脂肪酸的代谢.ppt

鞘磷脂2动物细胞中糖基神经酰胺，神经节苷脂和鞘磷脂的由神经酰胺合成。15.花生四烯酸是合成前列腺素，血拴烷和白三烯的前体。前列腺素内过氧化物合成酶催化PGH2的合成阿斯匹林使环加氧酶失活胆固醇的合成甲羟戊酸的合成甲羟戊酸合成的机制HMG-CoA还原酶的活力受合成速度、降解速度及磷酸化和脱磷酸调控。甲羟戊酸到鲨烯的转化OxidationatC-15convertsretinoltothealdehyde,retinal(c),andfurtheroxidationproducesretinoicacid(d),ahormonethatregulatesgeneexpression.Retinalcombineswiththeproteinopsintoformrhodopsin(notshown),avisualpigmentwidespreadinnature.Inthedark,retinalofrhodopsinisinthe11-cisform(c).Whenarhodopsinmoleculeisexcitedbyvisiblelight,the11-cis-retinalundergoesaseriesofphotochemicalreactionsthatconvertittoall-trans-retinal(e),forcingachangeintheshapeoftheentirerhodopsinmolecule.Thistransformationintherodcellofthevertebrateretinasendsanelectricalsignaltothebrainthatisthebasisofvisualtransduction.(a)β-CaroteneistheprecursorofvitaminA1.Isoprenestructuralunitsaresetoffbydashedredlines.Cleavageof-caroteneyieldstwomoleculesofvitaminA1(retinol)(b).VitaminA1anditsprecursorandderivatives麦角甾醇豆甾醇由鲨烯转化为胆固醇胆固醇的合成是一个高度耗能的过程，合成一个胆固醇需18个乙酰辅酶A，36个ATP，16个NADPH。能源物质过剩时，胆固醇的合成速度加快，午夜时，合成速度较快，膳食固醇类，特别是植物固醇可抑制胆固醇的合成。Lipoproteins.(a)Structureofalow-densitylipoprotein(LDL).ApolipoproteinB-100(apoB-100)isoneofthelargestsinglepolypeptidechainsknown,with4,636aminoacidresidues(Mr513,000).(b)Fourclassesoflipoproteins,visualizedintheelectronmicroscopeafternegativestaining.Clockwisefromtopleft:chylomicrons,50to200nmindiameter;VLDL,28to70nm;HDL,8to11nm;andLDL,20to25nm.脂类是由脂蛋白运输的*********二、其他脂类的生物合成Biosynthesisofphosphatidicacid.Afattyacylgroupisactivatedbyformationofthefattyacyl–CoA,thentransferredtoesterlinkagewithL-glycerol3-phosphate,formedineitherofthetwowaysshown.PhosphatidicacidisshownherewiththecorrectstereochemistryatC-2oftheglycerolmolecule.Toconservespaceinsu