英文脂和生物膜PPT課件

1、Lipids and Membranes第1頁/共27頁Lipids a heterogeneous class of naturally occurring organic compounds classified together on the basis of common solubility properties insoluble in water, but soluble in aprotic organic solvents including diethyl ether, chloroform, methylene chloride, and acetone Lipids i

2、nclude fatty acids, triacylglycerols, sphingolipids, phosphoacylglycerols, glycolipids, lipid-soluble vitamins prostaglandins, leukotrienes, and thromboxanes cholesterol, steroid hormones, and bile acids第2頁/共27頁Fatty Acids an unbranched-chain carboxylic acid, most commonly of 12 - 20 carbons, derive

3、d from hydrolysis of animal fats, vegetable oils, or phosphodiacylglycerols of biological membranes In the shorthand notation for fatty acids the number of carbons and the number of double bonds in the chain are shown by two numbers, separated by a colon第3頁/共27頁Fatty Acids20:420:418:318:318:218:218:

4、118:116:116:120:020:018:018:016:016:014:014:012:012:0Carbon Atoms/Carbon Atoms/Double BondsDouble Bondsmpmp(C)(C)Common Common NameName-49-49-11-11-5-51616-0.5-0.577777171636358584444arachidonic acidarachidonic acidlinolenic acidlinolenic acidlinoleic acidlinoleic acidoleic acidoleic acidpalmitoleic

5、 acidpalmitoleic acidarachidic acidarachidic acidstearic acidstearic acidpalmitic acidpalmitic acidmyristic acidmyristic acidlauric acidlauric acidSaturatedSaturatedUnsaturatedUnsaturated第4頁/共27頁Fatty Acids Among the fatty acids most abundant in plants and animals nearly all have an even number of c

6、arbon atoms, most between 12 and 20, in an unbranched chain the three most abundant are palmitic (16:0), stearic (18:0), and oleic (18:1) acids in most unsaturated fatty acids, the cis isomer predominates; the trans isomer is rare unsaturated fatty acids have lower melting points than their saturate

7、d counterparts; the greater the degree of unsaturation, the lower the melting point第5頁/共27頁Triacylglycerols an ester of glycerol with three fatty acids natural soaps are prepared by boiling triglycerides (animal fats or vegetable oils) with NaOH, in a reaction called saponification (Latin, sapo, soa

8、p)A triacylglycerolA triacylglycerol(a triglyceride)(a triglyceride)C C H H2 2O O - -C C R RO OO OO OC C H H2 2O O - -C C R R N N a aO O H H , , H H2 2O OC C H H2 2O O H HC C H H2 2O O H H 1,2,3-Propanetriol 1,2,3-Propanetriol(Glycerol, glycerin)(Glycerol, glycerin)+ +R RC C O O O O- -N N a a+ +Sodi

9、umSodiumSoapsSoapsH H O O C C H HR R C C O O - -C C H HR R C C O O O O- -N N a a+ +R R C CO O O O- -N N a a+ +第6頁/共27頁Soaps Soaps form water-insoluble salts when used in water containing Ca(II), Mg(II), and Fe(III) ions ()+ + +A sodium soapA sodium soap(soluble in water as micelles)(soluble in water

10、 as micelles)Calcium salt of a fatty acidCalcium salt of a fatty acid(insoluble in water)(insoluble in water)2 2 C C H H3 3( (C C H H2 2) )1 1 4 4C C O O O O- -N N a a+ +C C a a2 2 + + C C H H3 3( (C C H H2 2) )1 1 4 4C C O O O O- - 2 2C Ca a2 2 + +2 2 N N a a+ +第7頁/共27頁P(yáng)hosphoacylglycerols (phospho

11、glycerides) are the second most abundant group of naturally occurring lipids found almost exclusively in plant and animal membranes, which typically consist of 40% -50% phosphoacylglycerols and 50% - 60% proteins the most abundant phosphoacylglycerols are derived from phosphatidic acid, a molecule i

12、n which glycerol is esterified with two molecules of fatty acid and one of phosphoric acid the three most abundant fatty acids in phosphatidic acids are palmitic (16:0), stearic (18:0), and oleic (18:1)第8頁/共27頁P(yáng)hosphoacylglycerols A phosphatidic acid further esterification with a low-molecular-weigh

13、t alcohol gives a phosphoacylglycerol the most common of these low-molecular-weight alcohols areC C H H2 2C C H HC C H H2 2- -O O - -P P- -O O- -O OO OO OO Oglycerolglycerolpalmitic acidpalmitic acidstearic acidstearic acidO OO O- -第9頁/共27頁P(yáng)hosphoacylglycerolsName and FormulaName and FormulaName of

14、PhospholipidName of Phospholipidethanolamineethanolamine+ +cholinecholinephosphatidylcholinephosphatidylcholine(lecithin)(lecithin)phosphatidylethanolaminephosphatidylethanolamine(cephalin)(cephalin)serineserinephosphatidylserinephosphatidylserineN N H H3 3+ +H H O O C C H H2 2C C H H C CO O O O- -H

15、 H O O C C H H2 2C C H H2 2N N ( (C C H H3 3) )3 3H H O O C C H H2 2C C H H2 2N N H H2 2第10頁/共27頁P(yáng)hosphoacylglycerolsinositolinositolphosphatidylinositolphosphatidylinositolH H O OH H O OO O H HO O H HO O H HO O H HH H O O C C H H2 2C C H H C CH H2 2O O H Hglycerolglycerolp phosphatidylglycerolhosph

16、atidylglycerolO O H HphosphatidylglycerolphosphatidylglycerolH H O O C C H H2 2C C H H C CH H2 2O O P PO O C C H H2 2C C H H O O C C R R3 3O O H HO O- -O OC C H H2 2O O C C R R4 4O OO Odiphosphatidylglyceroldiphosphatidylglycerol(cardiolipin)(cardiolipin)第11頁/共27頁P(yáng)hosphoacylglycerols A lecithinC C H

17、 H2 2C C H HC C H H2 2O OO OO OO OO OP P O O C C H H2 2C C H H2 2N N ( (C CH H3 3) )3 3O OO O- -+ +palmitic acidpalmitic acidstearic acidstearic acidglycerolglycerolcholinecholine第12頁/共27頁Waxes An ester of a long-chain fatty acid and alcohol from the Old English word weax = honeycombC C H H3 3( (C C

18、 H H2 2) )1 14 4C C O O ( (C C H H2 2) )2 29 9C C H H3 3O OA major component of beeswaxA major component of beeswax(honeycombs)(honeycombs)C C H H3 3( (C C H H2 2) )3 30 0C C O O ( (C C H H2 2) )3 33 3C C H H3 3O OA major component of A major component of carnauba waxcarnauba wax(the Brazilian wax p

19、alm)(the Brazilian wax palm)C C H H3 3( (C C H H2 2) )1 14 4C C O O ( (C C H H2 2) )1 15 5C C H H3 3O OA major component ofA major component ofspermacetti waxspermacetti wax(head of the sperm whale)(head of the sperm whale)第13頁/共27頁Sphingolipids contain sphingosine, a long-chain aminoalcohol from wh

20、ich this class is namedO O H H( (C C H H2 2) )1 12 2C C H H3 3H H O ON N H H2 2SphingosineSphingosineO O H H( (C C H H2 2) )1 12 2C C H H3 3H H O ON N H H C C R RA ceramideA ceramide(an N-acylsphingosine)(an N-acylsphingosine)O O P PO O C CH H2 2C CH H2 2N N ( (C C H H3 3) )3 3( (C C H H2 2) )1 12 2

21、C C H H3 3H H O ON N H H C C R RA sphingomyelinA sphingomyelinO OO O- -+ +O OO O第14頁/共27頁Glycolipids a compound in which a carbohydrate is bound to an -OH of the lipid many glycolipids are derived from ceramidesO O( (C C H H2 2) )1 12 2C C H H3 3H H O ON N H H C C R RO OH HH H O OH HH H O OH HH HO O

22、 H HH HO O H Ha a-glycosidic bond-glycosidic bonda unit of a unit of -D-glucopyranose-D-glucopyranoseO O第15頁/共27頁Steroids a group of plant and animal lipids that have this tetracyclic ring structureA AB BC CD D第16頁/共27頁SteroidsH HC CH H3 3H HH HC CH H3 3H H The features common to the ring system of

23、most naturally occurring steroids are illustrated here 第17頁/共27頁Androgens male sex hormones synthesized in the testes responsible for the development of male secondary sex characteristicsA An nd dr ro os st te er ro on ne eT Te es st to os st te er ro on ne eO OH HO OH HH HH H3 3C CH HH HH H3 3C CH

24、H3 3C CH HH HH H3 3C CH HO OH HO O第18頁/共27頁Estrogens female sex hormones synthesized in the ovaries responsible for the development of female secondary sex characteristics and control of the menstrual cycleP Pr ro og ge es st te er ro on ne eE Es st tr ra ad di io ol lH H3 3C CH HH HH H3 3C CH HC C

25、= = O OH HO OC C H H3 3O O H HH H O OH HH HH HH H3 3C C第19頁/共27頁CholesterolH H3 3C CH HO OH H3 3C CH HH HH H The steroid of most interest in our discussion of biological membranes is cholesterol 第20頁/共27頁Biological Membranes In aqueous solution, phosphoglycerides spontaneously form into a lipid bila

26、yer, with a back-to-back arrangement of lipid monolayers (see Figure 7.10) polar head groups are in contact with the aqueous environment nonpolar tails are buried within the bilayer the major force driving the formation of lipid bilayers is hydrophobic interaction the arrangement of hydrocarbon tail

27、s in the interior can be rigid (if rich in saturated fatty acids) or fluid (if rich in unsaturated fatty acids)第21頁/共27頁Biological MembranesFigure 7.10 A lipid bilayer 第22頁/共27頁Biological Membranes the presence of cholesterol increases rigidity with heat, membranes become more disordered; the transi

28、tion temperature is higher for more rigid membranes; it is lower for less rigid membranes plant membranes have a higher percentage of unsaturated fatty acids than animal membranes the presence of cholesterol is characteristic of animal rather than plant membranes animal membranes are less fluid (mor

29、e rigid) than plant membranes the membranes of prokaryotes, which contain no appreciable amounts of steroids, are the most fluid第23頁/共27頁Membrane Proteins: transport substances across membranes; act as receptor sites, and sites of enzyme catalysis Peripheral proteins bound by electrostatic interactions can be removed by raising the ionic strength Integral proteins bound tightly