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FATS

Dr. Daxaben N. Mehta
Principal
Smt. Sadguna C.U.Shah Home Science and
C. U. Shah Arts & Commerce Mahila College,
Wad...
Fats
• We all need some fat in our diet for
energy.
• Some fats are not good for us, like fried
foods.
• Only 10% of our d...
Chemistry of Lipids

Definition:
• - Lipids are organic compounds formed
mainly from alcohol and fatty acids
combined toge...
Chemistry of Lipids

• - Lipids are insoluble in water, but
soluble in fat or organic solvents (ether,
chloroform, benzene...
Biological Importance
of Lipids
:

1. Palatable and storable to unlimited amount
2. High-energy value (25% of body needs),...
Biological Importance
of Lipids
7-Stored lipids “depot fat” acts as: A store of energy.
• A pad for the internal organs to...
Classification of Lipids

1.
2.
3.
4.

Simple lipids (Fats & Waxes)
Compound or conjugated lipids
Derived Lipids
Lipid-ass...
Fatty alcohols
1-Glycerol:

• Trihydric alcohol (i.e., containing
three OH groups), popular name
glycerin.
• Synthesized i...
Properties
1. Colorless viscous oily liquid with sweet taste.
2. On heating with sulfuric acid or KHSO4
(dehydration) it g...
Properties
3 Combines with three molecules of nitric acid
trinitroglycerin (TNT) used as explosive and vasodilator.
4 On e...
Uses of Glycerol
1. Pharmaceutical and cosmetic preparations.
2. Reduces brain edema in cerebrovascular
disease.
3. Nitrog...
2-Sphingosine

• - It is the alcohol(monohydric) present in
sphingolipids.
• - It is synthesized in the body from serine a...
Fatty Acids
Definition:
• Fatty acids are aliphatic mono-carboxylic acids
mostly obtained from the hydrolysis of natural
f...
I. According to pre. or
abs.of double bonds
• A-Saturated Fatty Acids
• they contain no double bonds with 2-24 or
more car...
Saturated fatty acids
A-Short chain Saturated F.A. (2-10 carbon).
a-Short chain Saturated volatile F.A.(2-6
carbon).
b- Sh...
Volatile short-chain
fatty acids:
They are liquid in nature and contain (1-6)
carbon atoms.
• water-soluble and volatile a...
Non-volatile short-chain
fatty acids
• They are solids at room temperature
and contain 7-10 carbon atoms.
• They are water...
Long-chain fatty acids
• They contain more than 10 carbon atoms.
• They occur in hydrogenated oils, animal
fats, butter an...
Unsaturated Fatty Acids
They contain double bond
• monounsaturated
they contain one double bonds .
(CnH2n-1 COOH)
• polyun...
Monounsaturated
fatty acids
1-Palmitoleic acid :
• It is found in all fats.
• It is C16:1∆9, i.e., has 16 carbons and one
...
Monounsaturated
fatty acids
2-Oleic acid
• Is the most common fatty acid in natural
fats.
• It is C18:1∆9, i.e., has 18 ca...
Monounsaturated
fatty acids
3-Nervonic acid
(Unsaturated lignoceric acid).
• It is found in cerebrosides.
• It is C24:115...
Polyunsaturated
fatty acids
(Essential fatty acids):
• They are essential fatty acids that can not
be synthesized in the h...
Polyunsaturated
fatty acids
• Source: vegetable oils , corn, linseed
, peanut, olive, cottonseed, soybean and many
other p...
Function of Essential
Fatty Acids
1. Useful in the treatment of atherosclerosis by transport
of blood cholesterol, triglyc...
Essential F A
1-Linoleic: 18:29, 12.
• It is the most important since other
essential fatty acids can be synthesized
from...
Essential F A

2-Linolenic acid:
• C18:39, 12, 15,
• in corn, linseed, peanut, olive, cottonseed and
soybean oils.
CH3-CH...
Essential F A
3-Arachidonic acid:
• C20:45, 8, 11, 14.
• It is an important component of
phospholipids in animal and in p...
1-Simple Lipids
A-Neutral Fats and oils (Triglycerides)

Definition:
• Called neutral because they are uncharged due to
ab...
1-Simple Lipids
• Esterification of glycerol with one molecule
of fatty acid gives monoglyceride, with 2
molecules diglyce...
Types of triglycerides
1-Simple triglycerides: Three fatty acids connected to
glycerol are of same type the triglyceride i...
O
CH 2

O
CH 3

(C H 2 ) 14

C

O

C

O

C

(C H 2 ) 14

CH 3

H
O

CH 2

O

C

(C H 2 ) 14

CH 3

T r ip a lm itin
(s im ...
Fats & Oils

•

The commonest fatty acids in animal fats are
palmitic, stearic and oleic acids.
• The main difference betw...
Physical properties
of fat and oils:
1. Fats and oils are colorless, odorless and tasteless.
Any color, or taste is due to...
1-Hydrolysis:
Hydrolyzed into their constituents (fatty acids and
glycerol) by the action of super heated steam, acid, alk...
2-Saponification
Alkaline hydrolysis produces glycerol and salts of
fatty acids (soaps).
• Soaps cause emulsification of o...
3-Halogenation

• unsaturated fatty acids have the ability of adding halogens
(e.g., hydrogen or hydrogenation and iodine ...
4-Hydrogenation
or hardening of oils
• Addition reactions accepting hydrogen at the
double bonds of unsaturated fatty acid...
Advantages &
Disadvantages
1.
2.
3.
4.

•

Advantage
More pleasant as cooking fat.
Digestible and utilizable as normal ani...
5-Oxidation(Rancidty)
• Toxic reaction of triglycerides leads to
unpleasant odour or taste of oils and fats
developing aft...
Rancidity
• Physico-chemical change in the natural
properties of the fat leading to the
development of unpleasant odor or ...
Types and causes
of Rancidity:

1. Hydrolytic rancidity
2. Oxidative rancidity
3. Ketonic rancidity
1-Hydrolytic rancidity...
Hydrolytic rancidity
O

O
O

H 2 C OH

CH 2 O C R 1

R2 C O C H

Lipase

HO C H

O

CH 2 O C R 3

Triacylglycerol

Home Sc...
2-Oxidative Rancidity
Oxidation of fat or oil catalyzed by exposure to
oxygen, light and/or heat producing peroxide
deriva...
Oxidative Rancidity
P o ly u n s a tu ra te d fa tty a c id
O x id a n t, O 2
P e r o x y ra d ic a l
C y c lic p e r o x ...
3-Ketonic Rancidity
• It is due to the contamination with
certain fungi such as Asperigillus Niger
on fats such as coconut...
Prevention of rancidity
1. Avoidance of the causes (exposure to light, oxygen,
moisture, high temperature and bacteria or ...
Hazards of Rancid Fats
1. The products of rancidity are toxic, i.e.,
causes food poisoning and cancer.
2. Rancidity destro...
Analysis and Identification
of fats and oils
• Fat constants or numbers are tests used for:
1. Checking the purity of fat ...
1-Iodine number
• Definition: Number of grams of iodine absorbed by
100 grams of fat or oil.
• Uses: Measure for the degre...
2-Saponification number
• Definition: Number of milligrams of KOH required to
completely saponify one gram of fat.
• Uses:...
3-Acids Number
• Definition:
• Number of milligrams of KOH required to
neutralize the free fatty acids present in one
gram...
4-Reichert- Meissl
Number
• Definition: Number of milliliters of 0.1 N KOH
required to neutralize the water-soluble fatty ...
5-Acetyl Number
• Definition: Number of milligrams of KOH needed to
neutralize the acetic acid liberated from hydrolysis o...
2-Compound Lipids
Definition:
• Lipids that contain additional substances, e.g.,
sulfur, phosphorus, amino group, carbohyd...
A-Phospholipids
Definition: Phospholipids or phosphatides compound lipids,
Having phosphoric acid group in their structure...
A-Phospholipids
5-Important in digestion and absorption of neutral lipids
and excretion of cholesterol in the bile.
6-Impo...
Sources & Structure
They are found in all cells (plant and animal),
milk and egg-yolk in the form of lecithins.
1. Fatty a...
Classification of Phospholipids
• Classified into 2 groups acc. to type of alcohol present
A- Glycerophospholipids: They a...
A- Glycerophospholipids

1-Phosphatidic acids :Metabolic intermediates in synthesis of triglycerides
and glycerophospholip...
2-Lecithins
• Definition: Lecithins are glycerophospholipids contain
choline as a base beside phosphatidic acid, exist in ...
Lysolecithin causes hemolysis of RBCs. This partially
explains toxic the effect of snake venom,. The
venom contains lecith...
•

Lung surfactant

•

Is a complex of dipalmitoyl-lecithin, sphingomyelin and a
group of apoproteins called apoprotein A,...
3-Cephalins (or Kephalins):
• Definition: They are
phosphatidyl-ethanolamine
or serine. Cephalins occur in
association wit...
• Certain cephalins are constituents of the complex mixture of
phospholipids, cholesterol and fat that constitute the lipi...
4-Plasmalogens:
• Definition: Plasmalogens are found in the cell
membrane phospholipids fraction of brain and
muscle (10% ...
• Properties: Similar to lecithins.
CH 2

O
R2

C

O

C

O

CH

H

CH 3

O
CH 2 O P

O CH 2 CH 2 N

OH

 -P la s m a lo g...
5-Inositides:
• Definition:
• - They are phosphatidyl inositol.
• Structure: They are similar to lecithins or cephalins bu...
• Source: Brain tissues.
• Function:
• Phosphatidyl inositol is a major component of cell
membrane phospholipids particula...
6-Cardiolipins:

:

• Definition They are diphosphatidyl-glycerol. They are
found in the inner membrane of mitochondria in...
B-Sphingophospholipids
1-Sphingomyelins
• Definition: Sphingomyelins are found in large amounts in
brain and nerves and in...
• Ceramide This part of sphingomyelin in which the
amino group of sphingosine is attached to the fatty acid by
an amide li...
B-Glycolipids

:

•

Definition They are lipids that contain carbohydrate

•

residues with sphingosine as the alcohol and...
1-Cerebrosides:
• Occurrence: They occur in myelin sheath of nerves and white matter of the
brain tissues and cellular mem...
• Types: According to the type of fatty acid and

1.
2.
3.
4.

carbohydrate present, there are 4 different types
of cerebr...
2-Sulfatides:
• They are sulfate esters of kerasin or phrenosin in which the
sulfate group is usually attached to the –OH ...
3-Gangliosides:
• They are more complex glycolipids that occur in the gray
matter of the brain, ganglion cells, and RBCs. ...
C-Lipoproteins
• Definition: Lipoproteins are lipids combined with proteins in
the tissues. The lipid component is
phospho...
•
Plasma lipoproteins can be separated by two methods:
1. Ultra-centrifugation: Using the rate of floatation in sodium
chl...
a) Chylomicrons: They have the largest diameter and the

least density. They contain 1-2% protein only and 98-99% fat.
The...
d) High-density lipoproteins (HDL) or -Lipoproteins:
They contain 35-55% proteins in the form of
apolipoprotein A. They c...
Cholesterol:
• Importance: • It is the most important sterol in animal tissues as free
alcohol or in an esterified form (w...
Physical propeties:It has a hydroxyl group on C3, a double
bond between C5 and C6, 8 asymmetric carbon atoms and a
side ch...
• Chemical properties Intestinal bacteria reduce
cholesterol into coprosterol and dihydrocholesterol.
• - It is also oxidi...
• Ergosterol differs from 7-dehydrocholesterol in
the side chain. Ergosterol is converted to vitamin D2 by
irradiation wit...
Steroids
• Steroids constitute an important class of biological
compounds.
• Steroids are usually found in association wit...
• General consideration about naturally occurring steroids:
A typical member of this group is cholesterol. Certain facts h...
• Bile acids:
• They are produced from oxidation of cholesterol in the liver
producing cholic and chenodeoxycholic acids t...
CH 3
OH CH
3

OH

S o d iu m -ta u ro o r
g lyc o -c h o la te
R1

H2N

CH 2

C

R 1 or R 2

O

CH 3

HO

CH 3

COO - Na +...
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Transcript of "Fats"

  1. 1. FATS Dr. Daxaben N. Mehta Principal Smt. Sadguna C.U.Shah Home Science and C. U. Shah Arts & Commerce Mahila College, Wadhwancity, Dist: Surendranagar Home Science Fats
  2. 2. Fats • We all need some fat in our diet for energy. • Some fats are not good for us, like fried foods. • Only 10% of our diet should come from fat. Home Science Fats
  3. 3. Chemistry of Lipids Definition: • - Lipids are organic compounds formed mainly from alcohol and fatty acids combined together by ester linkage. H 2O O R CH 2 OH + Fatty alcohol HO C R Fatty acid E sterase (lipase) Home Science O R CH 2 O Fats C R ester (lipid)
  4. 4. Chemistry of Lipids • - Lipids are insoluble in water, but soluble in fat or organic solvents (ether, chloroform, benzene, acetone). • - Lipids include fats, oils, waxes and related compounds. • They are widely distributed in nature both in plants and in animals. Home Science Fats
  5. 5. Biological Importance of Lipids : 1. Palatable and storable to unlimited amount 2. High-energy value (25% of body needs), provide more energy per gram than carbohydrates and proteins 3. Supply the essential fatty acids 4. Supply the body with fat-soluble vitamins (A, D, E and K). 5. Important constituents of the nervous system. 6. Tissue fat is an essential constituent of cell membrane and nervous system, mainly phospholipids which are not affected by starvation. Home Science Fats
  6. 6. Biological Importance of Lipids 7-Stored lipids “depot fat” acts as: A store of energy. • A pad for the internal organs to protect from shocks. • A subcutaneous thermal insulator against loss of heat. 8-Lipoproteins, complex of lipids and proteins, important cellular constituents cellular and subcellular membranes. 9-Cholesterol , used for synthesis of adrenal cortical hormones, vitamin D3 and bile acids. 10- Lipids, bases for dealing with diseases such as obesity, atherosclerosis, lipid-storage diseases, essential fatty acid deficiency, respiratory distress syndrome, Home Science Fats
  7. 7. Classification of Lipids 1. 2. 3. 4. Simple lipids (Fats & Waxes) Compound or conjugated lipids Derived Lipids Lipid-associating substances Home Science Fats
  8. 8. Fatty alcohols 1-Glycerol: • Trihydric alcohol (i.e., containing three OH groups), popular name glycerin. • Synthesized in the body from glucose. Home Science Fats
  9. 9. Properties 1. Colorless viscous oily liquid with sweet taste. 2. On heating with sulfuric acid or KHSO4 (dehydration) it gives acrolein having bad odor, reaction used for detection of free glycerol or any compound containing glycerol. CH 2 HO OH CH CH CH 2 CHO 2 H 2O OH H e a tin g , K H S O 4 A c r o le in G ly c e r o l Home Science CH 2 Fats
  10. 10. Properties 3 Combines with three molecules of nitric acid trinitroglycerin (TNT) used as explosive and vasodilator. 4 On esterification with fatty acids it gives: • Monoglyceride or monoacyl-glycerol: one fatty acid + glycerol. • Diglyceride or diacyl-glycerol: two fatty acids + glycerol. • Triglyceride or triacyl-glycerol: three fatty acids + glycerol. 5 Nutritive value by conversion into glucose and enters in structure of phospholipids. Home Science Fats
  11. 11. Uses of Glycerol 1. Pharmaceutical and cosmetic preparations. 2. Reduces brain edema in cerebrovascular disease. 3. Nitroglycerin used as vasodilator especially for the coronary arteries, sed in treatment of angina pectoris. explosives manufacturing. 4. Glycerol is used in treatment of glaucoma (increased intraocular pressure)due to its ability to dehydrate the tissue from its water content. Home Science Fats
  12. 12. 2-Sphingosine • - It is the alcohol(monohydric) present in sphingolipids. • - It is synthesized in the body from serine and palmitic acid. • It is not positive with acrolein test. OH CH 3 (CH 2 ) 12 CH CH CH NH 2 CH 2 O H S p h in g o s in e Home Science CH Fats
  13. 13. Fatty Acids Definition: • Fatty acids are aliphatic mono-carboxylic acids mostly obtained from the hydrolysis of natural fats and oils. • Have the general formula R-(CH2)n-COOH and mostly have straight chain (a few exceptions have branched and heterocyclic chains). In this formula "n" is mostly an even number of carbon atoms (2-34) with a few exceptions that have an odd number. Home Science Fats
  14. 14. I. According to pre. or abs.of double bonds • A-Saturated Fatty Acids • they contain no double bonds with 2-24 or more carbons. • They are solid at room temperature except if they are short chained. • They may be even or odd numbered. • They have the following molecular formula, CnH2n+1COOH. Home Science Fats
  15. 15. Saturated fatty acids A-Short chain Saturated F.A. (2-10 carbon). a-Short chain Saturated volatile F.A.(2-6 carbon). b- Short chain Saturated non volatile F.A.(7-10 carbon). B-Long chain Saturated F.A.(more the10 carbon) Home Science Fats
  16. 16. Volatile short-chain fatty acids: They are liquid in nature and contain (1-6) carbon atoms. • water-soluble and volatile at room temperature, e.g., acetic, butyric, and caproic acids. • Acetic F.A. (2C ) CH3-COOH. • Butyric F.A. (4C ) CH3-(CH2)2-COOH. • Caproic F.A. (6C ) CH3-(CH2)4-COOH. Home Science Fats
  17. 17. Non-volatile short-chain fatty acids • They are solids at room temperature and contain 7-10 carbon atoms. • They are water-soluble and non-volatile at room temperature include caprylic and capric F.A. • caprylic (8 C ) CH3-(CH2)6-COOH. • Capric (10 C ) CH3-(CH2)8-COOH. Home Science Fats
  18. 18. Long-chain fatty acids • They contain more than 10 carbon atoms. • They occur in hydrogenated oils, animal fats, butter and coconut and palm oils. • They are non-volatile and water-insoluble • Include palmitic, stearic, and lignoceric F.A. (16C) CH3-(CH2)14-COOH • stearic (18 C ) CH3-(CH2)16-COOH • lignoceric (24C ) CH3-(CH2)22-COOH • palmitic Home Science Fats
  19. 19. Unsaturated Fatty Acids They contain double bond • monounsaturated they contain one double bonds . (CnH2n-1 COOH) • polyunsaturated they contain more the one double bond (CnH2n-more than 1 COOH). Home Science Fats
  20. 20. Monounsaturated fatty acids 1-Palmitoleic acid : • It is found in all fats. • It is C16:1∆9, i.e., has 16 carbons and one double bond located at carbon number 9 and involving carbon 10. CH3-( CH2 )5CH = CH-(CH2)7 –COOH Home Science Fats
  21. 21. Monounsaturated fatty acids 2-Oleic acid • Is the most common fatty acid in natural fats. • It is C18:1∆9, i.e., has 18 carbons and one double bond located at carbon number 9 and involving carbon 10. CH3-(CH2)7- CH=CH – (CH2)7-COOH Home Science Fats
  22. 22. Monounsaturated fatty acids 3-Nervonic acid (Unsaturated lignoceric acid). • It is found in cerebrosides. • It is C24:115, i.e., has 24 carbons and one double bond located at carbon number 15 and involving carbon 16. CH3 – (CH2)7 CH= CH – (CH2)13- COOH Home Science Fats
  23. 23. Polyunsaturated fatty acids (Essential fatty acids): • They are essential fatty acids that can not be synthesized in the human body and must be taken in adequate amounts in the diet. • They are required for normal growth and metabolism Home Science Fats
  24. 24. Polyunsaturated fatty acids • Source: vegetable oils , corn, linseed , peanut, olive, cottonseed, soybean and many other plant oils, cod liver oil and animal fats. • Deficiency: leads to nutrition deficiency disease. • Symptoms : poor growth and health with susceptibility to infections, dermatitis, decreased capacity to reproduce, impaired transport of lipids, fatty liver, and lowered resistance to stress. Home Science Fats
  25. 25. Function of Essential Fatty Acids 1. Useful in the treatment of atherosclerosis by transport of blood cholesterol, triglycerides and lowering it 2. Hormones are synthesized from them. 3. Enter in structure of all cellular and subcellular membranes and transporting plasma phospholipids. 4. Essential for skin integrity, normal growth and reproduction. 5. Important role in blood clotting (intrinsic factor). 6. Important in preventing and treating fatty liver. 7. Important role in health of the retina and vision. 8. They can be oxidized for energy production. Home Science Fats
  26. 26. Essential F A 1-Linoleic: 18:29, 12. • It is the most important since other essential fatty acids can be synthesized from it in the body. CH3-(CH2)4-CH = CH-CH2-CH=CH-(CH2)7COOH Home Science Fats
  27. 27. Essential F A 2-Linolenic acid: • C18:39, 12, 15, • in corn, linseed, peanut, olive, cottonseed and soybean oils. CH3-CH2-CH=CH-CH2-CH=CH-CH2-CH=CH-(CH2)7-COOH Home Science Fats
  28. 28. Essential F A 3-Arachidonic acid: • C20:45, 8, 11, 14. • It is an important component of phospholipids in animal and in peanut oil from which prostaglandins are synthesized. CH3-(CH2)4-CH=CH-CH2-CH=CH-CH2-CH=CHCH2-CH=CH-(CH2)3-COOH Home Science Fats
  29. 29. 1-Simple Lipids A-Neutral Fats and oils (Triglycerides) Definition: • Called neutral because they are uncharged due to absence of ionizable groups in it. • Neutral fats are the most abundant lipids in nature. They constitute about 98% of the lipids of adipose tissue, 30% of plasma or liver lipids, less than 10% of erythrocyte lipids. Home Science Fats
  30. 30. 1-Simple Lipids • Esterification of glycerol with one molecule of fatty acid gives monoglyceride, with 2 molecules diglyceride and with 3 molecules Triglycerides. O HO C O R1 CH 2 R2 + HO C O HO C O HO C F atty a c ids O R2 H CH 2 R3 OH OH C O C O C R1 H O H 2C 3 H 2O G lyce rol Home Science H 2C Fats O C R3 T rig lyce rid e s (T ria cylg lyce ro l)
  31. 31. Types of triglycerides 1-Simple triglycerides: Three fatty acids connected to glycerol are of same type the triglyceride is called simple triglyceride, e.g., tripalmitin. 2-Mixed triglycerides: if they are of different types, it is called mixed triglycerides, e.g., stearo-diolein and palmito-oleo-stearin. • Natural fats are mixtures of mixed triglycerides with a small amount of simple triglycerides. Home Science Fats
  32. 32. O CH 2 O CH 3 (C H 2 ) 14 C O C O C (C H 2 ) 14 CH 3 H O CH 2 O C (C H 2 ) 14 CH 3 T r ip a lm itin (s im p le tria c ylg ly c e r o l) O CH 2 O CH 3 (C H 2 ) 7 CH CH (C H 2 ) 7 C O C O C (CH 2 ) 16 CH 3 H O CH 2 O C (CH 2 ) 7 CH CH (CH 2 ) 7 1 -S te a ro -2 ,3 -d io le in (m ix e d tr ia c y lg ly c e ro l) O CH 2 O CH 3 (C H 2 ) 7 CH CH (CH 2 ) 7 C O C O C (C H 2 ) 14 H O CH 2 O C (C H 2 ) 16 1 -p a lm ito -2 -o le o -3 -s te a rin (m ix e d tr ia c y lg ly c e ro l) Home Science CH 3 Fats CH 3 CH 3
  33. 33. Fats & Oils • The commonest fatty acids in animal fats are palmitic, stearic and oleic acids. • The main difference between fats and oils is for oils being liquid at room temperature, whereas, fats are solids. • This is mainly due to presence of larger percentage of unsaturated fatty acids in oils than fats that has mostly saturated fatty acids. Home Science Fats
  34. 34. Physical properties of fat and oils: 1. Fats and oils are colorless, odorless and tasteless. Any color, or taste is due to association with other foreign substances, e.g., the yellow color of body fat or milk fat is due to carotene pigments(cow milk). 2. Specific gravity less than 1, they float on water. 3. Insoluble in water, but soluble in organic solvents as ether and benzene. 4. Melting points low, but higher than the solidification point, Home Science Fats
  35. 35. 1-Hydrolysis: Hydrolyzed into their constituents (fatty acids and glycerol) by the action of super heated steam, acid, alkali or enzyme (e.g., lipase of pancreas). • Enzymatic and acid hydrolysis glycerol and free fatty acids are produced. O O CH 2 O O R2 C O C C H 2C R1 L ip a s e o r A c id H HO C OH H O CH 2 O C R3 T ria cylg lyc e ro l Home Science 3 H 2O H 2C OH R1 C OH O + R 2 C OH O R3 C OH G lyce rol F re e fa tty a cid s Fats
  36. 36. 2-Saponification Alkaline hydrolysis produces glycerol and salts of fatty acids (soaps). • Soaps cause emulsification of oily material help easy washing of the fatty materials O O CH 2 O O R2 C O C C H 2C R1 HO H C OH H O CH 2 O C R3 T ria cylg lyc e ro l Home Science 3 NaOH H 2C OH R1 C ON a O + R 2 C ON a O R3 C ON a G lyce ro l S o diu m s a lts o f fatty a c id s (so a p ) Fats
  37. 37. 3-Halogenation • unsaturated fatty acids have the ability of adding halogens (e.g., hydrogen or hydrogenation and iodine or iodination) at the double bonds. • Important property to determine the degree of unsaturation of the fat or oil determines its biological value CH 3 (CH 2 ) 4 CH CH CH 2 CH CH (CH 2 ) 7 COO H L in o le ic a c id 2 I2 CH 3 (CH 2 ) 4 CH I CH I CH 2 CH I CH I S te a ra te -te tra -io d in a te Home Science Fats (CH 2 ) 7 COO H
  38. 38. 4-Hydrogenation or hardening of oils • Addition reactions accepting hydrogen at the double bonds of unsaturated fatty acids. • Hydrogenation done under high pressure of hydrogen and catalyzed by finely divided nickel or copper and heat. • It is the base of hardening of oils (margarine manufacturing), e.g., change of oleic acid of fats (liquid) into stearic acid (solid). • Advisable not to saturate all double bonds; margarine produced will be very hard, of very low biological value and difficult to digest. Home Science Fats
  39. 39. Advantages & Disadvantages 1. 2. 3. 4. • Advantage More pleasant as cooking fat. Digestible and utilizable as normal animal fats and oils. Less liable to cause gastric or intestinal irritation. Easily stored and transported and less liable to rancidity. Disadvantage fats include lack of fat-soluble vitamins (A, D, E and K) and essential fatty acids Home Science Fats
  40. 40. 5-Oxidation(Rancidty) • Toxic reaction of triglycerides leads to unpleasant odour or taste of oils and fats developing after oxidation by oxygen of air, bacteria, or moisture. • This is the base of the drying oils after exposure to atmospheric oxygen. Example is linseed oil, which is used in paints and varnishes manufacturing Home Science Fats
  41. 41. Rancidity • Physico-chemical change in the natural properties of the fat leading to the development of unpleasant odor or taste or abnormal color particularly on aging after exposure to atmospheric oxygen, light, moisture, bacterial or fungal contamination and/or heat. • Saturated fats resist rancidity more than unsaturated fats that have double bonds. Home Science Fats
  42. 42. Types and causes of Rancidity: 1. Hydrolytic rancidity 2. Oxidative rancidity 3. Ketonic rancidity 1-Hydrolytic rancidity: • • Results from slight hydrolysis of the fat by lipase from bacterial contamination leading to the liberation of free fatty acids and glycerol at high temperature and moisture. Volatile short-chain fatty acids have unpleasant odor. Home Science Fats
  43. 43. Hydrolytic rancidity O O O H 2 C OH CH 2 O C R 1 R2 C O C H Lipase HO C H O CH 2 O C R 3 Triacylglycerol Home Science 3 H 2O H 2 C OH R 1 C OH O + R C OH 2 O R3 C OH Glycerol Free fatty acids (volatile, bad odor) Fats
  44. 44. 2-Oxidative Rancidity Oxidation of fat or oil catalyzed by exposure to oxygen, light and/or heat producing peroxide derivatives which on decomposition give substances, e.g., peroxides, aldehydes, ketones and dicarboxylic acids that are toxic and have bad odor. • Occurs due to oxidative addition of oxygen at the double bond of unsaturated fatty acid of oils. Home Science Fats
  45. 45. Oxidative Rancidity P o ly u n s a tu ra te d fa tty a c id O x id a n t, O 2 P e r o x y ra d ic a l C y c lic p e r o x id e A ld e h y d e s s u c h a s m a lo n d ia ld e h y d e H y d ro p e ro x id e H y d ro x y fa tty a c id O th e r fra g m e n ts s u c h a s d ic a rb o x y lic a c id s Home Science Fats
  46. 46. 3-Ketonic Rancidity • It is due to the contamination with certain fungi such as Asperigillus Niger on fats such as coconut oil. • Ketones, fatty aldehydes, short chain fatty acids and fatty alcohols are formed. • Moisture accelerates ketonic rancidity. Home Science Fats
  47. 47. Prevention of rancidity 1. Avoidance of the causes (exposure to light, oxygen, moisture, high temperature and bacteria or fungal contamination). By keeping fats or oils in wellclosed containers in cold, dark and dry place (i.e., good storage conditions). 2. Removal of catalysts such as lead and copper that catalyze rancidity. 3. Addition of anti-oxidants to prevent peroxidation in fat (i.e., rancidity). They include phenols, naphthols, tannins and hydroquinones. The most common natural antioxidant is vitamin E that is important in vitro and in vivo. Home Science Fats
  48. 48. Hazards of Rancid Fats 1. The products of rancidity are toxic, i.e., causes food poisoning and cancer. 2. Rancidity destroys the fat-soluble vitamins (vitamins A, D, K and E). 3. Rancidity destroys the polyunsaturated essential fatty acids. 4. Rancidity causes economical loss because rancid fat is inedible. Home Science Fats
  49. 49. Analysis and Identification of fats and oils • Fat constants or numbers are tests used for: 1. Checking the purity of fat for detection of adulteration. 2. To quantitatively estimate certain properties of fat. 3. To identify the biological value and natural characteristics of fat. 4. Detection of fat rancidity and presence of toxic hydroxy fatty acids. Home Science Fats
  50. 50. 1-Iodine number • Definition: Number of grams of iodine absorbed by 100 grams of fat or oil. • Uses: Measure for the degree of unsaturation of the fat, as a natural property for it. • Unsaturated fatty acids absorb iodine at double bonds, so, as the degree of unsaturation increases iodine number and biological value of fat increase. • Used for identification of the type of fat, detection of adulteration and determining the biological value of fat. Home Science Fats
  51. 51. 2-Saponification number • Definition: Number of milligrams of KOH required to completely saponify one gram of fat. • Uses: Each carboxyl group of a fatty acid reacts with one mole of KOH during saponification, so, the amount of alkali needed to saponify certain weight of fat depends upon the number of fatty acids present per weight. • Fats containing short-chain acids will have more carboxyl groups per gram than long chain fatty acids and consume more alkali, i.e., will have higher saponification number. Home Science Fats
  52. 52. 3-Acids Number • Definition: • Number of milligrams of KOH required to neutralize the free fatty acids present in one gram of fat. • Uses: • Used for detection of hydrolytic rancidity because it measures the amount of free fatty acids present. Home Science Fats
  53. 53. 4-Reichert- Meissl Number • Definition: Number of milliliters of 0.1 N KOH required to neutralize the water-soluble fatty acids distilled from 5 grams of fat. Short-chain fatty acid (less than 10 carbons) is distillated by steam. • Uses: Studies the natural composition of the fat and used for detection of fat adulteration. • Butter that has high percentage of short-chain fatty acids has highest Reichert-Meissl number compared to margarine. Home Science Fats
  54. 54. 5-Acetyl Number • Definition: Number of milligrams of KOH needed to neutralize the acetic acid liberated from hydrolysis of 1 gram of acetylated fat (hydroxy fat reacted with acetic anhydride). • Uses: Natural or rancid fat that contains fatty acids with free hydroxyl groups are converted into acetylated fat by reaction with acetic anhydride. • Acetyl number is a measure of number of hydroxyl groups present. • Used for studying the natural properties of the fat and to detect adulteration and rancidity. Home Science Fats
  55. 55. 2-Compound Lipids Definition: • Lipids that contain additional substances, e.g., sulfur, phosphorus, amino group, carbohydrate, or proteins beside fatty acid and alcohol. • Compound or conjugated lipids are classified into the following types according to the nature of the additional group: 1. Phospholipids 2. Glycolipids. 3. Lipoproteins 4. Sulfolipids and amino lipids. Home Science Fats
  56. 56. A-Phospholipids Definition: Phospholipids or phosphatides compound lipids, Having phosphoric acid group in their structure. Importance: 1. Present in large amounts in the liver, brain and blood. Every animal and plant cell contains phospholipids. 2. The membranes bounding cells and subcellular organelles are composed mainly of phospholipids. Transfer of substances controlled by properties of phospholipids. 3. Important components of the lipoprotein coat essential for secretion and transport of plasma lipoprotein complexes. lipotropic agents that prevent fatty liver. 4. Myelin sheath of nerves is rich with phospholipids. Home Science Fats
  57. 57. A-Phospholipids 5-Important in digestion and absorption of neutral lipids and excretion of cholesterol in the bile. 6-Important function in blood clotting and platelet aggregation. 7-Provide lung alveoli with surfactants that prevent its irreversible collapse. 8-Important role in signal transduction across the cell membrane. 9-Phospholipase A2 in snake venom hydrolyses membrane phospholipids into hemolytic lysolecithin or lysocephalin. 10-They are source of polyunsaturated fatty acids for synthesis of eicosanoids. Home Science Fats
  58. 58. Sources & Structure They are found in all cells (plant and animal), milk and egg-yolk in the form of lecithins. 1. Fatty acids (a saturated and an unsaturated fatty acid). 2. Nitrogenous base (choline, serine, threonine, or ethanolamine). 3. Phosphoric acid. 4. Fatty alcohols (glycerol, inositol or sphingosine). Home Science Fats
  59. 59. Classification of Phospholipids • Classified into 2 groups acc. to type of alcohol present A- Glycerophospholipids: They are regarded as derivatives of phosphatidic acids 1. Phosphatidic acids. 2. Lecithins 3. Cephalins. 4. Plasmalogens. 5. Inositides. 6. Cardiolipin. B- Sphingophospholipids: They contain sphingosine as an alcohol and are named Sphingomyelins. Home Science Fats
  60. 60. A- Glycerophospholipids 1-Phosphatidic acids :Metabolic intermediates in synthesis of triglycerides and glycerophospholipids in the body function as a second messenger. They exist in two forms according to the position of the phosphate O  O P o ly u n s a t u r a te d R2 f a t t y a c id C O CH2 C  O C S a t u r a te d f a t t y a c id R1 H O  CH2 O P OH P h o s p h a te OH  - P h o s p h a t id i c a c i d O  O P h o s p h a te HO P O OH CH2 C  O C S a t u r a te d f a t t y a c id H O  R1 CH2 O C P o ly u n s a t u r a te d f a tt y a c i d R2  -P h o s p h a t i d ic a c id Home Science Fats
  61. 61. 2-Lecithins • Definition: Lecithins are glycerophospholipids contain choline as a base beside phosphatidic acid, exist in 2 forms α and β lecithins. Lecithins are a common cell constituent obtained from brain (α type), egg yolk (β type), or liver (both types). Lecithins are important in the metabolism of fat by the liver. • Structure: Glycerol is connected at C2 or C3 with a polyunsaturated fatty acid, at C1 with a saturated fatty acid, at C3 or C2 by phosphate to which the choline base is connected. The common fatty acids in lecithins are stearic, palmitic, oleic, linoleic, linolenic, clupandonic or arachidonic acids. Home Science Fats
  62. 62. Lysolecithin causes hemolysis of RBCs. This partially explains toxic the effect of snake venom,. The venom contains lecithinase, which hydrolyzes the polyunsaturated fatty converting lecithin into lysolecithin. Lysolecithins are intermediates in metabolism of phospholipids. O CH2 O R2 C O C O C R1 H CH3 O CH2 O P O CH2 OH C h o lin e  -L e c ith in CH3 CH3 + N CH3 CH2 C h o lin e O P CH2 Home Science O C O + CH3 CH3 C R1 H O OH  -L e c i th in N O O CH2 CH2 CH2 Fats O C R2
  63. 63. • Lung surfactant • Is a complex of dipalmitoyl-lecithin, sphingomyelin and a group of apoproteins called apoprotein A, B, C, and D. It is produced by type II alveolar cells and is anchored to the alveolar surface of type II and I cells. It lowers alveolar surface tension and improves gas exchange besides activating macrophages to kill pathogens. In premature babies, this surfactant is deficient and they suffer from respiratory distress syndrome. Glucocorticoids increase the synthesis of the surfactant complex and promote differentiation of lung cells. • • • • Home Science Fats
  64. 64. 3-Cephalins (or Kephalins): • Definition: They are phosphatidyl-ethanolamine or serine. Cephalins occur in association with lecithins in tissues and are isolated from the brain (Kephale = head). • Structure: Cephalins Home Science Fats
  65. 65. • Certain cephalins are constituents of the complex mixture of phospholipids, cholesterol and fat that constitute the lipid component of the lipoprotein “thromboplastin” which accelerates the clotting of blood by activation of prothrombin to thrombin in presence of calcium ions. O CH 2 O O R2 C O C C R1 H O CH 2 O P OH  -C e p h a lin O CH 2 CH 2 NH 2 HO HO CH 2 CH CH E th a n o la m in e COO H NH 2 CH COO H CH 3 NH 2 Home Science Fats S e rin e T h r e o n in e
  66. 66. 4-Plasmalogens: • Definition: Plasmalogens are found in the cell membrane phospholipids fraction of brain and muscle (10% of it is plasmalogens), liver, semen and eggs. • Structure: Plasmalogens resemble lecithins and cephalins in structure but differ in the presence of ,-unsaturated fatty alcohol rather than a fatty acid at C1 of the glycerol connected by ether bond. • At C2 there is an unsaturated long-chain fatty acid, however, it may be a very short-chain fatty acid Home Science Fats
  67. 67. • Properties: Similar to lecithins. CH 2 O R2 C O C O CH H CH 3 O CH 2 O P O CH 2 CH 2 N OH  -P la s m a lo g e n Home Science CH    -U n sa tu ra te d R 1 fa tty a lc o h ol + CH 3 CH 3 Fats
  68. 68. 5-Inositides: • Definition: • - They are phosphatidyl inositol. • Structure: They are similar to lecithins or cephalins but they have the cyclic sugar alcohol, inositol as the base. They are formed of glycerol, one saturated fatty acid, one unsaturated fatty acid, phosphoric acid and inositol O CH 2 O R2 C O C O C R1 H OH O CH 2 O P OH O 1 H  - P h o s p h a tid y lin o s ito l Home Science 2 H H 6 OH Fats OH 3 H OH H 5 H 4 OH
  69. 69. • Source: Brain tissues. • Function: • Phosphatidyl inositol is a major component of cell membrane phospholipids particularly at the inner leaflet of it. • They play a major role as second messengers during signal transduction for certain hormone.. • On hydrolysis by phospholipase C, phosphatidylinositol-4,5-diphosphate produces diacyl-glycerol and inositol-triphosphate both act to liberate calcium from its intracellular stores to mediate the hormone effects. Home Science Fats
  70. 70. 6-Cardiolipins: : • Definition They are diphosphatidyl-glycerol. They are found in the inner membrane of mitochondria initially isolated from heart muscle (cardio). It is formed of 3 molecules of glycerol, 4 fatty acids and 2 phosphate groups : • Function Used in serological diagnosis of autoimmunity OH diseases. O CH 2 O R2 C O C O C R1 H CH 2 H C OH O P O O H O CH 2 O P O CH 2 Home Science R4 C O OH C a rd io lip in CH 2 Fats O C O CH 2 C O R3 .
  71. 71. B-Sphingophospholipids 1-Sphingomyelins • Definition: Sphingomyelins are found in large amounts in brain and nerves and in smaller amounts in lung, spleen, kidney, liver and blood. • Structure: Sphingomyelins differ from lecithins and cephalins in that they contain sphingosine as the alcohol instead of glycerol, they contain two nitrogenous bases: sphingosine itself and choline. • Thus, sphingomyelins contain sphingosine base, one longchain fatty acid, choline and phosphoric acid. • To the amino group of sphingosine the fatty acid is attached by an amide linkage. Home Science Fats
  72. 72. • Ceramide This part of sphingomyelin in which the amino group of sphingosine is attached to the fatty acid by an amide linkage. • Ceramides have been found in the free state in the spleen, liver and red cells. C e ra m id e S p h in g o s in e F a tty a c id OH CH 3 (C H 2 ) 12 CH CH CH O CH NH C CH 2 C h o lin e O O P CH 3 O CH 2 OH CH 2 + N CH 3 P h o s p h a te S p h in g o m y e lin Home Science R1 Fats CH 3
  73. 73. B-Glycolipids : • Definition They are lipids that contain carbohydrate • residues with sphingosine as the alcohol and a very longchain fatty acid (24 carbon series). They are present in cerebral tissue, therefore are called cerebrosides • 1. 2. 3. Classification: According to the number and nature of the carbohydrate residue(s) present in the glycolipids the following are Cerebrosides. They have one galactose molecule (galactosides). Sulfatides. They are cerebrosides with sulfate on the sugar (sulfated cerebrosides). Home Science Fats Gangliosides. They have several sugar and sugaramine
  74. 74. 1-Cerebrosides: • Occurrence: They occur in myelin sheath of nerves and white matter of the brain tissues and cellular membranes. They are important for nerve conductance. • Structure: They contain sugar, usually -galactose and may be glucose or lactose, sphingosine and fatty acid, but no phosphoric acid. C e r a m id e S p h in g o s in e F a tty a c id OH CH 3 (C H 2 ) 12 CH CH CH O CH NH CH 2 CH 2 O H O OH H G a la c to s e OH H H H O OH H P s y c h o s in Home Science C e re b ro s id e Fats C R1
  75. 75. • Types: According to the type of fatty acid and 1. 2. 3. 4. carbohydrate present, there are 4 different types of cerebrosides isolated from the white matter of cerebrum and in myelin sheaths of nerves. Rabbit cerebrosides contain stearic acid. Kerasin contains lignoceric acid (24 carbons) and galactose. Cerebron (Phrenosin) contains cerebronic acid (2hydroxylignoceric acid) and galactose. Nervon contains nervonic acid (unsaturated lignoceric acid at C15) and galactose. Oxynervon contains oxynervonic acid (2hydroxynervonic acid) and galactose. Home Science Fats
  76. 76. 2-Sulfatides: • They are sulfate esters of kerasin or phrenosin in which the sulfate group is usually attached to the –OH group of C3 or C6 of galactose. Sulfatides are usually present in the brain, liver, muscles and testes. OH CH 3 (CH 2 ) 12 CH 2 CH CH O CH NH C CH 2 CH 2 O H OH O O H H H H OS O 3 H OH H S u lfa tid e s (s u lfa te d c e r e b r o s id e ) Home Science Fats R1
  77. 77. 3-Gangliosides: • They are more complex glycolipids that occur in the gray matter of the brain, ganglion cells, and RBCs. They transfer biogenic amines across the cell membrane and act as a cell membrane receptor. • Gangliosides contain sialic acid (N-acetylneuraminic acid), ceramide (sphingosine + fatty acid of 18-24 carbon atom length), 3 molecules of hexoses (1 glucose + 2 galactose) and hexosamine. The most simple type of it the monosialoganglioside,. It works as a receptor for cholera toxin in the human intestine. C e ra m id e -G lu co s e -G a lac tos e -N -a c e tylg ala c tos a m ine -G a la c tos e Sia lic a c id Home Science M on os ia log a ng lio s ide Fats
  78. 78. C-Lipoproteins • Definition: Lipoproteins are lipids combined with proteins in the tissues. The lipid component is phospholipid, cholesterol or triglycerides. The holding bonds are secondary bonds. • They include: 1. Structural lipoproteins: These are widely distributed in tissues being present in cellular and subcellular membranes. In lung tissues acting as a surfactant in a complex of a protein and lecithin. In the eye, rhodopsin of rods is a lipoprotein complex. • Transport lipoproteins: • These are the forms present in blood plasma. They are composed of a protein called apolipoprotein and different types of lipids. (Cholesterol, cholesterol esters, phospholipids and triglycerides). As the lipid content increases, the density of plasma lipoproteins decreases Home Science Fats
  79. 79. • Plasma lipoproteins can be separated by two methods: 1. Ultra-centrifugation: Using the rate of floatation in sodium chloride solution leading to their sequential separation into chylomicrons, very low density lipoproteins (VLDL or pre-lipoproteins), low density lipoproteins (LDL or lipoproteins), high density lipoproteins (HDL or lipoproteins) and albumin-free fatty acids complex. 2. Electrophoresis: is the migration of charged particles in an electric field either to the anode or to the cathode. It sequentially separates the lipoproteins into chylomicrons, pre--, -, and -lipoprotein and albumin-free fatty acids complex. P o la r lip id s (p h o s p h o lip id s) P o la r a p o lip o p ro te in s Hometru c tu re o f a S Science N o n p o la r lip id s (c h o le s te ro l a n d its e s te rs a n d tria c ylg lyc ero ls ) Fats p la s m a lip o p ro te in c o m p le x
  80. 80. a) Chylomicrons: They have the largest diameter and the least density. They contain 1-2% protein only and 98-99% fat. The main lipid fraction is triglycerides absorbed from the intestine and they contain small amounts of the absorbed cholesterol and phospholipids. b) Very low-density lipoproteins (VLDL) or pre-lipoproteins: Their diameter is smaller than chylomicrons. They contain about 7-10% protein and 90-93% lipid. The lipid content is mainly triglycerides formed in the liver. They contain phospholipid and cholesterol more than chylomicrons. c) Low-density lipoproteins (LDL) or -lipoproteins: They contain 10-20% proteins in the form of apolipoprotein B. Their lipid content varies from 80-90%. They contain about 60% of total blood cholesterol and 40% of total blood phospholipids. As their percentage increases, the liability to atherosclerosis increases. Home Science Fats
  81. 81. d) High-density lipoproteins (HDL) or -Lipoproteins: They contain 35-55% proteins in the form of apolipoprotein A. They contain 45-65% lipids formed of cholesterol (40% of total blood content) and phospholipids (60% of total blood content). They act as cholesterol scavengers, as their percentage increases, the liability to atherosclerosis decreases. They are higher in females than in males. Due to their high protein content they possess the highest density. e) Albumin-free fatty acids complex: It is a proteolipid complex with 99% protein content associated with long-chain free fatty acids for transporting them. Home Science Fats
  82. 82. Cholesterol: • Importance: • It is the most important sterol in animal tissues as free alcohol or in an esterified form (with linoleic, oleic, palmitic acids or other fatty acids). • Steroid hormones, bile salts and vitamin D are derivatives from it. • Tissues contain different amounts of it that serve a structural and metabolic role, e.g., adrenal cortex content is 10%, whereas, brain is 2%, others 0.2-0.3%. • Source: - It is synthesized in the body from acetyl-CoA (1gm/day, cholesterol does not exist in plants) and is also taken in the diet (0.3 gm/day as in, butter, milk, egg yolk, brain, meat and animal fat). Home Science Fats
  83. 83. Physical propeties:It has a hydroxyl group on C3, a double bond between C5 and C6, 8 asymmetric carbon atoms and a side chain of 8 carbon atoms. • It is found in all animal cells, corpus luteum and adrenal cortex, human brain (17% of the solids). • In the blood (the total cholesterol amounts about 200 mg/dL of which 2/3 is esterified, chiefly to unsaturated fatty acids while the remainder occurs as the free cholesterol. CH 3 CH 3 CH 3 CH 3 CH 3 HO Home Science C h o le s te r o l Fats
  84. 84. • Chemical properties Intestinal bacteria reduce cholesterol into coprosterol and dihydrocholesterol. • - It is also oxidized into 7-Dehydrocholesterol and further unsaturated cholesterol with a second double bond between C7 and C8. When the skin is irradiated with ultraviolet light 7-dehydrocholesterol is converted to vitamin D3. This explains the value of sun light in preventing rickets. CH 3 CH 3 CH 3 CH 3 CH 3 CH 3 CH 3 CH 3 HO HO H C op ro ste ro l, Home in fec e s Science H D ih ydroc h ole s te ro l, Fats in blo od a nd othe r tis su e s CH 3 CH 3
  85. 85. • Ergosterol differs from 7-dehydrocholesterol in the side chain. Ergosterol is converted to vitamin D2 by irradiation with UV Ergosterol and 7- dehydrocholesterol are called Pro-vitamins D or precursors of vitamin D. • - It was first isolated from ergot, a fungus then from yeast. Ergosterol is less stable than cholesterol (because of having 3 double bonds). CH 3 CH 3 CH 3 CH 3 CH 3 CH 3 CH 3 CH 3 HO HO 7 -d e hyd ro c ho les terol Home Science CH 3 CH 3 E rgo s te rol Fats CH 3
  86. 86. Steroids • Steroids constitute an important class of biological compounds. • Steroids are usually found in association with fat. They can be separated from fats after saponification since they occur in the unsaponifiable residue. • They are derivatives of cholesterol that is formed of steroid ring or nucleus. • 1. 2. 3. 4. 5. 6. Biologically important groups of substances, which contain this ring, are: Sterols. Adrenal cortical hormones. Male and female sex hormones. Vitamin D group. Bile acids. CardiacHome Science glycosides. Fats
  87. 87. • General consideration about naturally occurring steroids: A typical member of this group is cholesterol. Certain facts have to be considered when drawing steroid formula: 1) There is always oxygen in the form of hydroxyl or ketone on C3. 2) Rings C and D are saturated (stable). 3) Methyl groups at C18 C19. In case of vitamin D, the CH3 group at C19 becomes a methylene group (=CH2) and the ring B is opened, whereas, this methyl group is absent in female sex hormones (estrogens). 4) In estrogens (female sex hormones) ring A is aromatic and there is no methyl group on C10. 18 12 19 CH 3 2 HO 3 1 A 4 10 5 11 9 CH 3 13 C B 8 6 14 17 16 D 15 7 S te ro id r in g Home Science Fats
  88. 88. • Bile acids: • They are produced from oxidation of cholesterol in the liver producing cholic and chenodeoxycholic acids that are conjugated with glycine or taurine to produce glycocholic, glycochenodeoxycholic, taurocholic and taurochenodeoxycholic acids. They react with sodium or potassium to produce sodium or potassium bile salts. • Their function is as follows: 1. Emulsification of lipids during digestion. 2. Help in digestion of the other foodstuffs. 3. Activation of pancreatic lipase. 4. Help digestion and absorption of fat-soluble vitamins. 5. Solubilizing cholesterol in bile and prevent gall stone formation. 6. Choleretic action (stimulate their own secretion). 7. Intestinal antiseptic that prevent putrefaction Home Science Fats
  89. 89. CH 3 OH CH 3 OH S o d iu m -ta u ro o r g lyc o -c h o la te R1 H2N CH 2 C R 1 or R 2 O CH 3 HO CH 3 COO - Na + S o d iu m g lyc a te Home Science CH 3 O CH 3 OH HO S o d iu m -ta u ro o r g lyc o -c h en o d e o x yc h o la te R2 H 2N (CH 2 ) 2 C SO 3 - Na + S o d iu m ta u rate Fats R 1 or R 2
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