Lipids
Prof.Dr.Gülden Burçak
2011-2012
• Heterogenous group
• Insoluble in water, soluble in nonpolar
solvents
 Dietary constituents
 Adipose tissue
 Myelinated nerves
 Lipoproteins
• Obesity, diabetes mellitus, atherosclerosis
1)Simple lipids
Fats
Waxes
2)Complex lipids
Phospholipids
Glycolipids (glycosphingolipids)
Sulfolipids,aminolipids,lipoproteins
3)Precursor and derived lipids
Fatty acids, glycerol, steroids, other
alcohols, fatty aldehydes, ketone bodies,
hydrocarbons, lipid-soluble vitamins,
hormones
Simple lipids
• Fats : Esters of fatty acids with
glycerol
A fat in the liquid state : oil
• Waxes :Esters of fatty acids with
higher molecular weight monohydric
alcohols
• Uncharged lipids are called neutral
lipids
Acylglycerols
Cholesterol
Cholesteryl esters
Fatty acids
• Esterified and unesterified
• Even numbered, straight-chain
derivatives
• Saturated and unsaturated
Nomenclature
• -oic, -anoic, -enoic
• Numbered from the carboxyl carbon
(carbon no 1)
• α, ß, γ……………..ω ( terminal CH3 carbon)
• ∆ : number and position of double bonds
• ∆9 : double bond between C 9 and C10
• ω9 :double bond on C 9 counting from
the ωC ; ω9, ω6, ω3
Saturated fatty acids
Unsaturated fatty acids
• 1)Monounsaturated
• 2)Polyunsaturated
• 3)Eicosanoids
derived from eicosa (20C) polyenoic
fatty acids : prostanoids,leukotrienes
and lipoxins
Oleic acid
Essential fatty acids
• Linoleic acid (ω-6)
• α-Linolenic acid (ω-3)
• Arachidonic acid (ω-6) can be formed
from linoleic acid.
Geometric isomerism
Naturally occuring unsaturated fatty acids
are nearly all of cis configuration
L-shaped
A high number of cis double bonds leads to a
variety of possible spatial configurations
 Arachidonic acid with four cis double bonds has
kinks or U shape
 Spatial relationships in plasma membrane
phospholipids are important
 Trans fatty acids disturb the spatial
relationships
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• Melting point
Chain length
Degree of unsaturation
• Membrane lipids are more unsaturated
than storage lipids.
Eicosanoids
• Parent compound :C20 polyunsaturated fatty acids
• Physiologically and pharmacologically active
compounds
 Prostanoids
• prostaglandins (PGs)
• prostacyclins (PGIs)
• thromboxanes (TXs)
 Leukotrienes (LTs)
 Lipoxins (LXs)
• Prostaglandins cause contraction of smooth
muscle cells
• Prostacyclins are potent inhibitors of platelet
aggregation
• Thromboxanes cause vasoconstriction and
platelet aggregation
• Leukotrienes and lipoxins are potent
regulators of many disease processes
• Leukotrienes are potent proinflammatory
agents
Prostaglandin E2
Thromboxane A2
Leukotriene A4
Triacylglycerols : Storage
Mixed triacylglycerol
1,3-Distearopalmitin
Phospholipids
1) Phosphatidic acid and phosphatidyl
glycerol
2) Phosphatidylcholine
3) Phosphatidylethanolamine
4) Phosphatidylinositol
5) Phosphatidylserine
6) Lysophospholipids
7) Plasmalogens
8)Sphingomyelins
Phosphatidic acid
Phosphatidylcholines
• Most abundant in the plasma membrane
• Saturated acyl radical in C1 position and unsaturated
in the C2
• Choline: hepatic lipoprotein synthesis and export ;
acetyl choline
Dipalmitoyl lecithin
• Surface-active agent (surfactant) in the
lung
• Alveolar walls are not strong enough to
maintain their shape against the
surface tension of water.
• Dipalmitoyl lecithin and sphingomyelins
secreted to the lung chamber prevent
the adherence of the inner surfaces of
the alveoli
• Respiratory distress syndrome
Phosphatidylserine
Phosphatidylethanolamine
Phosphatidylinositol
Phosphatidylinositol 4,5-bisphosphate : a precursor of second messengers
Diphosphatidylglycerol (Cardiolipin)
Mitochondrial membranes
Lysolecithin
• Lysophospholipids : important in the metabolism
and interconversion of phosholipids.
• Phospholipase A2 : formation of a lysophospholipid
Plasmalogens
• Brain and muscle tissue
Sphingomyelins
• Brain and nerve tissue
Glycolipids
• In cell surface carbohydrates
• Particularly in the nervous tissue
• Glycosphingolipids
Galactosylceramide : neural tissues
Glucosylceramide : extraneural tissues
Galactosylceramide
(Galactocerebroside)
• Brain and other nervous tissue
• C24 : lignoceric, cerebronic , nervonic , oxynervonic acids
• Sulfogalactosylceramide (sulfatide) : myelin
Fatty acids in cerebrosides
Gangliosides
• Complex glycosphingolipids
Glucosylceramide + one or more sialic
acids
• Nervous tissue
Sialic acid : N-acetyl neuraminic acid
Neuraminic acid : 9 C sugar derived from mannosamine and
pyruvate
GM1 ganglioside :
Monosialoganglioside
Steroids
• The sterane ring
Cyclopentanoperhydrophenanthrene, a
tetracyclic hydrocarbon
• Steroid nucleus
Chair and boat conformation
Cis-trans configuration
Cholesterol
•Widely distributed in all cells, particularly in the nervous
tissue
•Plasma membrane and lipoproteins
•In animal fats
•Reduction of double bond : coprostanol (coprosterol)
Esterification of cholesterol at C3
Cholic acid : A cholesterol derivative
Steroid hormones
Ergosterol
A precursor of vitamin D
Isoprene and polyprenoids :
dolichol, ubiquinone
C95 alcohol
Plant derived isoprenoids
• Fat soluble vitamins
Vitamin A
Vitamin D
Vitamin E
Vitamin K
Adult reference ranges for lipids
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Total cholesterol : 140-200 mg/dL
HDL cholesterol : 40-75 mg/dL
LDL cholesterol : 50-130 mg/dL
Triglycerides : 60-150 mg/dL
Of total fatty acids 45 % in triglycerides, 35%
in phospholipids 15% in cholesterol esters and
5% as free fatty acids.
A lipoprotein molecule
Classification of plasma lipoproteins
Lipid Peroxidation
• Autooxidation of polyunsaturated fatty acids
(methylene interrupted double bonds)
• Initiated by free radicals,light, metal ions,
heme compounds, lipoxygenases
• ROO• , RO• and OH• radicals
• Deterioration of foods
• Tissue damage
Lipid peroxidation is a chain reaction
• Naturally occuring antioxidants vitamin E, uric
acid, vitamin C, beta carotene
• Catalase and peroxidases ; preventive
• Vitamin E and superoxide dismutase ; chain
breaking, trapping ROO• and O2⁻•
• Food additives : propyl gallate, butylated
hydroxyanisole (BHA) and butylated
hydroxytoluene (BHT)