厦大生化Chapter 26课件.pptVIP

Chapter 26 The biosynthesis of membrane lipids and steroids 26.1 Phosphatidate is a common intermediate in the synthesis of phospholipids and triacylglycerols 26.1.1 The synthesis of phospholipids requires an activated intermediate Phospholipid synthesis = the combination of a diacylglyceride with an alcohol Anabolic reaction Diacylglycerol or alcohol should be activated. Synthesis from an activated diacylglerol Synthesis form an activated alcohol 26.1.2 Plasmalogens and other ether phospholipids are synthesized from dihydroxyacetone phosphate 26.1.3 Sphingolipids are synthesized from ceramide 26.1.4 Respiratory distress syndrome and Tay-Sachs disease result from the disruption of lipid metabolism 26.2 Cholesterol is synthesized from acetyl coenzyme A in three stages 26.2.1 The synthesis of mevalonate, which is activated as isopentenyl pyrophosphate, initiates the synthesis of cholesterol 26.2.2 Squalene cyclizes to form cholesterol 26.3 The complex regulation of cholesterol biosynthesis takes place at several levels 3-hydroxy-3-methylglutaryl CoA reductae The synthesis of reductase mRNA is controlled by sterol regulatory element binding protein. The translation of reductase mRNA. The degradation of the reductase. Phosphorylation decrease the activity of the redutase. 26.3.1 Lipoproteins transport cholesterol and triacylglycerols throughout the organism 26.4 Important derivatives of cholesterol include bile salts and steroid hormones. 26.4.1 Pregnenolone, a precursor for many other steroids, is formed from cholesterol by cleavage of its side chain 26.4.2The synthesis of progesterone and corticosteroids from pregnenolone 26.4.5 The synthesis of androgens and estrogens from pregnenolone 26.4.6 Vitamin D is derived from cholesterol by the ring-splitting activity of light Key terms Phosphatidate Triacylglycerol Phospholipid Sphingolipid Cholesterol Lipoprotein particle Low-density