Download MBBS Biochemistry PPT 2 L3 Lipid Alcohols Lecture Notes

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Alcohols Involved In

Lipid Structures
3 Alcohols Involved In

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Various Forms Of Lipids

1. Glycerol

(C3-Trihydric Alcohol)

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2. Sphingol/Sphingosine

(C18-Dihydric Alcohol)

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3. Cholesterol

(C27-Monohydric Alcohol)

Alcohols Of Lipids

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Are

Classified

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As

Derived Lipids

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Glycerol is a

Derived Lipid

Obtained from Hydrolysis of

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Simple and Compound Lipids
Glycerol/ Glycerin

? Glycerol [C3 ]is a POLYOL

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? Glycerol is chemically Trihydric

Alcohol (3 ?OH groups)

? Glycerol has potency to interact

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with 3 same or different Fatty

acids .

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vGlycerol is a backbone of

Glycerol based Lipids viz:

v Triacylglycerol

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v Glycerophospholipids
Glycerol Sources To Human Body

Endogenous and Exogenous Sources

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Glycerol

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Glucose

Source Of Glycerol To Human

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body

? Glucose is responsible for biosynthesis of Glycerol

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in human body

? Glucose transforms to Glyceraldehyde,

? Glyceraldehyde on reduction forms Glycerol.

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? Glycerol formed is then used for Biosynthesis

of Glycerol based Lipids.

? Glycerol released from hydrolysis of Glycerol

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based Lipids is transformed to Glucose.

SPHINGOSINE/SPHINGOL

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? Sphingosine is a derived

Lipid.

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? Obtained from Hydrolysis of

Sphingolipids
? Sphingosine is a C18, complex Dihydric,

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Amino alcohol.

? Sphingosine is biosynthesized in human

body using amino acid Serine.

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? Serine provides NH2 group of

Sphingosine.

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? Sphingosine forms Sphingolipids

/Compound Lipids with Alcohol

Sphingol

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? Examples of Sphingolipids:

?Sphingophospholipids
?Sphingoglycolipids

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What Is a Ceramide?

? A Fatty acid linked to an amino

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group of Sphingosine

? With an amide linkage form a

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Ceramide.


? Ceramide if linked to Phosphate and

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Nitrogenous groups forms

Sphingophospholipids.

? Ceramide linked to Carbohydrate

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moieties form Sphingoglycolipids.

Sphingosine Based Lipids
Sterols

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Common Sterol And Steroids

Vitamin D3

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Cholesterol

(cholecalciferol)

(a sterol)

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Testosterone

Stigmasterol

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(a steroid

(a phytosterol)

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hormone)
? Sterols are chemical y

complex, organic monohydric

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Alcohols.

? Sterols has cyclic ring

structures

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?Sterols have a parent ring
?Cyclo Pentano Perhydro

Phenantherene (CPPP)

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nucleus.
Examples Of Sterols

? Cholesterol (Animal Sterol)

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? 7 Dehydrocholesterol( Provitamin D)
? Coprosterol (Excretory form Cholesterol)
? Ergosterol (Plant Sterol)
? Sitosterol (Plant Sterol)

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Cholesterol

Most abundant Sterol of Human body
Cholesterol

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? Cholesterol is an Animal Sterol .

? Cholesterol means Solid Alcohol as it

was first obtained from gal stones of

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bile.

? Cholesterol is excreted via bile hence

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richly composed in bile ,Gal stones.

Cholesterol

Is A Derived Lipid

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? Cholesterol is classified as

Derived Lipid.

? It is derived from hydrolysis of

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Cholesterol Ester (Human Body

Wax).

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Chemical Structures Of

Cholesterol and Cholesterol Ester

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Pentahydrophenantrene

(Sterane)
Structure Of Cholesterol

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? Cholesterol is complex, cyclic,

unsaturated, monohydric Alcohol.

? Molecular formula is C27H45OH

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? Cholesterol has parent nucleus as

Cyclo Pentano Per hydro

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Phenantherene ring system(CPPP).

? The structure of CPPP has four

fused cyclic rings (A,B,C and D)

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? Hexane ring A,B,C is a

Phenatrene nucleus.

? D ring is Cyclopentane ring.

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? The Structure of Cholesterol Possess:

1. Hydroxyl group (-OH) at C3.

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2. Double bond between C5 and C6.

3. 5 Methyl (-CH3) groups.

4. 8 Carbon side chain linked to C17 of

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the structure.


Forms Of Cholesterol In Human Body

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? Cholesterol exists in two forms:

?Free Cholesterol - 30%

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(Amphipathic form)

?Cholesterol Ester - 70%

(Non polar form)

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Properties Of Cholesterol

? Cholesterol is white or pale yel owish,

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crystal ine ,odorless compound.

? Insoluble in water and soluble in organic

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solvents like Ether and Chloroform.

Crystals of Cholesterol Rhombic plates

with Notched edges.

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? Qualitative Tests For Cholesterol

detection are:

?Liebermann Burchard Reaction

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?Salkowski Reaction
?Zak's Reaction

Sources Of Cholesterol

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To Human Body
? Exogenous Sources of Cholesterol:

?Animal Origin Food Items

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? Endogenous Source Of Cholesterol:

?Obtained In wel fed condition from

Excess Glucose

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Dietary Sources Of Cholesterol

?Cholesterol is exclusively

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present in animal foods.


? The dietary rich sources of Cholesterol

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animal origin foods like:

?Egg Yolk
?Meat
?Milk

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?Butter
?Ghee
?Cream

?Remember Cholesterol

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is absent in plant origin

food items.
Endogenous Source Of Cholesterol

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? Cholesterol Biosynthesized in

human body from Free Excess

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Glucose in Liver.

Transportation Of Cholesterol

?Cholesterol in blood is

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transported by Lipoproteins:

? Chylomicrons ( Dietary origin)
? LDL (From Hepatocytes to Extra hepatocytes)

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? HDL (From Extra hepatocytes to Hepatocytes)
Occurrence and Distribution Of

Cholesterol in the Body

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?70 % of Cholesterol associated

with cel ular components

?30 % of Cholesterol is in the

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Blood.
? Cholesterol is richly present in Nervous

tissue Brain.

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? Other organs containing Cholesterol are:

?Liver
?Adrenal Cortex

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?Gonads
?Intestinal Mucosal cel s
?Skin

Functions Of Cholesterol

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Depends Upon

Quality and Quantity

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? Cholesterol is constituent of biomembranes

of cel

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? It give structure, shape and fluidity to them.

Effects on Membrane without Cholesterol

In Cold Environment In Hot Environment

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Rigid/ Not Flexible

Too Flexible

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Not Fluid

Very Fluid

May Get damage

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Not hold Shape
? Cholesterol richly present in

nervous tissue and covers

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Myelin sheaths.

? Cholesterol help in nerve

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impulse conduction.

? Cholesterol helps in nerve

impulse transmission since:

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?It has high dielectric constant.

?It is a poor conductor of heat

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and electricity.
Cholesterol Serves Precursor for

Biosynthesis Of Many Steroids

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Derivatives of Cholesterol

? Steroids are derivatives of Sterols.

? Chemical Compounds obtained

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from Cholesterol are termed as

Steroidal compounds.

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? Derivatives of Cholesterol

? Vitamin D (Cholecalciferol)
? Bile acids (Cholic and Chenodeoxycholic acid)

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? Bile Salts are obtained from Bile acids.
? Steroidal Hormones

? ACTH
? Mineralocorticoids

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? Glucocorticoids
? Sex Hormones: Androgens, Progesterone,

Estrogen and Testosterone

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Bile Acids and Bile Salts


Steroids Hormones

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Disorders Related To Cholesterol
?Serum Total

Cholesterol level of a

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Healthy human body is

150-200 mg%

Hypercholesterolemia

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? Causes for Hypercholesterolemia

? High intake of dietary Cholesterol(animal origin) is a

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exogenous source of Cholesterol.

? Elevated endogenous Cholesterol biosynthesis

when a very rich Carbohydrates is ingested.

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? Defect in Cholesterol transport by Lipoproteins in

blood retains Cholesterol in blood.

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Conditions Of Hypercholesterolemia

?Diabetes mellitus
?Obstructive Jaundice

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?Nephrotic Syndrome
?Hypothyroidism

? Hypercholesterolemia leads to :

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? Deposits of excess of

Cholesterol in blood vessels.

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? Atherosclerosis and atheroma

/plaque formation.

? Increased risk of ischemia and

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Myocardial infarction and

Stroke.
?Cholesterol Summary

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?Cholesterol is exclusively found only in

animals.

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?Exogeneous Cholesterol comes from diet
?Endogeneous Cholesterol is biosynthesized

by the Liver from Glucose product Acetyl-

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CoA.

?Cholesterol is an important component of

biomembranes, steroidal hormones, bile

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acids and Vitamin D