEsters of:

– Long-chain fatty acid– Long-chain alcohol

The longer the chains, the higher the melting pointProtects the skin of plants and fur of animals Examples of waxes include:

– Carnuba, from Brasilian wax palm – Beeswax

Complex Lipids -Phospholipids

Two primary types: Glycerophosphatides

Backbone structure is glycerol Part of cell membranes, chylomicrons,

lipoproteins Sphingophosphatides

Backbone structure is sphingosine Part of sphingomyelin

GlycerophospholipidsGlycerophospholipids (phosphoglycerides), are common constituents of cellular membranes.

They have a glycerol backbone.

Hydroxyls at C1 & C2 are esterified to fatty acids.

The C3 hydroxyl is esterified to Pi

O P O

O

O

H2C

CH

H2C

OCR1

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, glycerol, or inositol.

The 2 fatty acids tend to be non-identical. They may differ in length and/or the presence/absence of double bonds.

Glycerophospholipids

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

Phosphatidylinositol:

Phosphatidylcholine (Lecithin):

With choline as polar head group.

It is a common membrane lipid.

O P O

O

O

H 2 C

C H

H 2 C

OCR 1

O O C

O

R 2

C H 2 C H 2 N C H 3

C H 3

C H 3

+

p h o sp h a tid ylc h o lin e

O P O

O

O

H2C

CH

H2C

OCR1

O O C

O

R2

X

glycerophospholipid

Each glycerophospholipidincludes a polar region:

glycerol, carbonyl O of fatty acids, Pi, & the polar head group (X)

non-polar hydrocarbon tails of fatty acids (R1, R2).

Phospholipids …

Significant use in feed industry as emulsifiers Lipids form emulsion in water

Phospholipid sources: Liver, egg yolk, Soybeans, wheat germ Peanuts

H2CHC

OH

CH

N+ CH

C

CH2

CH3

H

H3

OH

( )12

sphingosine

are derivatives of the lipid sphingosine, which has a long hydrocarbon tail, and a polar domain that includes an amino group.

The amino group of sphingosine can form an amide bond with a fatty acid carboxyl, to yield a ceramide.

In the more complex sphingolipids, a polar “head group" is esterified to the terminal hydroxyl of the sphingosine moiety of the ceramide.

Sphingolipids:

H2CHC

OH

CH

NH CH

C

CH2

CH3

H

OH

( )12

C

R

O

ceramide

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

H2CHC

O

CH

NH CH

C

CH2

CH3

H

OH

( )12

C

R

O

PO O

O

H2C

H2CN+

CH3

H3C

CH3

Sphingomyelin

phosphocholine

sphingosine

fatty acid

Complex Lipids - Glycolipids

Carbohydrate component in structure Cerebrosides & gangliosides

Medullary sheaths of nerves; white matter of brain

Cerebrosides and gangliosides, collectively called glycosphingolipids, are commonly found in the outer leaflet of the plasma membrane bilayer.

cerebroside with -galactose head group

H2CHC CH

NH CH

C

CH2

CH3

OH

C

R

O

OH O

H H

H

OHH

OH

CH2OH

HO

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.

Disease Symptom Sph. Lip Enzyme

Tay-Sachs Blindness,

muscles weak

Ganglioside

GM2

-hexose-

aminidase A

Gaucher’s Liver & spleen enlarge, MR

Gluco-cerebroside

-glucosidase

Krabbe’s demyelation,

MR

Galacto-

cerebroside

-galactosidase

Nieman-Pick

MR Sphingomyelin

Sphingomyelinase

Sphingolipid Storage Diseases

C

H2C O

O

H2C O P

O

OH

O

C

O

R1

C

O

R2

CH2 C

OH

H

CH2 O P O

OH

O

CH2

C OH

CH2O

C

O

R3

C

O

R4

H

glycerolglycerol

glycerol

A polyglycerol phospholipid; makes up 15% of total lipid-phosphorus content of the myocardium – associated with the cell membrane

Cardiolipids are antigenic and as such are used in serologic test for syphilis (Wasserman test).

CH

HC

H2C

CH=CH(CH 2)12CH3

N H

HO

Storage (neutral) Membrane (polar)

G SFA

P

H2C

HC

H2C

(CH2)14CH3

(CH2)7CH=CH(CH 2)7CH3

(CH2)16CH3

OC

OC

OC

O

O

O

FA

FA

P A C MS/OS

FA

TAG

PL GL

GPL SL SL

TAG: triacylglycerol PL: phospholipids GPL: glycerophospholipidG: glycerolFA: fatty acid P: phosphate A: alcohol SL: sphingolipidC: choline GL: glycolipid S: sphingosineMS/OS: monosaccharide/oligosaccharide

ABDULLATIF TAHA ABDULLAABDULLATIF TAHA ABDULLADep. Of BIOCHEMISTRYDep. Of BIOCHEMISTRY