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Figure, 21-23Head group attachment
1. Backbone Glycerol, sphingosine (serine)2. Fatty acid ( Phosphatidic acid,
DAG)3. Hydrophilic head4. Exchange head group
Membrane phospholipids:Glycerophospholipidssphingolipids
Smooth ERMitochondria inner membrane
Figure, 21-24Two strategies for forming phosphodiester bond
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FIGURE 21–25 Origin of the polar head groups of phospholipids in E. coli.
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Kinase--Signal transduction
Figure, 21-26Polar head in eukaryotes
Mitochondria inner membraneHelp enzymes for energy metabolism--complex IV and V, apoptosis (cytochrome C release)
Figure, 21-27 Yeast (Eukaryotic cells –major source of PE and PC)
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PS
PE
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Figure, 21-27
S-adenosylmethionine (SAM)
S-adenosylhomocysteine
PC
Fig. 21-28 a head group exchange (only in mammals—ER)
Figure, 21-28 bPhosphatidylcholine in mammalsPE (the same strategy)
Salvage pathwayCholine reused (strategy 2)
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Figure, 21-29 summary of the pathways for synthesis of major phospholipid
Mutation in ethanolamine kinase(easily shocked)Eliminate phosphatidylethanolamine Synthesis: less in membraneTransient paralysis: electrical stimulation
In mammals(no CDP-diacylglycerol and serineto PS)
In liver only
Figure, 21-30Ether lipid, Plasmalogenplatelet-activating factor
Half of the heart phospholipid
Head group
peroxisome
Figure, 21-31Sphingolipids
2nd big groupLung surfactant
Step 1
18 C amine
O-
Step 2
Step 3
Step 4
(SER)
GlycolipidGlycosidic linkage
Golgi
Figure, 21-32Not required in diet
Cell membraneSteroid hormone Bile acids
Figure, 21-33Cholesterol biosynthesisIn liver
6C
5C
30C
condensation
polymerization
cyclization
Figure, 21-34Synthesis of mevalonate
cytosol
Rate-limiting step Release 3CoA(membrane of the SER)
Figure, 21-35Mevalonate to activated isoprene
Use 3 ATPRelease 1 CO2
Figure, 21-36Squalene
10C
15C
30C
(rose oil)
Figure, 21-37Ring closure
20 stepsMethyl group migration and removal
Mixed function oxidase
plants
Figure, 21-38Cholesteryl esters
Stored or in lipoprotein particles
Figure 21-39Plasma Lipoproteins-Lipid transport(LDL)
Figure 21-39B
TABLE 21-1
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TABLE 21-2
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Figure21-40Lipoprotein andLipid transport
apoE
apoCII--lipase
apoB100
apoB100
apoA-I
Figure 21-42Uptake of cholesterol by receptor-mediatedendocytosis
Figure21-40Lipoprotein andLipid transport
apoA-I
SR-BIABC1
Figure 21-41
Surface of nascent HDL
Chylomicron and VLDL remnants
Figure, 21-44Regulation of cholesterol
dp
p
Inhibit transcription
Figure, 21-43SREBP (sterol regulatory element-binding protein) activationSCAP: SREBP cleavage-activating protein—binds to cholesterol and other sterols
HMG CoA reductaseLDLR
Figure, 21-45Inhibitors of HMG-CoA reductaseCholestyramine-resin binds to bile acids-prevent reabsorption
Competitive inhibition of HMG-CoA reductase
statin
Figure, 21-48 isoprenoidPrenylationProetins are anchored to cellular membrane
Figure, 21-46Steroid hormones from cholesterol
Increase gluconeogenesisAnd TAG cycle
Figure, 21-47Side chain cleavage
Adrenal cortexmitochondria
Hydroxylation and cleavage
Fatty liver:
TAG formation and export imbalanceExtensive accumulation of TAG—cirrhosis1. Free fatty acids increase in plasma, then to liver accumulation2. Block production of plasma lipoproteins a. apolipoprotein synthesis b. lipoprotein c. phospholipid d. secretory pathway
Ethanol—fatty liverEthanol is converted to be acetaldehyde by alcohol dehydrogenase and NADH is producedExcess NADH inhibit CAC and increase lipogenesis (cholesterol)
Homework: How insulin regulates lipid metabolism?