Lehninger Principles of Biochemistry Fourth Edition

Transcription

1 David L. Nelson and Michael M. Cox Lehninger Principles of Biochemistry Fourth Edition Chapter 10: Lipids Copyright 2004 by W. H. Freeman & Company

2 Biological Importance 1. Fats & oils storage lipids 2. Phospholipids & sterols structural lipids 3. Others i. Cofactors ii. Electron carriers iii. Light-absorbing pigments iv. Hydrophobic anchors for proteins v. chaperone to help membrane protein fold vi. Emulifying agents in digestive tract vii. Hormones viii. Intracellular messenger

3 triacylglycerols 1. STORAGE LIPIDS Fats & Oils derivatives of fatty acids (FA) FA hydrocarbon derviatives like fossil fuel Burn them exergonic reaction Two example: triacylglycerols and waxes

4 triacylglycerols Fatty Acids FA=Carboxylic acid + hydrocarbon chain(hc) HC between 4-36 carbon long (C 4 to C 36 ) Saturated HC no double bond Unsaturated HC one or >one A few has OH, methyl-group branch, rings

5 triacylglycerols Nomenclature of FA Palmitic Acid wth 16C, saturated: 16:0 Oleic Acid wth 18C, one double: 18:1 To show the position of double bonds (delta) used: How? no of Catom Example: # of C=20; # of DB=2, where? between C-9&C-10 C-12&C-13 SO 20:2 ( 9,12)

6 triacylglycerols

7 triacylglycerols Common most monounsaturated FA 9 Most polyunsaturated FA 9,12 or 9,15

8 triacylglycerols cis-configuration highly common Trans-configuration: produced by microp of rumen of ruminants And during the hydrogenation of fish and vegetable oils Trans FA LDL (bad cholesterol)

9 triacylglycerols Physical properties Depending on # of Carbon & # of double b. The more hydrocarbon the more hydrophobic The fewer double bond the more hydrophobic The more hydrocarbon the more melting point The higher double bond the lower melting point

10 triacylglycerols

11 triacylglycerols

12 triacylglycerols

13 triacylglycerols Melting No double bond Atoms close each other Possibility of van der Waals Size Carboxyl side is polar; polar/hydrocarbon Double bond number Not enough, cis configuration (kink)

14 Triacylglycerols triacylglycerols

15 triacylglycerols Types of triacylglycerols Simple triacylglycerols: only one kind of fatty acids (example: 16:0 tristearin) Mixed triacylglycerol (mostly): 2 or more different fatty acids. Triacylglycerols nonpolar Lipids lower speicifc gravity than water 2 layers oil water

16 triacylglycerols Roles of Triacylglycerols Store energy Insulation Stored in cell as oily droplets serving as depots of metabolic fuel adipocytes for vertebrates fat droplets As oil in seeds of plants Lipases: enzyme to hydrolyse TA to fatty acids to be transported anywhere as an energy battery

17 triacylglycerols

18 triacylglycerols

19 triacylglycerols Why body uses TA to store energy More reduced than sugar twice energy when hydrolysed Hydrophobic unhydrated less space but higher energy (2 g water/1 g polysaccharide to hydrate it) 15 kg TA months Full glycogen depots supply less than one day s energy

20 triacylglycerols TA for insulation TA under skin low temperature Seals, walruses, penguins etc (warm-blooded polar animals) full of TA Hibernating animals (bear) both energy and insulation

21 triacylglycerols

22 Simple and mixed TA in food. So different FA in size and saturation degree triacylglycerols

23 Waxes Waxes

24 Waxes

25 Waxes Function of waxes depends on Waxes are water repellent Firm consistency Waxes for hair pliable (easy to bend), lubricated, waterproof Birds feather Tropical plants leaves for water loss Industeial usage Ointments, lotions and polishes from waxes

26 Structural lipids in Membrane A barrier A double layer of lipids Amphipatic (charged and hydrophobic)

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28 I II III IV V Called Phospholipid Why? Polar group to hydrophobic moeity by Phosphodiester bond Called glycolipid Why Sugar at polar head

29 1. Glycerophospholipid Glycerophospholipid

30 Glycerophospholipid

31 Glycerophospholipid

32 Glycerophospholipid Fatty Acids Glycerophospholipid Fatty Acids Differences in different organism, tissues, even cells Generally C-1 to C 16 or C 18 C-2 to C 18 or C 20

33 Phospholipids with ether linked fatty acids: Ether lipids Ester Vertebrate heart tissue (plasmalogen %50 of phospholipids) Halophilic (salt lovers) bacteria Cilliated protists Certain invertebrates

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35 Galactolipids : plants (most abundant) Localized in thylokoid membrane in chloroplast Make up 70-80% of total membrane lipid No phosphate intake -1 Plants also have sulfolipids (sulfonated glucose to a diacylglycerol in glycosidic linkage)

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37 Archeabacteria s membrane lipids (Hydrocarbon) Glycerol dialkyl glycerol tetraethers (GDGTs)

38 Sphingolipids 4th biggest group Polar head + 2 nonpolat tail No glycerol Majority no phosphate group Extra sphingosine Its strucutre: 1 sphingosine + 1 FA + head

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40 Three subclass of sphingolipids 1. Sphingomyelins 2. Glycosphingolipids 3. Gangliosides

41 Three subclass of sphingolipids 1. Sphingomyelins Phosphocholine (polar head group X) So called glycerophospholipid (due to phosphate group) Animal cells Prominent in myelin sheat around axons 2. Glycosphingolipids 3. Gangliosides

42 Three subclass of sphingolipids 1. Sphingomyelins 2. Glycosphingolipids Generally outer face of plasma membrane Sugar (1 or 2) to ceramidine wthout phosphate g. Cerebroside: single sugar Glucose nonneural tissue Galactose neural tissue Globosides: neutral 2 or more sugar D-glucose; D-galactose; N-acetyl-D-galactosamine 3. Gangliosides

43 Three subclass of sphingolipids 1. Sphingomyelins 2. Glycosphingolipids 3. Gangliosides most complex one Oligosaccharide + N-acetylneuraminic acid (sialic acid) Negative charge due to sialic a. Accumulated in outer surface of plasma membrane Kinds and amount change during development

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46 Degraded in lysosomes

47 Sterols With steroid nucleus ( 4 fused rings; 3X6+1X5) Planar Rigid No rotation Most eukaryotics membrane Plant can synthesize Animals can do But bacteria can not (a few exception) Funciton: some in signaling, in the structure of bile acids (cholestrol)

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49 Lipids with active role 1. Potent signals (hormones) passive role 2. Enzyme cofactor (in cellular respiration and photosynthesis and in transfer of sugar moeties) Vitamines A, D, E,K 3. Pigment molecules (to absorb light to see (eye) or to produce chemical energy (leaf), colorization (orange of carrot) 4. volatile lipids (communication of plants)

50 Phosphatidylinositol: Regulate metabolism Phosphatidylinositol and its phosphorylated derivatives: phosphatidylinositol 4,5- bisphosphate inositol 1,4,5-trisphosphate (IP3) some regulatory proteins binds to phosphatidylinositol 3,4,5-bisphosphate source of intracellular messengers.

51 Eicosanoids Paracrine hormone (near point) involved in Reproduction inflammation Pain Fever Formation of blot clots Regulation of blood pressure Gastric acid segration Etc

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54 Prostaglandins: prostate gland Two known groups PGE ether-soluble (subgroups PGE 1...) PGF water soluble Regulation of camp Regulation of celular and tissue functions

55 Thromboxanes By thrombocytes In blood clotting

56 Leukotrienes in leukocytes Powerful signals leukotriene D4, contraction of the muscle lining the airways to the lung. Overproduction asthmatic attacks strong contraction of smooth m. of lung (anaphylactic shock) potentially fatal allergic reaction in individuals hypersensitive to bee stings, penicillin, or other agents

57 Steroid hormones derivatives of sterols lack alkyl chain attached to D ring of cholesterol SH produced blood stream enter cell binds to protein protein expression [low] enough because of its affinity major Steroid hormones: sex hormones, hormones from adrenal cortex: cortisol, aldosterone

58 male sex hormone organ: testis female sex h ovary and placenta regulation glucose metabolism of regulation of salt extraction both from adreanl cortex synthetic drug for inflammation potent growth regulator in vascular plants

59 Volatile Signals lipophilic compound for plant to.. attrack pollinators and helpful organisms against enemies repel herbivors communicate with friends exmple: josmante

60 Vitamins vitamins essential (mostly not produced by animals, most in diet) grouped into two soluble in polar s. (water-soluble vitamins) soluble in nonpolar solvent(fat-soluble v) A,D,E,K: isoprenoid compounds by condansation of poly-isoprene units

61 Vitamin D 3 cholecalciferol from skin from 7-dehydrocholesterol ultiately converted to 1,25-d,hydroxyvitamin D 3 hormone which regulates.. calcium uptake by intestine calcium level in kidney and bones interact directly with its target protein in nucleus deficincy defective bone formation and rickets vitamin D 2 by yeast and similar effect like D 3 added into milk

62 retinol Vitamin A various forms functioning as.. hormone such as retinoic acid receptor of cell nucleus to regulate gene in epithelial cell development visual pigment as retinal initiate response of rop and cone to light sources: fish oil, liver,egg,milk, butter beta-carotene: pigments that gives carrots, sweet potatoes, yellow veetables Syptoms:dryness in skin,eyes and mocous, night blidness

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64 Tocopherols Aromatic ring + along isoprenoid side chain Hydrophobic so associate with Cell membrane Lipid droplets Lipoproteins Antioxidant because of its aromatic ring Sources: egg, vegetable oil, white germ Deficiency rare; symp: RBC fragility

65 A cycle of oxidation & reduction during the formation of active protrombin active protrombin: an enzyme converting fibrinogen to fibrin fibrin: insoluble protein holding bloot clot together Deficiency rare; only in new borns Source: green plants, K 2 intestinal bacteria

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71 Working with Lipids First degradation Alkali Acidic Hydrolytic enzymes Glycosidase phospholipase

72 Working with Lipids Extraction Neutral lidips (TG, waxes)by the solvents Ethyl ether, chloroform, benzen (hydrophobic) Membrane Lidips by more polar solvents Ethanol, methanol Example: chloroform, ethanol, water (1:2:0.8) Then add water» Two layers:lipids in chloroform

73 Seperation by.. Adsorption chromotography Silica gel: polar but insoluble Polar lipids adsorb to silica gel Neutral Lipids eluted To remove polar lipids polar solvents: For polar, uncharged:acetone Charged: methanol TLC: Very similar to Ad. Ch. Plate with silica Neutral lipids run faster Trick in staining lipids Spray(a dye: RHODAMINE) Đodine fumes: yellow-brown Đnteract with double bond Other commercials

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