Download MBBS Biochemistry PPT 3 L4 Simple Lipids Lecture Notes

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Study Of

Simple Lipids/Neutral Lipids

Triacylglycerols/Triglycerides
? Chemical name of Fat/Oil is Triacylglycerol
(TAG).

? TAG is a Simple, Glycerol based

,Neutral Lipid.

Chemical Structures Of

Triacylglycerol (TAG)


Triacylglycerol/Fats/Oils

? TAG/Fats/Oils are

? Chemically Esters of

? Three Fatty acids ( Same or Different)

? with one Glycerol (Trihydric Alcohol).
Most Common Fatty Acids in Triacylglycerol

Fatty acid

Carbon:Double bonds

Double bonds

Myristic

14:0

Palmitic

16:0

Palmitoleic

16:1

Cis-9

Stearic

18:0

Oleic

18:1

Cis-9

Linoleic

18:2

Cis-9,12

Linolenic

18:3

Cis-9,12,15

Arachidonic

20:4

Cis-5,8,11,14

Eicosapentaenoic

20:5

Cis-5,8,11,14,17

Docosahexaenoic

22:6

Cis-4,7,10,13,16,19

CH3(CH2)n COOH

?TAG is Neutral or Non

polar lipid.

?Since TAG structure has

no charged/polar groups

in its structure.


Types Of Triacylglycerol

Based On Nature Of Fatty Acid

?Simple TAG

?Mixed TAG
? Simple TAG: Three same Fatty

acids are esterified to Glycerol to

form simple TAG.

? Examples of Simple TAG:

?TriPalmitin
?TriStearin
?TriOlein

? Mixed TAG:

? The 3 different Fatty acids

esterified to Glycerol to form a

mixed TAG.

? Mixed TAG's are more

predominant in nature.


? In a Mixed TAG

? First Carbon C1 -has Saturated Fatty acid
? Second position C2-has Unsaturated

Fatty acid-PUFA

? The 3 rd position C3 Fatty acid in TAG has

- either Saturated/Unsaturated fatty

acid

Olive Oil Rich In Simple TAG

? Olive oil contains mostly TAG as Triolein, which has

three Oleic acids.
Sources OF Triacylglycerol

To

Human Body

?Exogenesis source of TAG :

?Dietary Fats/Oils

?Endogenous source of TAG :

?Liver Lipogenesis in wel fed

condition

?Using Glucose product Acetyl-

CoA.
Dietary Sources Of TAG

?Animal Fat (Solid)
?Plant Oils (Liquid)

Fats (solid Triacylglycerol)

Oil (a liquid Triacylglycerol)
Occurrence/Distribution Of TAG

qTAG is a most widely

distributed abundant

natural lipid.


TAG Major Lipid Form Of Human Body

?Predominant Lipid ingested

in Human diet is TAG 98%.

?Abundant Lipid of human

body Lipid is TAG 95 %.

Transportation Of TAG in

blood is By Lipoproteins

?Chylomicrons :

?Transports

exogenous dietary

TAG

?VLDL:

? Transports

endogenous TAG


Biomedical Importance Of TAG

S.No Distribution/Location Of TAG in Role of TAG

Human Body

1

Predominant Dietary Form of

Dietary and Calorific

Lipid Ingested in GIT

Value- Secondary

Source of Energy

2

Adiposecytes/Depot Fat-

Reservoir of Energy

Exclusively TAG

3

Subcutaneous layer /Below Skin Insuating Effect,

Regulates Body

Temperature

4

Fat Pad around Internal Soft

Mechanical Shock

Visceral Organs

absorbers
1.TAG Serves As Source Of Energy

? TAG has high calorific value

(9Kcal/gram) more than

Carbohydrates (4 Kcal/gram ).
2.TAG Reservoir Of Energy

Storage form of Lipid in

human body is TAG.
Triacylglycerols In Its Structure

Links and Stores Fatty acids

? Fatty acids are not stored in free

form in living beings.

? Fatty acids are stored in bound

form as TAG.

? Thus TAG is a storage form of

Fatty acids .


Criteria's For TAG To Be Chosen As

Reservoir of Energy

? TAG is highly reduced and

anhydrous form.

? Hence chosen as energy

reserve of the body.

? Because of insolubility of TAG in

aqueous phase:

? Body TAG are mostly found in

isolated compartments as

droplets.

? TAG in anhydrous form is packed

in Adipocytes

(Depot Fat)
3.Store House Of TAG

is High

In Comparison To

Glycogen Stores

? More content of energy can be

stored by TAG in comparison to

Glycogen stores.
? 1 gm of anhydrous TAG

stores more than 6 times as

much as energy as 1 gm of

hydrated Glycogen.

? Hydrated molecules requires more space.

? TAG stored in anhydrous form

requires less space.

? In contrast Glycogen being hydrated

requires more space.

(1 gm of Glycogen binds with 2gm of water)


? TAG When excess serves as

an energy reservoir stored in

Adipocytes as :

?Anhydrous form
?Concentrated
?Unlimited amount

?Stores of TAG are utilized in

between meals and

starvation phase.

?A good storage of depot

Fat can suffice for 2-3

months in starvation

condition.
? The stored TAG is used as long term

energy source for body activities.

? In long marathon race energy for

muscle activity is provided by the

hydrolysis of depot TAG.

4. TAG Regulates Body Temperature
? The subcutaneous Fat layer is a TAG
? TAG is a bad conductor of heat and

electricity and serves as a thermal

and electrical insulator.

? Which prevents loss of heat from the

body and plays important role in

regulating body temperature.

5.TAG Protects Internal Visceral

Organ and Systems


? A presence of Fatty (TAG) pad

around the soft delicate

internal visceral organs

? Protects from mechanical

trauma or injury by acting as

a shock absorber.

?TAG provides shape to

body and

?Keep skin smooth and

supple.
Remember TAG is

not associated to

biomembranes.

? MAG and DAG are derived

Lipids.

? Monoacylglycerol and

Diacylglycerol are hydrolytic

products of Triacylglycerol.

? These are produced during TAG

metabolism in the body.


?Monoacylglycerol (MAG)

/(Monoglycerides): A Glycerol esterified

with one fatty acid.

?Diacylglycerol (DAG) (Diglycerides):

?A Glycerol esterified with two fatty acids.

Healthy TAG In Human Body

? Ingesting Natural Mixed Form ? PUFAs and Short chain

FAs

? Avoiding Trans Fats

? Balanced/Moderate ingestion

? No excess or deficient TAG stores

? Normal serum TAG levels < 150 mg%


Disorders Associated To TAG

Bad About : TAG/ Fats and Oils

?Excess Fat leads to Obesity
?Increases risk for Diabetes Mel itus
?Leads to Coronary Artery disease
?MI, Stroke
? Susceptible to Cancer

50
Disorders Related To TAG

? Normal Fat content of adult:

?Men 21%
?Women 26%

? If the Fat content of an adult

body goes above the normal

content the condition is termed

as Obesity.






? Obesity has excess fat

depots.

? Truncal/central obesity is a

risk factor for heart attack.

? Obesity has abnormal Lipid

metabolism.

? Increased Blood Cholesterol and

Lipoproteins.


vObese persons has high risk of
vDiabetes mel itus
vAtherosclerosis and CVD
? Consequently lead to

Metabolic Syndrome




Prevent Obesity
Properties Of Triacylglycerol

Lipid Peroxidation

(autoxidation)
Lipid Peroxidation

Is a source of Higher Free Radicals

? During Oxygen metabolism in body.

? Oxygen derived free radicals (RO.,OH.,ROO.)

with unpaired electrons are released.

? These Reactive Oxygen Species (ROS) , Free

radicals interact and oxidize double bonds of

PUFAs leads to chain reactions of lipid

peroxidation.

? Steps of Lipid peroxidation

reaction:

?Initiation
?Propagation
?Termination
? PUFAs are more prone for

peroxidation.

? Lipid peroxidation Provide

continuous Free radicals.

? Thus has potential y

devastating effects in the

body.

? In vitro peroxidation of Lipids

deteriorates the quality of

Fats and Oils

? Makes the Fat/Oil rancid and in edible.

? Fat/oil has bad taste and odor

? Decreases the shelf life of Fats and Oils.
? In vivo peroxidation of

membrane Lipids damages cel s & tissues

? Lipid peroxidation has devastating

effects on body Lipids.

? Increases risk of Inflammatory diseases
? Ageing
? Cancer

? Antioxidants control and reduces
In vivo and In vitro Lipid peroxidation.

? Natural y occurring antioxidants are :

?Vitamin E
?Vitamin C
?Beta Carotene
? Body Enzymes as Antioxidants:

?Catalase
?Glutathione Peroxidase
?Superoxide Dismutase

? Other Substances as Antioxidants:

?Urate
?Bilirubin

? Food Additives as Antioxidants:

?Alpha Naphtol
?Gallic Acid
?Butylated Hydroxy Anisole (BHA)
?Butylated Hydroxy Toluene (BHT)
? Preventive Antioxidants:

? Reduces rate of Chain initiation of

Lipid peroxidation

?Catalase
?Peroxidase
?EDTA
?DTPA

? Chain Breaking Antioxidants:

? Interferes the chain propagation

of Lipid peroxidation.

?Vitamin E
?Urate
Rancidity Of Fats/Oils

Rancidity

? Rancidity is a physico chemical

phenomenon

? Which deteriorates Fats and Oils
? Resulting in an unpleasant taste

,odor and color of Fat/Oil

(Rancid Fat/oil)
?Rancid Fat is inedible

Factors Causing Rancidity
? Double bond containing /Unsaturated

Fatty acids are unstable and ready for

peroxidation and rancidity.

? Single bond containing/Saturated Fatty

acids are stable and less peroxidized

and made rancid.

PUFAs are more prone to

Rancidity

Since Double bonds are

more susceptible to Lipid

peroxidation
Causes Of Rancidity

? Fats and Oils get Rancid on Ageing.
? Various Factors aggravates rancidity of Oils

and Fats:

? Improper handling by an exposure to:

?Light
?Air (Oxygen)
?Moisture
?Microbes

Types and Mechanism

Of Rancidity
Types Of Rancidity

?Oxidative Rancidity
?Hydrolytic Rancidity
?Ketonic Rancidity

? Oxidative Rancidity:

? PUFAs having double bonds are

easily oxidized to form its

peroxides.

? By the action of Oxygen Derived

Free radicals (ODFR).
? The cel ular Lipids are also

likely to get peroxidized by

Free radical action causing

damage to biomembranes.

? Hydrolytic Rancidity:

? Long Chain Saturated fatty acids are

hydrolyzed by Bacterial Enzymes .

? To produce Dicarboxylic acids,

Aldehydes, Ketones etc which make

a Fat rancid.


















Ketonic Rancidity

? It is due to the contamination with

certain Fungi such as Asperigil us Niger

on Oils such as Coconut oil.

? Ketones, Fatty aldehydes, short chain

fatty acids and fatty alcohols are formed.

? Moisture accelerates Ketonic rancidity.

? Rancidity gives bad odor and

taste to rancid Fats/oils.

? Due to Dicarboxylic acids

,Ketones , Aldehydes Produced

during the process of




























Prevention of Rancidity of Fat/Oil By :



q Good storage conditions

q Less Exposure to light

q Low Oxygen, moisture

q No very High temperatures

q No Bacteria or fungalcontamination

q Addition of Antioxidants

Prevention Of Rancidity

? Rancidity can be prevented by

proper handling of oils

?By keeping fats or oils in wel

closed containers in cold,

dark and dry place.










Prevention Of Rancidity

?Avoid exposure to direct sunlight,

moisture and air.

?Avoid over and repeated heating of

oils and fats.



? Removal of catalysts such as Lead

and Copper from Fat/Oils that

catalyzes rancidity prevents

rancidity.






Antioxidants Prevent Rancidity

?Antioxidants are chemical

agents which prevent

peroxidation and

Hydrolysis of Fats/Oils.

? Examples Of Antioxidants:

? Tocopherol(Vitamin E)

? Vitamin C

? Propyl Gallate

? Alpha Napthol

? Phenols

? Tannins

? Hydroquinone's.

? Butylated Hydroxy Anisole(BHA)

? Butylated Hydroxy Toluene (BHT)




? The most common natural

antioxidant is vitamin E

that is important in vitro

and in vivo.

? Vegetable oils are associated with

high content of natural antioxidants

(Vitamin E),

? Hence oils do not undergo rancid

rapidly

? As compared to animal fats which

are poor in natural y associated

antioxidants .














? Rancidity of Fats and Oils is

prevented by adding Antioxidants.

? Thus addition of Antioxidants

increases shelf life of

commercial y synthesized Fats

and Oils.

Hazards of Rancid Fats:

1. Rancidity destroys the content of

polyunsaturated essential fatty acids.

2. Rancidity causes economical loss because

rancid fat is inedible.

3. The products of rancidity are toxic, i.e.,

causes food poisoning and cancer.

4. Rancidity destroys the fat-soluble vitamins

(vitamins A, D, K and E associated with it.
Others Properties Of TAG

Depends On Nature Of Fatty Acids

Chain Length Of Fatty acids

Of TAG affects Melting Point
? "Hardness" of the Fat/TAG depends on chain

length.

? < 10 carbons in Fatty Acid = liquid

? >20 carbons in Fatty Acid = solid

Acetic Acid (2 C)

Vinegar

Liquid

Stearic Acid (18 C)

Beef Tallow

Solid

Arachidic Acid (20 C) Butter

Solid

Differences In Fat and Oil

? Fat and Oils are different in Physical

Characteristics

? Fat is solid at room temperature.
? Oil is liquid at room temperature.


? TAG of Fat is solid since chemically

composed of long and saturated

fatty acids.

? Source of Fat is Animal foods.

? TAG of Oil is liquid as composed of

short and unsaturated fatty acids.

? Source of Oil is plant.
Hydrogenation Of Fat/Oil

? Treatment of Oils(TAG) rich in PUFAs with

Hydrogen gas, (H2).

? Catalyst required (Nickel).
? Adding Hydrogen at double bonds of PUFAs.
? It is also cal ed "Hardening of Oils"
? Hydrogenation converts PUFAs with cis form

to trans form.

? Margarine

? Vanaspati Dalda Crisco, Spry, etc.

Advantages and Disadvantages Of

Hydrogenation Of Fat /Fatty acids
Advantages Of Fat Hydrogenation

? Hydrogenation transforms unstable

,unsaturated , liquid TAGs:

?To stable, saturated, solid TAGs

?Reduces risk of Rancidity

?Increases shelf life and business.

?Example : Vanaspati Dalda ,Margarine.
Disadvantages Of Hydrogenation Of

Fat/Fatty acids

Trans Fats increases the risk of

Atherosclerosis and CVD.
? Hydrogenated trans Fats are

more stable.

? Body has no enzyme system to

oxidize and metabolize trans

fatty acids.

?Remember

Hydrogenated Fats

are Bad for Health.
? Summary Of Fat Hydrogenation:

? Hydrogen atoms are added to unsaturated

Fatty acids

?Make liquid oils more solid and more

saturated.

?Create trans fatty acids.

?Reduces peroxidation of Fatty acids.

?Resists rancidity

?Reduces metabolism

?Increases retention

?Increase risk of cardiovascular disease.

?Note

?Try eat more natural TAGs.
?Avoid Processed Fats.
Tests To Check Purity

Of

Fat and Oil

? Several laboratory tests are

employed to:

?Check the purity
?Degree of adulteration
?Biological value of Fat and

Oils.
Tests to Check Purity of Oils and Fats

Tests To Check Purity of Oils Importance/Significance

Iodine Number

Index of unsaturation and

content of unsaturated fatty

acids

Saponification Number

To know Chain Lengths of

Fatty acids

Acid Number

Checks purity of Refined oils

Reichert Meissl (RM)

Useful in testing the purity of

Number

butter
Iodine Number

? Iodine number is

Grams/Number of Iodine

absorbed by 100 gram of Fat

/Oil .

? Iodine Number is calculated by

method of Iodometry.

Use Of Iodine Number

? Iodine number is useful to

know

? The index of unsaturation and

content of unsaturated fatty

acids present in the Fat/Oil.
? Iodine number is directly

proportional to unsaturated

bonds of PUFAs in a Fat/Oil.

? High value of Iodine number of

oil indicates more content of

Unsaturated Fatty acids in it.

Name Of Oils

Iodine Number

Coconut Oil

7-10 (Least)

Butter

25-28

Ground Nut Oil

85-100

Sunflower Oil

125-145

Soya bean Oil

135-150

Linseed Oil /Flax seed 175-200 (Highest)

Oil
? Determination of Iodine number helps

in knowing the degree of

adulteration of tested oil sample.

? If Linseed oil is adulterated with an oil

whose content is high in saturated

fatty acids will give lower Iodine

number than the reference values.

Saponification Number

? Saponification number is

mil igram/number of KOH molecules

required to hydrolyze and saponify one

gram of Fat/Oil.
? Saponification number gives the

idea of molecular size/chain

length of Fatty acids present in 1

gram of Fat.

? 1 gram of Fat/oil with long chain

fatty acids has lower

saponification number.

? 1 gram of oil containing short chain

fatty acids has high Saponification

number.

? 1 gram Oil with short chain fatty

acids has higher saponification

number.

? Since it has more COOH groups for

KOH reaction.
? 1 gram Fat/Oil with long chain

fatty acids has low

saponification number.

? Since in 1 gram of Fat has few -

COOH groups of fatty acids to

react with KOH.

Oils

Saponification Number

Coconut Oil

250-260

Butter

230-250

Jojoba Oil

69- 80

Olive Oil

135-142
Acid Number

? Acid number is mil igram of KOH

required for complete

neutralization of free fatty acids

present in one gram of Fat/Oil.

? Acid number checks the purity of

Refined oils.

? Refined oils are free from free fatty

acids and has zero Acid number.

? Increased Acid number of refined

oil suggests bacterial/chemical

contamination and unsafe for

human consumption.
Reichert Meissl (RM)Number

? RM number is 0.1 N KOH

required for complete

neutralization of soluble

volatile fatty acids distil ed

from 5 gram of Fat .

?R.M Number of Butter is

25-30.

?The R.M number of

other edible oils is less

than 1.
? R.M number is useful in testing

the purity of butter

? Since it contains good

concentration of free volatile

fatty acids viz: Butyric, Caproic

and Caprylic acid.

?Adulteration of butter

reduces its R.M

number.
Differentiation Between

Fats And Oils

Fats

Oils

Fats are TAGs composed of Long

Oils are TAGs composed of short

and Saturated Fatty acid.

and Unsaturated Fatty acids.

Fats solid at room temperature

Oils liquid at room temperature

Fat has high melting point

Oils have low melting point

Fats -animal In Origin

Oils -Plant in Origin

Example: Lard (pork Fat)

Example: Safflower Oil

Fats has low antioxidant content

Oils have high antioxidant content

and get easily Rancid

and do not get easily Rancid

Fats are more stable

Oils are less stable

Fats are less metabolizable in body. Oils are readily metabolizable in the

body.

High content of dietary Fats has

Oils have low risk for

high risk for Atherosclerosis.

Atherosclerosis.

This post was last modified on 05 April 2022