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Classes of Lipids

fatty acids

triacylglycerols

phospholipids

Fat soluble vitamins

steroids

glycolipids*waxes

*

* fatty acids absent

eicosanoids

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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

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1.FATTY ACIDSGeneral structure

OO

C hydrophilic carboxyl group

hydrophobic hydrocarbon chain

Ionised at pH7 amphipathic

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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

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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

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Sperm Whale

Spermaceti organ