Medical Biochemistry
Molecular Principles of Structural Organization of Cells
3. LIPIDS
LIPIDS
• Organic compounds of biological nature
• Due to the predominence of hydrocarbon chains in their structure (-CH2CH2-CH2-), they have a hydrophobic nature which explains why
– they are insoluble or poorly soluble in water and
– soluble in nonpolar solvents (chloroform, ether, benzene).
Classification:
• depending on their physico-chemical properties (polarity):
– neutral, nonpolar (with no charge)
– polar (charged)
• depending on physiological importance:
– reserve – stored, used to supply energetic needs (acylglycerides)
– structural – used to buildup the biological membranes, protective layers in
plants, insects, skin of vertebrates;
Location: lipids represent 10-20% of the body mass (10-12 Kg) of which
– 98% is the reserve in the fat tissue,
– structural lipids (2-3 Kg) exist in membranes (40% of the dry weight); the richest
tissue in lipids is the nervous tissue (20-25%)
COMPONENTS OF LIPIDS
1. FATTY ACIDS (FA)
FA are derivatives of aliphatic hydrocarbons that contain – COOH
H H H
H H
H H
H H
l
l
l
l
l
l
l
l
l
l
l
l
l
l
l
l
H
H H H
H H
H H
l
l
l
l
l
l
l
l
l
l
l
l
l
l
l
l
l
l
H - C – C – C – C – C – C – C – C – C – C – C – C – C – C – C – C – C – COOH
H H H
H H
H H
H H
H H H H
H H
H
H
CH3-CH2-CH2-CH2-CH2-CH2-CH2-CH2-CH2-CH2-CH2-CH2-CH2-CH2-CH2-CH2-CH2- COOH
hydrocarbon chain
carboxyl
(nonpolar “tail”)
(polar”head”)
stearic acid
Physical properties:
• FA have an amphipatic nature (polar and nonpolar) and in biphasic systems
they orient with the polar end associated with water and the nonpolar end
associated with the hydrophobic phase (detergent–like)
• The melting point is related to
– chain length: the longer the chain - the higher the melting point,
– number of double bonds: the greater the number of doublebonds – the lower
the melting point
Classified in:
- Saturated
- Unsaturated
Saturated FA = zig-zag hydrocarbon chains with even number of C (12-18);
H2
C
H3C
H2
C
C
H2
H2
C
C
H2
H2
C
C
H2
H2
C
C
H2
H2
C
C
H2
H2
C
C
H2
COOH
C
H2
palmitic
16
hexadecanoic
CH3-(CH2)14-COOH
stearic
18
octadecanoic
CH3-(CH2)16-COOH
lignoceric
24
tetracosanoic
CH3-(CH2)22-COOH
-hydroxylignoceric
CH3-(CH2)21-CH(OH)-COOH
cerebronic 24
Chains with odd number of C exist occasionally, in small amounts in animal tissues.
Unsaturated FA (monoenic, dienic, trienic, tetraenic,…polyenic);
palmitoleic
acid
16:1
Δ9
CH3-(CH2)5-CH=CH-(CH2)7-COOH
oleic acid
18:1
Δ9
CH3-(CH2)7-CH=CH-(CH2)7-COOH
linoleic acid
(LA)
18:2
Δ9,12
α-linolenic
acid (ALA)
18:3
Δ9,12,15
arachidonic
acid (AA)
20:4
Δ5,8,11,14
CH3-(CH2)4-CH=CH-CH2-CH=CH-(CH2)7-COOH
CH3-CH2-CH=CH-CH2-CH=CH-CH2-CH=CH-(CH2)7-COOH
CH3-(CH2)4-CH=CH-CH2-CH=CH-CH2-CH=CH-CH2-CH=CH-(CH2)3COOH
Short-chain polyunsaturated fatty acids (SC-PUFA) LA and ALA can not be
synthesized by humans as they lack the enzymes required for their production.
–
–
–
–
–
They form the starting point for the production of long-chain FA (LC-PUFA)
Gamma-linolenic acid = GLA
(18:3)
Dihomo-gamma linolenic acid = DGLA
(20:3)
Arachidonic acid = AA
(20:4)
Eicosapentaenoic = EPA
(20:5)
Docosahexaenoic = DHA
(22:6)
– FA nomenclature:
• Δ system: palmitoleic acid: 16:1: Δ9
• systematic name:
– palmitoleic acid
= cis-Δ9-hexadecenoic acid
– oleic acid
= cis-Δ9-octadecenoic acid
– linoleic acid
= cis-Δ9 Δ 12-octadecadienoic acid
– linolenic acid
= cis-Δ9 Δ 12 Δ 15 -octadecatrienoic acid
– arachidonic acid
= cis-Δ5 Δ8 Δ 11 Δ 14-eicosatetraenoic
– FA are classified in 4 families depending on the number of C from the
terminal CH3 up to the first double bond :
• ω-3 linolenic acid (ALA)
CH3- CH2 -CH=CH-R
eicosapentaenoic (EPA)
docosahexaenoic (DHA)
• ω-6 linoleic acid (LA)
CH3-(CH2)4-CH=CH-R
gamma-linolenic acid (GLA)
dihomo-gamma linolenic acid (DGLA)
arachidonic acid (AA)
• ω-7 palmitoleic acid
CH3-(CH2)5-CH=CH-R
• ω-9 oleic acid
CH3-(CH2)7-CH=CH-R
FA with a double bond beyond C9 are not synthesized in the human body,
are “essential FA” or “vitamins F”: linoleic, linolenic, arachidonic acids
ω-9 are not essential in humans, because humans generally possess all the
enzymes required for their synthesis
PROSTAGLANDINS (PG)
• Hormone-like compounds:
– synthesized at need, in small amounts, starting from arachidonic acid,
– with short life,
– exert a local action at the site of formation
• Location:
– first isolated from prostate;
– they can occur in all cells and organs except erythrocytes
• Structure: derived from C20-polyene FA, containing a
cyclopentane ring;
– depending on the type and number of oxygen substituents and
location of double bonds in the cyclopentane ring they have several
types: A, B, C, D, E, F, G, H;
– depending on the number of double bonds in the side chains, they are:
PGE1, PGE2, PGE3 or PGF1, PGF2, etc
• Prostaglandins action
• In the endocrine glands :
– adrenal glands – stimulate the formation of steroid hormones and secretion of
catecholamines
– thyroid gland – synthesis of iodothyronines
– pancreas – the release of insulin
• Control of smooth muscles of bronchi, intestine, uterus (cGMP, Ca2+)
– Bronchi muscles contracted by PGD2, PGG2, PGH2 and relaxed by PGE
– Blood vessels muscles are contracted by PGF2 and relaxed by PGE2 (influence
the blood pressure)
– PGE2 increases the volume of urinary discharge and Na+ concentration in urine
– PGF2 stimulates the contraction of uterus and fallopian tubes, increases the
involution of corpus luteum, facilitating the birth
– PG intensify the intestinal motility
• The gastric juice secretion is inhibited by PGE and stimulated by PGF2
The disturbance of production may determine inflammation, thrombosis,
gastric ulcer or may prevent the ulcer of intestinal or gastric mucosae.
PGF2 (dinoprost) is used in obstetric practice for pregnancy termination
PGE2 (dinoprostone) is used to stop the bronchi spasm, treat hypertension or
peptic ulcer
THROMBOXANES (TX)
• Structure:
– analogs of prostanoic acid with a six-membered ring containing
oxygen,
– the different capital letters designate the combinations of the
ring substituents,
– the number shows the number of unsaturated bonds
• Functions:
– TXA2 is produced by platelets causing contraction of the arteries
and triggering the platelet aggregation, an opposite action to
PGI2 (prostacyclin) produced by the endothelial cells of the
vascular system (balanced working)
HYDROPEROXYEICOSATETRAENOIC ACIDS (HPETEs)
• Hydroxy-FA derivatives of arachidonic acid, with no ring structure
• Function – they can be converted in active compounds such as
leukotrienes.
LEUKOTRIENES (LT)
• Formed from HPETEs by lipooxygenase,
• Structure:
– have 3 conjugated double bonds (those formed from arachidonic
acid have 4),
– an additional letter shows the modification to the carbon chain
(LTA4, LTB4),
• Functions: involved in chemotaxis, inflammation, allergic reactions
– LTD4 = the slow-reacting substance of anaphylaxis (SRS-A) which
causes the contraction of smooth muscle of bronchi, blood vessels,
coronary arteries
– LTB4 attracts the neutrophils and eosinophils at the site of
inflammation
2. ALCOHOLS
• Aliphatic alcohols without nitrogen
–
Glycerol
CH2 - OH
l
CH - OH
l
–
Higher aliphatic alcohols: stearylic alcohol
CH2 - OH
CH3-(CH2)16-CH2- OH
–
–
–
–
Ethanolamine = colamine
Choline
Serine
Sphingosine CH - (CH ) - CH = CH - CH - OH
3
2 12
HO- CH2-CH2-NH2
HO- CH2-CH2-N+(CH3)3
HO- CH2-CH(COOH)-NH2
Dihydrosphingosine CH - (CH ) -CH -CH - CH - OH
3
2 12
2
2
• Aliphatic alcohols with nitrogen (aminoalcohols)
CH - NH2
CH - NH2
CH 2 - OH
CH 2 - OH
• Cyclic alcohols:
–
Inositol
H
OH
–
OH
OH
H
OH
H
H
OH
H
H
OH
Sterols
• Steroids = compounds containing a hydrocarbon skeletal framework as that of gonane
(sterane); those which contain a hydroxyl group and can form esters are named sterols
• Origin:
– animal – zoosterols; e.g. cholesterol
– plant – fitosterols; e.g. β-sitosterol
12
11
CHOLESTEROL
1
10
2
A
13
14
B
16
D
C
9
17
15
8
7
3
5
4
6
HO
• Exists in mammalian tissues free or esterified.
• Location:
–
–
–
–
nervous tissue (only free),
adrenal glands (>80% esterified),
liver,
serum (70-80% esterified)
• Structural lipid – part of cell membrane (more than the
membranes of mitochondria, microsomes, nuclei),
influencing the membrane fluidity
• Cholesterol functions:
OH
– In the liver:
COOH
• oxidation of the side chain results in bile acids
•
•
•
•
(cholic and deoxycholic acids = primary bile acids);
they are conjugated with glycine or taurine forming
glycocholic acid or taurocholic acid
eliminated in the bile as bile salts (sodium or
potassium glycocholate or taurocholate).
chenodeoxycholic and lithocholic are secondary bile
acids formed in the intestine (bacterial enzymes)
The bile salts are amphypatic molecules with
surface-active properties, favoring the emulsification
of lipids in the intestine; they assist the absorption
of fat-soluble vitamins. The low solubility may favor
the formation of gall stones.
– Synthesis of steroid hormones in
• adrenal glands (glucocorticoid, mineralcorticoid)
• testis (testosterone),
• ovary (estradiol, progesterone),
• placenta (progesterone).
– Steroid vitamins (vitamins D)
HO
OH
Cholic acid
OH
COOH
HO
Deoxycholic acid
COOH
HO
Chenodeoxycholic acid
COOH
Lithocholic acid
OH
OH
OH
COOH
HO
OH
CO-NH-CH 2-CH 2-SO 3-Na +
CO-NH-CH 2-CH 2-SO 3H
HO
OH
HO
taurocholic acid
cholic acid
OH
sodium taurocholate
OH
OH
CO-NH-CH 2-COOH
HO
OH
CO-NH-CH 2-COO -Na+
HO
OH
glycocholic acid
sodium glycocholate
BILE ACID
CONJUGATED BILE ACID
BILE SALTS
CLASSIFICATION OF LIPIDS
I.HOMOLIPIDS
(SIMPLE LIPIDS)
- esters composed of
lipid monomers
- fatty acids + alcohols
- ester bonds
1. GLYCERIDES
or ACYLGLYCERIDES
(esters of fatty acids with tribasic alcohol: glycerol)
2. STERIDS
(esters of fatty acids with sterols)
3. WAXES
(esters of fatty acids with higher monobasic alcohols)
LIPIDS
with N
II.HETEROLIPIDS
(COMPLEX LIPIDS)
- ester or amide bonds
1. GLYCEROPHOSPHOLIPIDS
(PHOSPHOLIPIDS)
- all contain P
- alcohol: glycerol
- ester bonds
without N
with P
2. SPHINGOLIPIDS
- all contain N
- alcohol: sphingosine
- amide bonds
without P
LECYTINES
CEPHALINES
SERINCEPHALINES
PLASMALOGENS
PHOSPHATIDIC ACIDS
PHOSPHATIDYL-INOSITOL
CARDIOLIPINS
SPHINGOMYELINS
CERAMIDES
CEREBROSIDES
SULPHOLIPIDS
GANGLIOSIDES
I. SIMPLE LIPIDS
1. ACYLGLYCERIDES
• Esters of glycerol with fatty acids
• Neutral lipids
• Classified in mono-, di-, tri-glycerides containing 1, 2, 3 acyl (R-CO-):
– simple acylglycerides: residues of the same FA (R1=R2=R3)
– complex acylglycerides: residues from different FA
CH2 – OH
l
CH – OH
l
CH2 – OH
glycerol
HO-CO-R1
+
HO-CO-R2
HO-CO-R3
fatty acids
-3H2O
CH2 – O – CO - R1
l
CH – O – CO - R2
l
CH2 - O – CO - R3
triglyceride (TG)
• Natural neutral lipids are almost exclusively triglycerides
(TG); mono- and di-acylglycerides are formed in the intestine
during the digestion and absorption.
CH 2 - O - CO - R1
CH 2 - O - CO - R1
CH 2 - O - CO - R1
CH - OH
CH - O - CO - R2
CH - O - CO - R2
CH 2 - OH
CH 2 - OH
CH 2 - O - CO - R3
monoacylglyceride
diacylglyceride
triacylglycerides
• Natural fats are mixtures of simple and complex TG, with the
•
prevalence of unsaturated TG.
In the human body they contain:
–
–
–
–
–
oleic acid
palmitic acid
linoleic acid
palmitoleic acid
stearic acid
45%,
25%,
8%,
7%,
6%
• Physico-chemical properties:
– The melting point increases with proportion of saturated fatty acids
– Less dense than water
– Soluble in nonpolar solvents; only mono and diglycerides are water
soluble (contain free -OH) forming micelles in water; TG do not.
– Basic hydrolysis (saponification) → glycerol + free fatty acids salts
CH2 - O - CO - R1
CH - O - CO - R2
CH2 - OH
+ 3KOH
CH2 - O - CO - R3
CH - OH
R1-COOK
+
R2-COOK
R3-COOK
CH2 - OH
– In the organism, the hydrolysis is catalyzed by lipase
CH 2 - O - CO - R1
CH - O - CO - R2
CH 2 - O - CO - R3
CH 2 - OH
+ 3 H2O
CH - OH
CH 2 - OH
R1-COOH
+
R2-COOH
R3-COOH
I. SIMPLE LIPIDS
2. STERIDS
R-OC-O
•
•
•
•
Esters of cholesterol with fatty acid
Exist in products of animal origin (butter, egg yolk)
In the human tissue cholesterides = 75% of total cholesterol
In the blood enter in the structure of lipoproteins
I. SIMPLE LIPIDS
3. WAXES
• Mixtures of ethers and esters of higher monobasic alcohols
and higher fatty acids, usually
– cetylic alcohol
– stearylic alcohol
CH3-(CH2)14-CH2-OH
CH3-(CH2)18-CH2-OH
CH3 -(CH2)14-COOH + CH3-(CH2)14-CH2-OH
CH3-(CH2)14-CO-O-CH2 -(CH2)14-CH3
- H2O
palmitic acid
•
cetylic alcohol
cetylic palmitate
They are products of the animal or plant epidermis, serve as
protective film against water loss or wetting (high
hydrophobic): e.g. leaves and fruits, skin and hair, feathers,
skeleton of insects, honey wax.
Energy reserve material (marine animals)
II. COMPLEX LIPIDS (HETEROLIPIDS)
1. PHOSPHOLIPIDS
• Complex lipids representative of phosphate-substituted
•
•
•
•
esters of diverse organic alcohols.
Are polar lipids
Predominantly contained in the membranes, structural
components of organs, mainly in brain and nerves
Take part in metabolic processes: involved in intestinal fat
resorption, fatty acid transport and oxidation, fatty infiltration
of the liver, blood coagulation, prostaglandin synthesis
Classified in:
– phosphoacylglycerides
– sphingolipids
II. COMPLEX LIPIDS (HETEROLIPIDS)
1. PHOSPHOLIPIDS (PHOSPHOACYLGLYCERIDES)
CH 2 - O - CO - R1
nonpolar, hydrophobic
CH - O - CO - R2
CH 2 - O - P - X
amphipatic structure
polar, hydrophylic
OH O
• Structure:
•
The alcohol = glycerol
– the –OH in C1 is esterified with a saturated FA
nonpolar
– the –OH in C2 is esterified with an unsaturated FA (trans)
hydrophobic
– the –OH in C3 forms an phosphoester bond with a H3PO4
polar
– X is an alcohol residue
hydrophylic
= amphipatic character
which makes them easily soluble in nonpolar solvents and in water forming micelles
(the hydrophobic radicals oriented to the inner hydrophobic zone; the hydrophylic
groups are located on the outer surface toward the aqueous phase)
They bear both negatively and positively charged groups = amphoteric character
1. PHOSPHOLIPIDS (PHOSPHOACYLGLYCERIDES)
1.1. With N
1.1.1. Lecithins (phosphatidylcholines)
– Structure: FA = oleic, palmitic, stearic acids, (in brain poliunsaturated, > 20 C)
X = choline
HO-CH2-CH2-N+(CH3)3
the –OH is ionized and associated with K+, Na+, Ca2+
– Location: membranes (50% of lipids in membrane)
1.1.2. Cephalins (phosphatidyletanolamines)
– Structure: FA = oleic, stearic
X = ethanolamine=cholamine
HO-CH2-CH2-NH2
– Location: intracellular membranes of animal cells (20%) in all tissues, blood lipoproteins;
in plants, microorganisms
1.1.3. Serincephalins (phosphatidylserines)
– Structure: X = serine
– Location: most animal tissue (brain)
1.1.4. Plasmalogens
– Structure: the –OH in C1 forms an ether bond with an acetal
X = colamine
– Location: all tissues, mainly in brain and spinal cord (50-90%)
HO-CH2-CH-NH2
│
COOH
HO-CH=CH-CH2-R1
HO-CH2-CH2-NH2
1. PHOSPHOLIPIDS (PHOSPHOACYLGLYCERIDES)
1.2. Without N
1.2.1. Phosphatidic acids
– Structure: X = OH
– Location small amounts in animal tissues, intermediary metabolite
1.2.2. Phosphatidyl inositol
– Structure: X = inositol (with 1-2 –OH groups esterified with H3PO4)
– Location: brain, liver, heart; important in myelin sheets with a high turnover rate;
they are bound with proteins
1.2.3. Cardiolipins
– Structure:
• FA = oleic acid and linoleic acid (1:5)
• X = phosphatidylglycerol
– Location: heart, animal tissues, mainly in the mitochondria membranes
Lecitines
(Phosphatidyl-
CH 2 - O - CO - R1
CH - O - CO - R2
choline)
CH 2 - O - CO - R1
CH - O - CO - R2
CH 2 - O - P - OH
CH 2 - O - P - O - CH2-CH2-N(CH 3)3
OH O
OH O
CH 2 - O - CO - R1
CH 2 - O - CO - R1
Cefalines
CH - O - CO - R2
CH 2 - O - P - O- CH2-CH 2-NH 2
CH - O - CO - R2
(Phosphatidylethanolamine)
Phosphatidylinositol
CH 2 - O - P - O
OH O
OH O
CH 2 - O - CO - R1
Serincefalines
CH - O - CO - R2
CH 2 - O - P - O - CH2-CH-NH 2
OH O
Phosphatidic acid
(Phosphatidylserine)
H
OH
OH
H
OH
H
H
H
OH
H
OH
COOH
O
CH 2 - O - CH = CH - (CH2)13 - CH3
CH 2 - O - CO - R1 CH2 - O - P - O - CH2
CH - O - CO - R2
CH - O - CO - R2
CH - OH
CH - O - CO - R3
CH 2 - O - P - O
CH 3
CH2 - O - CO - R4
CH 2 - O - P - O- CH2-CH 2-NH 2
OH O
OH
Plasmalogens
OH O
Cardiolipins
2. SPHINGOLIPIDS
CH3 - (CH2)12 - CH = CH - CH - OH
CH - NH - CO - R
• Structure:
CH2 - X
– alcohol = sphingosine
– R = FA with 24 C (lignoceric, cerebronic, nervonic, hydroxynervonic)
– amide bond between the NH2 group of sphingosine and the FA
• Classification:
2.1. With P – Sphingomyelins
– Structure: X = phosphorylcholine or phosphorylcolamine
– Location: nerve tissue white matter (myelin sheath), lungs,
liver, kidney, spleen, blood (erythrocyte membrane)
CH3 - (CH2)12 - CH = CH - CH - OH
CH3 - (CH2)12 - CH = CH - CH - OH
CH - NH - CO - R
CH - NH - CO- R
CH 2 - O - P - O-CH2-CH 2-NH 2
CH 2 - O - P - O-CH2-CH 2-NH 3
O
O
HO
O
2. SPHINGOLIPIDS
2.2.Without P
2.1.1. Ceramides
– Structure: X = OH
Glycosphingolipids contain carbohydrate moieties; they exist in animal tissues in large
amount, especially in neurons (normal electric activity and transmission of nervous
impulse):
2.1.2. Cerebrosides
– Structure: X = β-galactose (or rarely β-glucose)
– Location: brain
2.1.3. Sulfatides (sulfolipids)
– Structure: X = Galactose-2-sulfate
– Acidic properties, easily binding cations (transport across the membranes), necessary for
the normal electric activity of the neurons
– Location: white and grey matter of nervous tissue (myelin), liver, kidneys, epidemis, hair,
nails (a sulfatide with sialic acid)
2.1.4. Gangliosides
– Structure:
• FA = stearic ascid 86-95%, palmitic acid, arachidic acid
• X = olygoglucide composed of monoses and N-acetylneuraminic acid (NANA)= sialic acid
– Location : cerebral cortex cells, ganglion cells of CNS, membranes of cells in liver, spleen,
erythrocytes
CH3 - (CH2)12 - CH = CH - CH - OH
CH - NH - CO - R
ceramides
CH2 - OH
CH3 - (CH2 )12 - CH = CH - CH - OH
CH3 - (CH2)12 - CH = CH - CH - OH
CH - NH - CO - R
CH - NH - CO - R
CH 2 - O
CH 2 - O
CH 2 -OH
CH 2 -OH
O
OH
H
OH
H
OH
H
H
H
H
OH
cerebrosides
O
OH
H
H
H
H
O - SO3H
sulfatides
SPHINGOLIPIDOSES
= inherited genetic disorders (lipid storage diseases) due to a
deficiency of an enzyme that is involved in the normal
catabolism of a particular sphingolipid resulting in the
intracellular accumulation of that lipid
Disease
•
•
•
•
Nyemann-Pick
Gaucher’s
Krabbes’s
Metachromatic
leukodystrophy
• Fabry’s
• Tay-Sachs
Lipid accumulated
sphingomyelin
glucocerebroside
galactocerebroside
sulfo-Gal-cerebroside
Primary organ
affected
brain, liver, spleen
brain, liver, spleen
brain
brain
ceramide trihexoside
ganglioside GM1
kidneys
brain
MAIN BIOLOGICAL FUNCTIONS OF LIPIDS
1.
2.
Energetic (1g → 9.3 kcal) – FFA, TG,
Structural (cell membranes) - C, CE, phosphoglycerides,
sphingomyelins,
3. Emulsifying due to amphipatic character - phosphoglycerides, bile acids
4. Dissolving of lipid-soluble compounds (vitamins) in intestine - bile
acids, sterols
5. Transport (cations across the membranes) - phosphoglycerides,
sphingomyelins
6. Electric insulation (myelin sheath) - sphingomyelins
7. Mechanical (protection of internal organs) - TG
8. Heat-insulation (subcutaneous tissue) - TG
9. Hormonal - steroid hormones, PG
10. Vitaminogenic - linoleic, linolenic, arachidonic acids
H2
C
H3C
H2
C
H3C
7
H2
C
C
H2
H2
C
H2
C
C
H2
C
H2
H2
C
H2
C
H2
C
C
H2
C
H2
H2
C
H2
C
H2
C
C
H2
H2
C
C
H2
H2
C
C
H2
C
H2
H
C
H2
C
H2
C
H2
C
C
H2
C
H2
H2
C
H2
C
H2
C
C
H2
C
H2
H2
C
H2
C
COOH
C
H2
Palmitic acid
16
COOH
C
H2
Stearic acid
18
COOH
H3C
C
C
C
C
C
C
C
H2
H
H
H
H
2
H
H2
2
2
2
H2
H2
H2
H2
H
H
H
H
2
2
2
9
C
C
C
C
C
C
C
C
COOH
H3C
C
C
C
C
C
C
C
C
H2
H2
H2
H
H2
H2
H
H2
2
6 H2
H2
H
H2
H2
H
2
H2
H
C
C
C
C
C
C
C
C
COOH
H3C
C
C
C
C
C
C
C
C
3 H2 H2 H H2 H H H2 H H H2 H2 H2 H2 H2 H2 H2
C
C
C
C
C
C
C
C
COOH
H3C
C
C
C
C
C
C
C
C
H
H2
H
CH
H2
H
H
H2
2
2
6 H2
H2
H2
H
H
H
H
H
2
H
2
C
C
C
C
C
C
C
C
C
COOH
H3C
C
C
C
C
C
C
C
C
C
H2
H2
H
H
H2
H
H
H2
H2
Palmitoleic acid
16:Δ9
Oleic acid
18: Δ9
Linoleic acid
18: Δ9,12
Linolenic acid
18: Δ9,12,15
Arachidonic acid
20: Δ5,8,11,14