Lipid ChemistryPresented By

Ayman Elsamanoudy

Salwa Abo El-khair

4

1. By the end of this chapter the student should be able to:

define lipids.

describe the biological importance of lipids.

point out basic lipid chemistry.

classify lipids.

explain the chemistry and main function of simple, compound

and derived lipids.

2. By the end of this chapter the student should be able to

apply biochemical knowledge on analyzing biochemical bases of

the diseases through case study.

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Objectives:

Compound Lipids

Compound Lipids

Compound (conjugated) lipids are lipids

conjugated with other substances.

They include:

Phospholipids :

(lipid+ phosphoric acid + nitrogenous base).

Glycolipids :(lipid + carbohydrate).

Sulpholipids :(lipids + sulphate).

Lipoproteins :(lipid + protein).

Phospholipids They are a group of compound lipids formed of:

Alcohol &Fatty acids

+

Phosphoric acid

+

Nitrogenous base (may be).

They are classified according to the alcohol into:

Phosphoglycerides

Sphingomyelin

Phosphoglycerides

In which nitrogen phosphorous ratio (N/P

ratio =1) is 1

i.e. they contain one nitrogen and one

phosphate.

Sphingomyelin

in which N/P ratio is 2

i.e. it contains 2 nitrogen and one phosphate.

A- Phosphoglycerides

Phosphoglycerides are a group of phospholipids

containing glycerol with N/P ratio = 1.

They include:

Phosphatidic acid

Lecithin,

Cephalins,

Phosphatidyl inositol

Plasmalogen

Cardiolipin.

1- Phosphatidic acid

It is phosphoric acid ester of diglycerides.

Structure:

Glycerol.

Saturated fatty acid , attached to α carbon of

glycerol by ester bond.

Unsaturated fatty acid, attached to β carbon of

glycerol by ester bond.

Phosphoric acid attached to α carbon of glycerol

by ester bond.

Function of phosphatidic acid

It is an intermediate compound

in biosynthesis of other

phosphoglycerides and triglycerides

2- Lecithin

It is phosphatidyl

choline.

It is formed of:

Glycerol.

Saturated fatty acid,

Unsaturated fatty acid,

Phosphoric acid,

Choline attached to

phosphoric acid by ester

bond.

This means :phoshatidic

acid + choline base

Function of lecithin

1. It is the most abundant phospholipids in the

cell membrane.

2. It acts as a lipotropic factor

(substances that prevent accumulation of lipids

in the liver).

3. Dipalmityl lecithin acts as Lung surfactant

(substances that line the lung alveoli forming a

layer at the interface of fluid lining the

alveoli and air inside alveoli preventing lung

collapse).

Respiratory Distress Syndrome (RDS)

Incidence :In premature infants .

Causes : the lung alveoli don’t secrete sufficient

amount of lecithin.

Effect : lung collapse.

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Lysolecithin

Snake venom contains

lecithinase enzyme,

which removes the unsaturated fatty acid from

lecithin forming lysolecithin.

Lysolecithin is a strong surface- active

substance that has a marked haemolytic action

causing haemolysis of the red blood cells.

Lysolecithin

Cephalins

They are phosphatidyl ethanolamine & phosphatidyl serine

Structure

They are formed of:

Glycerol.

Saturated fatty acid

Unsaturated fatty acid,

Phosphoric acid.

Ethanolamine or serine.

CH

CH

CH

O

O

O

COR1

COR2

HPO4 CH2 CH2 NH2 CH2 CH2 NH2Ethanolamine

CH

CH

CH

O

O

O

COR1

COR2

HPO4 CH2 CH COOH

NH2

CH2 CH COOH

OH NH2Serine

phosphatidyl ethanolamine

phosphatidyl serine

Phosphoglycerides3- Cephalins

HO

HO

Phosphatidyl-serine

Phosphatidyl-ethanolamine 17

Function of cephalins

They have a role in blood coagulation.

They accelerate blood clotting because they

share in the structure of thromboplastin, which

is essential for blood clotting.

4- Phosphatidyl inositol (lipoinositol).

Structure

It is formed of: Glycerol.

Saturated fatty acid,

Unsaturated fatty acid,

Phosphoric acid

Inositol, which is a cyclic alcohol derived from glucose.

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CH2

C HO

CH2

C

O P

R2

O

-Phosphatidylinositol

O

OH

O

C R1

O

O

H

H

OH

OH

HOH

H

OHOH

H H

1

2 3

4

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Function of phosphatidyl inositol:

It is found in brain tissue.

It has a role in mechanism of hormone action.

on hydrolysis by phospholipase C enzyme, it gives

compounds that acts as second messengers in

hormone action e.g. diacyl glycerol (DAG) and

inositol triphosphate (IP3).

5- Plasmalogens:

Structure

It is formed of:

Glycerol.

(unsaturated alcohol) at

α position. (fatty aldehyde

in the enol form)

Unsaturated fatty acid at β position.

Phosphoric acid.

Nitrogenous base, which may be choline, ethanolamine or

serine.

SO, They are lecithin or cephalin in which the fatty acid

attached to α carbon is replaced by unsaturated alcohol .

Function of plasmalogens

They are present in cardiac muscle, skeletal

muscles and brain.

6- Cardiolipin

It is a diphosphatidyl glycerol formed of 2

phosphatidic acids attached together by

glycerol.

CH2

C HO

CH2

C

O P

R2

O

Cardiolipin

O

OH

O

C R1

O

O

CH2

CH OH

CH2

CH2

CH O

CH2

C

OP

R3

O

O

OH

O

CR4

O

O

Structure of Cardiolipin

It is formed of: 3 glycerol molecules.

2 saturated fatty acids.

2 unsaturated fatty acids.

2 molecules of phosphoric acid.

Functions of cardiolipin

Cardiolipin is present in heart muscle.

It is used as antigen for detection of syphilis.

B- Sphingomyelins

Sphingomyelin is a phospholipids with N/P ratio

= 2.

sphingomyelin contains sphingosine base (18 C).

It is called Sphingol ; long chain unsaturated

amino alcohol) instead of glycerol.

Sphingolipids

Ceramide

It is formed of sphingosine base to which fatty acid is

attached by amide linkage.

Structure of sphingomyelin

Sphingosine base.

Unsaturated fatty acid (to the amino group of

sphingosine by amide link).

Phosphoric acid (to the primary alcoholic group of

sphingosine by ester bond ).

Choline base attached to phosphoric acid by ester

bond .

Sphingomyelin

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Function sphingomelin

It is abundant in the nervous system in the myelin

sheath .

It is present to lesser extent in liver, spleen and bone

marrow.

N.B: Nimann Pick disease

It is a disease caused by deficiency of

sphingomelinase enzyme, which catabolizes

sphingomyelin.

This leads to accumulation of large amounts

of sphingomelin in liver, spleen and brain.

Sphingophospholipidsphosphoglycerides

Sphingosine base

(sphingol alcohol)Glycerol Alcohol

-One

-( usually long

unsaturated )

-linked by amide link

-2FA

-(at α position is saturated &

at β is unsaturated )

-linked by ester bond

Fatty acids

One One Phosphate group

Choline base Differ according to the type Nitrogenous Base

21N/P ratio

Negative Positive Acroline test

SphingomyelinePhosphatidic acid ,lecithen,

cephalines,plasmalogen and

cardiolipin

Types

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Lipid ChemistryPresented By

Ayman Elsamanoudy

Salwa Abo El-khair

5

Glycolipids

They are compound lipids

(carbohydrates +lipids).

They contain sphingosine base

They include cerebrosides and gangliosides.

1- Cerebrosides

They are called cerebrosides because they are

present mainly in the brain and nerves.

Cerebrosides Structure

Sphingosine base.

Long chain fatty

acid attached to

the amino group

of the sphingosine

base by amide linkage.

Carbohydrate usually

galactose but may be

glucose.

According to the fatty acid present,

Cerebrosides are classified into:

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OxynervonnervonCerebronkerasin

Hydroxy-

nervonic acid

Nervonic acid Cerebronic

acid

Lignoceric

acid

FA

24242424Number of

its C-

atoms

Monounsaturated Monounsaturated Saturated SaturatedDegree of

saturation

hydroxy FANon hydroxy

FA

hydroxy

FA

Non

hydroxy FA

Hydroxyl

group

Functions of cerebrosides

1. They are present mainly in the nervous

tissues i.e. brain and nerves.

- They act as electric insulators of nerve

impulses.

2. Also, they are present in spleen, liver,

adrenal gland, kidney and lungs.

2- Gangliosides

These are the most complex glycolipids.

Structure

Sphingosine base.

Long chain fatty acid.

One glucose molecule.

2 galactose molecules.

N-acetyl galactosamine.

N-acetyl neuraminic acid (siailic acid; NANA).

Function

Gangliosides are present in high concentration in brain.

They act as receptors at cell membrane.

Lipid part

CHO part

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Sulpholipids

They are cerebrosides containing sulphate group

attached to C3 of galactose.

Structure:

Sphingosine base.

Long chain fatty acid (attatched to the amino

group of the sphingosine base).

Carbohydrate usually galactose but may be

glucose.

Sulphate group (attatched to C3 of galactose).

Structure of supholipids

• Function

• They are

present in

brain and

nervous

tissues.

Structure of galactosylceramide (galactocerebroside, R

= H), and sulfogalactosylceramide (a sulfatide, R =

SO42- )

Lipoproteins

These are compound lipids formed of :

lipid part (triglycerides, cholesterol or

phospholipids) &

protein part (α or β globulin).

Function of lipoproteins:

In the structure of cell membrane.

Lipid transport in the blood (Lipids are insoluble in

water). Lipids bind to protein to make lipoproteins

water-soluble to be transported in the blood.

• Each contains different

kinds and amounts of

lipids and proteins

– The more protein,

the higher the

density

– The more lipid, the

lower the density

• Each has different

function

Lipoproteins

Hydrophobic lipids

Amphiphilic lipids

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Structure of lipoprotein

Hydrophobic lipids (TG, CE) in the core

Amphiphilic lipids (C, PL) and proteins on the surface

Separation of lipoproteins

Lipoproteins can be separated by:

1- Ultracentrifugation

In NaCl solution, lipoproteins are separated by

ultracentrifugation, as they differ in the degree of

floatation, into :

chylomicrons, VLDL, LDL and HDL.

2- Electrophoresis

As they differ in migration rate due to differences in

molecular weight and charge, lipoproteins are

separated into :

chylomicrons, pre β, β and α lipoproteins.

3- Chromatography

According to

ultracentrifugation

-Chylomicrons,

-Very low-density

lipoproteins

-Low-density

lipoproteins

-High-density

lipoproteins

According to

electrophoresis:

-Chylomicrons,

-Pre-β lipoproteins,

-β lipoproteins,

-α lipoproteins.

Lipoproteins

Anode

+

Cathode

---

α lipoproteins Pre-β lipoproteins β lipoproteins Chylomicrons

(HDL) (VLDL) (LDL)

LipoproteinsChylomicrons VLDL

Site of synthesis

Small intestine Liver

Structure Mainly triglycerides, small amount of cholesterol, phospholipids and protein

Mainly triglycerides, greater amount of cholesterol, phospholipids and protein

Lipoproteins

LDL HDL

Site of synthesis

Liver

Blood

Liver

Structure Mainly cholesteroland good amount of proteins, phospholipids and triglycerides

Mainly proteinsand phospholipids, small amount of cholesterol and little amount of triglycerides

Chylomicron VLDL LDL HDL

Size Largest Large Small Smallest

Rate of float-ation

Highest High Low Lowest

Electro-phoresis

Do not migratebecause of their highcontent of triglycerides (have high molecular weight and no charges).

Migrate after β globulin

Migrate with β globulin

Migrate with α globulin

Chylomicron VLDL

Function Transport exogenous triglycerides from the small intestine to tissues.

Transport endogenous triglycerides from the liver to tissues.

LDL HDL

Function Transport cholesterol from the liver to tissues.

Retrograde transport of cholesterol from the tissues to liver.

Transport phospholipids from the liver to tissues.

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HDLLDLVLDLChylomicron

Mainly in LiverBloodLiverSmall intestineSite of

synthesis

Very smallSmallLargeLargestSize

Mainly of

proteins and

phospholipids,

small amount of

cholesterol and

little amount of

triglycerides

Mainly

cholesterol and

appreciable

amount of

proteins,

phospholipids

and triglycerides

Principally

triglycerides,

greater amount of

cholesterol,

phospholipids

and protein

Mainly triglycerides,

small amount of

cholesterol,

phospholipids and

protein

Structure

Transport

from cholesterol

the tissues to the

liver (reverse

cholesterol

transport

Transport

from cholesterol

the liver to the

tissues.

Transport

endogenous

from triglycerides

the liver to the

tissues

exogenous Transport

from triglycerides

the small intestine to

the tissues.

Functions

Lowest Low High Highest Rate of

floatation

Migrate with α

globulin

Migrate with β

globulin

Migrate before β

globulin

Do not migrate Electrophore

sis

Activity 1- Give the hydrolytic products of the followings:

1-Lecithen

2- Cephalins

3- Cardiolipis

2-Compare between each of the followings :

1-Phosphoglycerides& sphingophospholipids

2-Chylomicron and HDL.

3- cerbrosides and gandliosides

3- enumerate the types of lipoproteins & mention the

main function of each of them 61

4-Enumerate:

1-lipids that contain choline base.

2- lipids that contain sphingol alcohol.

3-lipids that contain galactose sugar.

4- Methods of separation of lipoproteins

5- what is the type of bond in each of the following:

1- TAG

2-Ceramide.

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Choose the best correct nswer

Ceramide is a constituent of the following EXCEPT:

a) cerebroside

b) sulfatides

c) sphingomyelins

d) lecithen

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11/17/2014 64Ahmed A.Albadry

GREAT

THANKS

Ayman Elsamanoudy

Salwa Abo El-khair