脂肪酸的代謝ppt課件-資料下載頁(yè)
2025-01-04 20:50本頁(yè)面
【正文】 f it to LDL, which delivers cholesterol to extrahepatic tissues or returns to the liver. The liver takes up LDL, VLDL remnants, and chylomicron remnants by receptormediated endocytosis. Excess cholesterol in extrahepatic tissues is transported back to the liver as HDL. In the liver, some cholesterol is converted to bile salts. (b) Blood plasma samples collected after a fast (left) and after a highfat meal (right). Chylomicrons produced after a fatty meal give the plasma a milky appearance. Reaction catalyzed by lecithincholesterol acyl transferase (LCAT). This enzyme is present on the surface of HDL and is stimulated by the HDL ponent apoAI. Cholesteryl esters accumulate within nascent HDLs, converting them to mature HDLs. 載脂蛋白在肝細(xì)胞內(nèi)質(zhì)網(wǎng)合成，在內(nèi)質(zhì)網(wǎng)組裝成脂蛋白顆粒，在高爾基體加工，包裝成分泌小泡，分泌到肝細(xì)胞外。 脂蛋白顆粒的胞吞和降解 LDL受體的結(jié)構(gòu) SREBP activation. Sterol regulatory elementbinding proteins (SREBPs, shown in green) are embedded in the ER when first synthesized, in a plex with the protein SREBP cleavageactivating protein (SCAP, red). (N and C represent the amino and carboxyl termini of the proteins.) When bound to SCAP, SREBPs are inactive. When sterol levels decline, the plex migrates to the Golgi plex, and SREBP is cleaved by two different proteases in succession. The liberated aminoterminal domain of SREBP migrates to the nucleus, where it activates transcription of sterolregulated genes. Regulation of cholesterol formation balances synthesis with dietary uptake. Glucagon promotes phosphorylation (inactivation) of HMGCoA reductase。 insulin promotes dephosphorylation (activation). X represents unidentified metabolites of cholesterol that stimulate proteolysis of HMGCoA reductase. 動(dòng)脈斑的照片 膽酸和膽酸鹽的合成 降低血清膽固醇的藥物 7α脫氫酶的混合氧化酶活性 固醇類激素的合成 孕酮 孕烷醇酮 睪酮 醛固酮 雌二醇 一種興奮劑 基本要求 。 （重點(diǎn)） 。 、鞘脂類和甾醇的合成途徑及調(diào)控。
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