2013 W. H. Freeman and Company. 10 Lipids

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1 2013 W. H. Freeman and Company 10 Lipids

2 Storage lipids: TG lipid 의기능 : 1 Energy source 3 Electrical insulator 2 Thermal insulator 4 Membrane 의구성성분, 방수, 부력, cofactor, signaling 등 지방대사이상 : obesity, atherosclerosis, metabolic syndrome 1) 지방산 (fatty acid, FA) 의종류 1 지방산 : carboxylic acid 탄화수소사슬 : Hydrophobic + Hydrophilic 2 필수지방산 CH 3 -CH 2 COOH a) Linoleic acid 18:2( 9,12 -terminus c-terminus ) 식용유, ω 6 FA ( 1 ) ( 1, n-1) b) -Linolenic acid 18:3( 9,12,15 ) 들깨, ω 3 FA c) Arachidonic acid 20:4( 5,8,11,14 ), ω 6 FA 3 Eicosapentaenoic acid(epa) 20:5( 5,8,11,14,17 ), DHA 등푸른생선 ω 3 FA 4 Oleic acid 18:1( 9 ) 올리브유, ω 9 FA

3 Lipids: Structurally Diverse Class Organic molecules that are characterized by low solubility in water, that is, are relatively hydrophobic.

4 Biological Functions of Lipids Storage of energy Reduced compounds: lots of available energy Hydrophobic nature: good packing Insulation from environment Low thermal conductivity High heat capacity (can absorb heat) Mechanical protection (can absorb shocks) Water repellant Hydrophobic nature: keeps surface of the organism dry Prevents excessive wetting (birds) Prevents loss of water via evaporation Buoyancy control and acoustics in marine mammals Increased density while diving deep helps sinking (just a hypothesis) Spermaceti organ may focus sound energy: sound stun gun?

5 More Functions Membrane structure Main structure of cell membranes Cofactors for enzymes Vitamin K: blood clot formation Coenzyme Q: ATP synthesis in mitochondria Signaling molecules Paracrine hormones (act locally) Steroid hormones (act body wide) Growth factors Vitamins A and D (hormone precursors) Pigments Color of tomatoes, carrots, pumpkins, some birds Antioxidants Vitamin E

6 Classification of Lipids Based on the structure and function Lipids that do not contain fatty acids: cholesterol, terpenes, Lipids that contain fatty acids (complex lipids) can be further separated into: storage lipids and membrane lipids

7 Fatty Acids Carboxylic acids with hydrocarbon chains containing between 4 to 36 carbons Almost all natural fatty acids have an even number of carbons Most natural fatty acids are unbranched Saturated: no double bonds between carbons in the chain Monounsaturated: one double bond between carbons in the alkyl chain Polyunsaturated: more than one double bond in the alkyl chain

8 Fatty Acid Nomenclature Omega 3 fatty acids are essential nutrients Humans need them but cannot synthesize them Including ALA, DHA, and EPA Although DHA and EPA can be synthesized from ALA (oleic acid)

9 권장섭취 : Omega 6 FA:3 FA=1:1~4:1 >>> 에스키모인, 지중해식단북미인 : Omega 6 FA:3 FA=10:1~30~:1: >>> 심장병, 뇌졸중다발

10 Fatty Acid Nomenclature Palm oil Olive oil ( 올리브유 ) Flaxeed oil ( 아마씨유 ) Perilla oil( 들깨유 ) Soybean oil( 식용유 )

11 Lipid peroxidation MDA

12 Solubility and Melting Point of Fatty Acids Solubility decreases as the chain length increases Melting Point decreases as the chain length decreases decreases as the number of double bonds increases

13 Conformation of Fatty Acids The saturated chain tends to adopt extended conformations The double bonds in natural unsaturated fatty acids are commonly in cis configuration, which kinks the chain

14 Melting Point and Double Bonds Saturated fatty acids pack in a fairly orderly way extensive favorable interactions Unsaturated cis fatty acid pack less orderly due to the kink less extensive favorable interactions It takes less thermal energy to disrupt disordered packing of unsaturated fatty acids: unsaturated cis fatty acids have a lower melting point

15 Trans Fatty Acids Trans fatty acids form by partial dehydrogenation of unsaturated fatty acids Done to increase shelf life or stability at high temperature of oils used in cooking (especially deep frying) A trans double bond allows a given fatty acid to adopt an extended conformation Trans fatty acids can pack more regularly and show higher melting points than cis forms Consuming trans fats increases risk of cardiovascular disease Avoid deep frying partially hydrogenated vegetable oils Current trend: reduce trans fats in foods (Wendy s, KFC)

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18 Triacylglycerols (Nonpolar) Majority of fatty acids in biological systems are found in the form of triacylglycerols Solid ones are called fats Liquid ones are called oils The primary storage form of lipids (body fat) Less soluble in water than fatty acids due to the lack of charged carboxylate group Less dense than water: fats and oils float

19 Triacylglycerols

20 Fats Provide Efficient Fuel Storage The advantage of fats over polysaccharides: Fatty acids carry more energy per carbon because they are more reduced Fatty acids carry less water per gram because they are nonpolar Glucose and glycogen are for short term energy needs, quick delivery Fats are for long term (months) energy needs, good storage, slow delivery

21 Fats Provide Efficient Fuel Storage

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23 Waxes Waxes are esters of long chain saturated and unsaturated fatty acids with long chain alcohols Insoluble and have high melting points Variety of functions: Storage of metabolic fuel in plankton Protection and pliability for hair and skin in vertebrates Waterproofing of feathers in birds Protection from evaporation in tropical plants and ivy Used by people in lotions, ointments, and polishes

24 Structural Lipids in Membranes (Polar) Contain polar head groups and nonpolar tails (usually attached fatty acids) Diversification can come from: modifying a different backbone changing the fatty acids modifying the head groups The properties of head groups determine the surface properties of membranes Different organisms have different membrane lipid head group compositions Different tissues have different membrane lipid head group compositions

25 Structural lipids in membranes 1. Glycerophospholipid 1) 구조 glycerol 에결합되어있는 2 개의지방산이소수성부위를형성 1 머리부분의극성종류에따라명명 O 2 CH 2 -O-C- : C 16 /C 18 인포화지방산 O CH 2 -O-C- : C 18 /C 20 인불포화지방산 O CH 2 -O-P-O- O 2) Ether Lipid 염증, allergy 관련 1 plasmalogen ether 결합된한개의 alkenyl chain : 심장인산지방질의 1/2 2 platelet-activating factor(paf) glycerol 의 1 C 위치에 ether 결합된긴 alkyl chain : 호염기구 basophil 에서분비되어 2 C 위치에 carboxyl 기가 ester 결합 혈소판의응집 & 혈소판으로부터 serotonin 의분비를촉진시키는강력한물질

26 2. Sphingolipid 1) 구조 1 Sphingosine이나그유도체 1분자 + 사슬지방산 1분자 + glycoside 결합 / phosphodiester 결합 2 glycerophospholipid와다른점 : glycerol 포함ⅹ 3 OH-CHCH=CH-(CH 2 ) 12 -CH 3 O CH-NH-C : ( 지방산 ) ceramide CH 2 -O-X 2) 종류 1 ceramide (H=X): 모든 sphingolipid의기본구조 2 sphingomyelin (X=phosphocholine): sphingolipid cell membrane, myelin sheath 3 Glucosylcerebroside 4 globoside 5 ganglioside * N-acetylneuraminic acid (sialic acid) 3) 역할 : 신경세포의원형질막, 세포표면에서 recognition site로작용

27 Some common types of storage and membrane lipids

28 Glycerophospholipids Primary constituents of cell membranes Two fatty acids form ester linkages with the first and second hydroxyl groups of L glycerol 3 phosphate Head group is charged at physiological ph

29 General Structure of Glycerophospholipids Unsaturated fatty acids are commonly found connected to C2 The highly polar phosphate group may be further esterified by an alcohol; such substituent groups are called the head groups

30 Examples of Glycerophospholipids Mt 에多