Figure, 21-23Head group attachment

1. Backbone Glycerol, sphingosine2. Fatty acid3. Hydrophilic head4. Exchange head group

Membrane phospholipids:Glycerophospholipidssphingolipids

Figure, 21-24Two strategies for forming phosphodiester bond

Signal transduction

Figure, 21-26Polar head in eukaryotes

Figure, 21-27, 28-aSalvage pathway in yeast

S-adenosylmethionineS-adenosylhomocysteine

Major pathway in Eukaryotes(yeast)

phosphatidylserine

In mammals(no CDP-diacylglycerol and serineto PS)Head-group exchange(PC—PS or PE—PS)

Figure, 21-28 bPhosphatidylcholine in mammals

Salvage pathwayCholine reused (strategy 2)

Mutation in ethanolamine kinaseEliminate phosphatidylethanolamine Synthesis: less in membraneTransient paralysis: electrical stimulation

Figure, 21-29 summary of the pathways for synthesis of major phospholipid

Figure, 21-30Ether lipid, Plasmalogen

platelet-activating factorHalf 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

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

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. secretary 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?