脂肪酸的代謝ppt課件(已改無(wú)錯(cuò)字)
2023-02-04 20:50:35 本頁(yè)面
【正文】 rm (c). When a rhodopsin molecule is excited by visible light, the 11cisretinal undergoes a series of photochemical reactions that convert it to alltransretinal (e), forcing a change in the shape of the entire rhodopsin molecule. This transformation in the rod cell of the vertebrate retina sends an electrical signal to the brain that is the basis of visual transduction. (a) βCarotene is the precursor of vitamin A1. Isoprene structural units are set off by dashed red lines. Cleavage of carotene yields two molecules of vitamin A1 (retinol) (b). Vitamin A1 and its precursor and derivatives 由鯊烯轉(zhuǎn)化為膽固醇 豆甾醇 麥角甾醇 膽固醇的合成是一個(gè)高度耗能的過(guò)程，合成一個(gè)膽固醇需 18個(gè)乙酰輔酶 A，36個(gè) ATP， 16個(gè) NADPH。能源物質(zhì)過(guò)剩時(shí)，膽固醇的合成速度加快，午夜時(shí)，合成速度較快，膳食固醇類(lèi)，特別是植物固醇可抑制膽固醇的合成。 Lipoproteins. (a) Structure of a lowdensity lipoprotein (LDL). Apolipoprotein B100 (apoB100) is one of the largest single polypeptide chains known, with 4,636 amino acid residues (Mr 513,000). (b) Four classes of lipoproteins, visualized in the electron microscope after negative staining. Clockwise from top left: chylomicrons, 50 to 200 nm in diameter。 VLDL, 28 to 70 nm。 HDL, 8 to 11 nm。 and LDL, 20 to 25 nm. 脂類(lèi)是由脂蛋白運(yùn)輸?shù)? Lipoproteins and lipid transport. (a) Lipids are transported in the bloodstream as lipoproteins, which exist as several variants that have different functions, different protein and lipid positions, and thus different densities. Dietary lipids are packaged into chylomicrons。 much of their triacylglycerol content is released by lipoprotein lipase to adipose and muscle tissues during transport through capillaries. Chylomicron remnants (containing largely protein and cholesterol) are taken up by the liver. Endogenous lipids and cholesterol from the liver are delivered to adipose and muscle tissue by VLDL. Extraction of lipid from VLDL (along with loss of some apolipoproteins) gradually converts some o
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