Chylomicron - wikipedia Chylomicron This article needs additional citations for verification. Please help improve this article by adding citations to reliable sources. Unsourced material may be challenged and removed. ( December 2009 ) Schematic image showing a chylomicron Chylomicrons ( from the Greek chylo, meaning milky fluid, and micron, meaning small particle ) are lipoprotein particles that consist of triglycerides ( 85 -- 92 % ), phospholipids ( 6 -- 12 % ), cholesterol ( 1 -- 3 % ), and proteins ( 1 -- 2 % ). They transport dietary lipids from the intestines to other locations in the body. Chylomicrons are one of the five major groups of lipoproteins : chylomicrons ( a.k.a. ULDL ultra low - density lipoprotein relative to surrounding water ), very low - density lipoprotein, intermediate - density lipoprotein, low - density lipoprotein, high - density lipoprotein, that enable fats and cholesterol to move within the water - based solution of the bloodstream. Contents 1 Function 2 Origin 3 Stages 3.1 Nascent chylomicrons 3.2 Mature chylomicron 3.3 Chylomicron remnant 4 References Function Chylomicron structure ApoA, ApoB, ApoC, ApoE ( apolipoproteins ) ; T ( triacylglycerol ) ; C ( cholesterol ) ; green ( phospholipids ) Chylomicrons transport lipids absorbed from the intestine to adipose, cardiac, and skeletal muscle tissue, where their triglyceride components are hydrolyzed by the activity of the lipoprotein lipase, allowing the released free fatty acids to be absorbed by the tissues. When a large portion of the triacylglycerol core have been hydrolyzed, chylomicron remnants are formed and are taken up by the liver, hereby transferring dietary fat also to the liver. Origin Chylomicrons are formed in the endoplasmic reticulum in the absorptive cells ( enterocytes ) of the small intestine. The villi, lined with the microvilli of the brush border, provide a lot of surface area for absorption. Newly formed chylomicrons are secreted through the basolateral membrane into the lacteals, where they join lymph to become chyle. The lymphatic vessels carry the chyle to the venous return of the systemic circulation. From there the chylomicrons supply the tissue with fat absorbed from the diet. Thus, unlike the saccharides and amino acids that digestion liberates from the carbohydrates and proteins of the diet ( respectively ), the lipids from the diet bypass the hepatic portal system, meaning the liver does not get `` first crack '' at them. Stages There are three stages in the chylomicron 's `` lifecycle '' : Nascent chylomicron Mature chylomicron Chylomicron remnant Nascent chylomicrons Triglycerides are emulsified by bile and hydrolyzed by the enzyme lipase, resulting in a mixture of fatty acids and monoglycerides. These then pass from the intestinal lumen into the enterocyte, where they are re-esterified to form triacylglycerol. The triacylglycerol is then combined with phospholipids, cholesterol ester, and apolipoprotein B - 48 to form a nascent chylomicron. These are then released by exocytosis from enterocytes into lacteals, lymphatic vessels originating in the villi of the small intestine, and are then secreted into the bloodstream at the thoracic duct 's connection with the left subclavian vein. Nascent chylomicrons are composed primarily of triglycerides ( 85 % ) and contain some cholesterol and cholesteryl esters. The main apolipoprotein component is apolipoprotein B - 48 ( apo B - 48 ). Mature chylomicron While circulating in blood, chylomicrons exchange components with high - density lipoproteins ( HDL ). The HDL donates apolipoprotein C - II ( APOC2 ) and apolipoprotein E ( APOE ) to the nascent chylomicron and, thus, converts it to a mature chylomicron ( often referred to simply as `` chylomicron '' ). APOC2 is the coenzyme for lipoprotein lipase ( LPL ) activity. Chylomicron remnant Once triglyceride stores are distributed, the chylomicron returns APOC2 to the HDL ( but keeps APOE ), and, thus, becomes a chylomicron remnant, now only 30 -- 50 nm. APOB48 and APOE are important to identify the chylomicron remnant in the liver for endocytosis and breakdown. References Jump up ^ Mahmood Hussain, M ( January 2000 ). `` A proposed model for the assembly of chylomicrons ''. Atherosclerosis. 148 ( 1 ) : 1 -- 15. doi : 10.1016 / S0021 - 9150 ( 99 ) 00397 - 4. Jump up ^ Smith, Sareen S. Gropper, Jack L. ; Smith, Jack S ( 2013 ). Advanced nutrition and human metabolism ( 6th ed. ). Belmont, CA : Wadsworth / Cengage Learning. ISBN 1133104053. Lipids : lipoprotein particle metabolism Lipoprotein particle classes and subclasses delivery of TGs : Chylomicron VLDL delivery of C and CE : IDL LDL lb LDL sd LDL Lp ( a ) HDL Remnant cholesterol Apolipoproteins APOA APOB APOC APOD APOE APOH SAA SAA1 Extracellular enzymes LCAT LIPC LPL Lipid transfer proteins CETP MTTP PLTP Cell surface receptors HDL : SCARB1 IDL : LRP LRP1 LRP1B LRP2 LRP3 LRP4 LRP5 LRP5L LRP6 LRP8 LRP10 LRP11 LRP12 LDL : LDLR LRPAP1 ATP - binding cassette transporter ABCA1 ABCG5 ABCG8 Biology portal Retrieved from `` https://en.wikipedia.org/w/index.php?title=Chylomicron&oldid=794257349 '' Categories : Lipoproteins Hidden categories : Articles needing additional references from December 2009 All articles needing additional references Talk Contents About Wikipedia Català Čeština Dansk Deutsch Eesti Español فارسی Français Galego Italiano Lietuvių Македонски മലയാളം Nederlands 日本 語 Norsk Polski Português Русский کوردی Српски / srpski Srpskohrvatski / српскохрватски Suomi Svenska Türkçe 中文 Edit links This page was last edited on 6 August 2017, at 21 : 53. 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Question: where are large lipids packaged in chylomicrons for absorption
Answer: endoplasmic reticulum