phospholipids cholesterol

Saponification number

• gives some clue about the average size of fatty acids in a given sample of fat

• defined as the number of milligrams of KOH needed to neutralize the fatty acids in 1 g of fat

• butter (large proportion of short chain FAs) sap. no. 220 – 230

• oleomargarine (long chain FAs) sap. No is 195 or less

SELF RELIANCE FOR BETTER TOMORROW

SELF RELIANCE FOR BETTER TOMORROW

Acetyl number• some fatty acids have hydroxyl groups

(CH2)21H3C CH

OH

COOH

cerebronic acid

(CH2)5H3C CH CH2

OH

CH CH (CH2)7 COOH

ricinoleic acid

The acetyl number gives the proportion of these hydroxyl-containing fatty acids in a given sample of fat or oil

fatty acid

OH

acetic anhydridefatty acid

O C

O

CH3

fatty acid

OH

+

COOHH3C

titrate with standardizedKOH

acetylated fatty acid

Acetyl number• the acetyl number is the number of

milligrams of KOH needed to neutralize the acetic acid produced from 1 g of acetylated fat– examples:

• castor oil (146 –150)• cod liver oil (1.1)• cottonseed oil (21 – 25)• olive oil (10.5)• peanut oil (3.5)

SELF RELIANCE FOR BETTER TOMORROW

Iodine number

• measures the degree of un-saturation in a given amount of fat or oil

• the iodine number is the number of grams of iodine absorbed by 100 g of fat

• Cottonseed oil: 103 –111• Olive oil: 79 – 88• Linseed oil: 175 –202

• frequently used to determine adulteration of commercial lots of oils

SELF RELIANCE FOR BETTER TOMORROW

HHI I

HHI2

Reichert–Meissl number

• measures the amount of volatile fatty acids (low MW and water soluble Fats)

• the R-M number is the number of milliliters of 0.1N alkali required to neutralize the soluble fatty acids distilled from 5 g of fat

• butter fat has a high R-M number

SELF RELIANCE FOR BETTER TOMORROW

Phospholipids• the major components of cell membranes

– phosphoglycerides

SELF RELIANCE FOR BETTER TOMORROW

O R

O R'

O

P

O

O

O

O-

X

Ofatty acids (hydrophobic tail)

glycerol

phosphate

Phospholipids are generally composed of FAs, a nitrogenous base, phosphoric acid and either glycerol, inositol or sphingosine

O R

O R'

O

P

O

O

O

O-

X

Ofatty acids (hydrophobic tail)

glycerol

phosphate

X = H (phosphatidic acid) - precursor to other phospholipids

X = CH2-CH2-N+(CH3)3 phosphatidyl choline

X = CH2-CH(COO-)NH3+ phosphatidyl serine

X = CH2-CH2-NH3+ phosphatidyl ethanolamine

SELF RELIANCE FOR BETTER TOMORROW

Phosphatidyl inositol

SELF RELIANCE FOR BETTER TOMORROW

Commonly utilized in cellular signaling

Sphingolipids

SELF RELIANCE FOR BETTER TOMORROW

OH

NH2

OH

NH2

OH

HO R long chain hydrocarbon

attach fatty acid here

attach polar head group here

sphingosine

Contain sphingosine instead of glycerol

1- phingomyelin (a ceramide)

SELF RELIANCE FOR BETTER TOMORROW

It is a omnipresent component of animal cell membranes, where it is the most abundant sphingolipid. It can comprise as much as 50% of the lipids in certain tissues.It is usually lower in concentration than phosphatidylcholine

2-Ether glycerophospholipids• Possess an ether linkage instead of an acyl

group at the C-1 position of glycerol– platelet activating factor (PAF)

– A potent mediator in inflammation, allergic response and shock, also responsible for asthma-like symptom

– The ether linkage is stable in either acid or base

– Plasmalogens: cis , -unsaturated ethers• The alpha/beta unsaturated ether can be

hydrolyzed more easily

SELF RELIANCE FOR BETTER TOMORROW

SELF RELIANCE FOR BETTER TOMORROW

3- Ether glycerophospholipids

H2C CH

O

CH2

O

O

P

O

-O O

C O

CH3

CH2 CH2 N

CH3

CH3

CH3

platelet activating factor or PAF

H2C CH

O

CH2

O

O

P

O

-O O

C O

CH2 CH2 N

CH3

CH3

CH3

A choline plasmalogen

H

H

4-Glycolipids

SELF RELIANCE FOR BETTER TOMORROW

NH

O

HO R

R'

O

SUGAR polar head is a sugar

beta linkage

There are different types of glycolipids: cerebrosides, gangliosides,lactosylceramides

GLYCOLIPIDS• Cerebrosides

• One sugar molecule– Galactocerebroside – Glucocerebrosides

• Sulfatides or sulfogalactocerebrosides• A sulfuric acid ester of galactocerebroside

• Globosides: ceramide oligosaccharides• Lactosylceramide

– 2 sugars ( eg. lactose)

• Gangliosides• Have a more complex oligosaccharide attached• Biological functions: cell-cell recognition; receptors for

hormonesSELF RELIANCE FOR BETTER TOMORROW

5- Cardiolipids

SELF RELIANCE FOR BETTER TOMORROW

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-phosphoruscontent of the myocardium – associated with the cell membrane

6-Sulfolipids

• also called sulfatides or cerebroside sulfates• contained in brain lipids• sulfate esters of cerebrosides• present in low levels in liver, lung, kidney,

spleen, skeletal muscle and heart• function is not established

SELF RELIANCE FOR BETTER TOMORROW

STEROIDS• Naturally occurring compounds having

perhydrocyclopentanophenanthrene nucleus in their structure

• The ring contains 17 carbon atoms • Generally contain CH3 at carbon 10 and 13

SELF RELIANCE FOR BETTER TOMORROW

A B

C D1

2

3

45

6

7

89

10

1112

13

14 15

16

1718

19

Animal sterol-cholesterol• It is the most abundant steroid• Found in animal tissues and not in plants• 140 g of cholesterol is present in normal

human adult• Structural formula is C27H45OH

• Considering asymmetric carbon atoms 512 stereoisomers are possible

• The most abundant isomers are C3 (OH) and C5-10 fusion

SELF RELIANCE FOR BETTER TOMORROW

Animal sterol-cholesterol

• Chemical structure

SELF RELIANCE FOR BETTER TOMORROW

Iso-octanyl at C17

Un-saturation between C5 and C6OH at C3

CH3 at 10 and 13

CHOLESTEROL FACTS

It is synthesized from acetyl CoA and eliminated as bile acids

It is a precursor of all other steroids in the body

It is a product of animal metabolism – found in foods of animal origin

It is an amphipathic lipid (hydrophobic and hydrophilic portions)

stored in the form ester in most of tissues.

HO

hydrophilic

O || R-C-O

Cholesterol ester (1st ring only)R = fatty acid hydrocarbon chain

SELF RELIANCE FOR BETTER TOMORROW

white crystalline solid, tasteless and odorless

oxidized on exposure to air

acts as insulator to nerves and brain tissue

essential structural component of membranes

transported in the circulation in lipoproteins

physical properties

SELF RELIANCE FOR BETTER TOMORROW

The physiological roles of cholesterol include:

a) an important lipid component of biological membranes b) precursor of steroid hormones and c) source of bile acids

ROLES OF CHOLESTEROL AND BILE ACIDS AND ITS SALTS

Bile acids are polar derivatives of cholesterol and aid in:

a) lipid digestionb) lipid absorptionc) cholesterol excretion

SELF RELIANCE FOR BETTER TOMORROW

SELF RELIANCE FOR BETTER TOMORROW

Cholesterol

Cholestanone (ketones)

Oxi

datio

n

Drastic oxidation

Mixture of ketones and hydroxy acids

Carboxylic acids

Cholesterol esters

Cholesterol dihalides Dihydrocholesterol

hal

oge

ns

hyd

roge

n