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1
Classes of Lipids
fatty acids
triacylglycerols
phospholipids
Fat soluble vitamins
steroids
glycolipids*waxes
*
* fatty acids absent
eicosanoids
2
Functions
• Energy source – storage compounds (triacyl glycerols)
• Hydrophobic barriers – membrane constituents (phospholipids &
glycoplipids)
• Functional– protective coverings (waxes)– regulatory properties e.g. coenzymes– hormones (steroids, prostaglandins,vitamins)– signalling e.g. odours
3
1.FATTY ACIDSGeneral structure
OO
C hydrophilic carboxyl group
hydrophobic hydrocarbon chain
Ionised at pH7 amphipathic
4
Aggregates of Fatty Acids
Surface film
micelle
Hydrophobic tail
Hydrophilic head
water
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SATURATED FATTY ACIDS
Typical example:stearic acid
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MONOUNSATURATED FATTY ACIDS e.g. OLEIC ACID - 18:1
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POLYUNSATURATED ACIDS
LINOLEIC ACID - 18:2
Both bonds are cis
8
Palmitic 16.0 StructuralPalmitoleic 16.1(9) lipids andStearic 18.0 triacylglycerolsOleic acid 18.1(9)
Acid name Symbol Function
Butyric 4:0Occur Capric 10.0 in milk
Lignoceric 24:0 Components of
Nervonic 24.1(15) cerebrosides
Linoleic 18.2 essential fattyLinolenic 18.3 acids
Arachidonic 20:4(5,8,11,14) Precursor of prostaglandins
predominant fatty acid residues in cells
Mp C
63.1
-0.5
69.6
13.4
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Link between metabolism of carbohydrates, fats and amino acids
AcetylCoA
TCA Cycle
Elongation
Desaturation
Various Fatty Acids
Sugars
Pyruvate
glycolysis
mitochondrion
Palmitic acid 16.0
Amino acids
AcetylCoA
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Synthesis of Fatty Acids: 2 carbon additions
Palmitate 16.0
Stearate 18.0
Oleate 18.1(9)
Linoleate 18.2 (9,12)
Linolenate 18.3 (9,12,15)
Arachidonate 20.4 (5.8.11.14)
EICONASOIDSOther poly unsaturated FA
elongation
desaturation
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Fatty acids: Summary
• General formula CH3 (CH2) nCOO• Amphipathic• Structure
– C16 -20 (biological)– unsaturated / mono or polysaturated– cis configuration – branching simple
• Rarely free
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TRIACYLGLYCEROL
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Adipocyte
nucleus
triacylglycerol
cytoplasm
10μm
14
Sperm Whale
Spermaceti organ