Phospholipids cholesterol
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Transcript of 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
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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)
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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
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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
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Phospholipids• the major components of cell membranes
– phosphoglycerides
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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
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Phosphatidyl inositol
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Commonly utilized in cellular signaling
Sphingolipids
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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)
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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
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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
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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
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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
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STEROIDS• Naturally occurring compounds having
perhydrocyclopentanophenanthrene nucleus in their structure
• The ring contains 17 carbon atoms • Generally contain CH3 at carbon 10 and 13
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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
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Animal sterol-cholesterol
• Chemical structure
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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
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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
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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
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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