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32 Cards in this Set
- Front
- Back
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What is a lipoprotein particle composted of?
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1. Outer monolayer of phospholipids.
2. Free or un-esterified cholesterol (i.e. with -OH group) 3. Proteins - KA Apoproteins - that are amphipathic 4. Triacylglycerol and cholesteryl esters in the core. |
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Rank in order the Density of lipoprotein particles from lowest to highest density. Do the same for diameter size:
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Chylomicron < VLDL < IDL < LDL < HDL. It's the reverse for diameter.
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What are the two roles for proteins in Lipoprotein Particles?
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1. They solubilize hydrophobic lipids
2. They contain cell targeting signals. |
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In regard to what component is High Density in HDL? FYI - she is holding us responsible for knowing the relative percentages for protein, cholesterol esters, and triacylglycerols. p 252
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The protein.
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Where are Chylomicrons assembled and where are they secreted? What are their defining proteins?
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Chylomicrons are assembled in the intestine and secreted by enterocytes. Defining proteins are ApoB-48 and ApoA
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Summarize how chylomicrons are made - starting with dietary triacylglycerols.
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Triacylglycerols are ingested -> in small intestine, it is emulsified by bile acids -> pancreatic lipase hydrolyzes FA from positions 1 and 3 producing free FA (FFA) and 2-monoacylglycerol (2-MG) in the lumen. FFA and 2MG are taken up by enterocytes where triacylglycerol is resynthesized. The enterocytes then package the triacylglycerol into chylomicrons which are secreted by the cells.
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Where does chylomicron get the apolipoprotein that is recognized by lipoprotein lipase? (p253)
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ApoC-II come from HDL
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What does lipoprotein lipase bind to to become a membrane bound enzyme? (p253) And what type of cells does it typically bind to?
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It binds to heparin sulfate proteoglycan. Typically binds to Adipose and Muscle tissue.
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Lipoprotein lipase requires recognition what lipoprotein molecule to function?
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ApoC-II
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In the liver, what apolipoprotein does hepatic lipase recognize to break down TG's left over in the chylomicron?
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ApoE
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What is VLDL assembled by? By what is it secreted? What are its defining proteins?
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VLDL is assembled in the liver. Secreted by hepatocytes. ApoB-100, ApoC-11, ApoE
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Review/understand this slide. See "Biochem/Lectures/Block 3/slide p253 Review.docx
for notes |
Review/understand this slide. See "Biochem/Lectures/Block 3/slide p253 Review.docx
for notes |
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Where is ACAT found and what does it do?
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ACAT is found inside liver cells and it adds a fatty acid to the hydroxyl group of cholesterol for the purposes of packaging.
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Note: Chylomicrons come from enterocytes whereas VLDL comes from Liver. So, much of TGs in these come from different places - chylo from diet, VLDL from various sources in the liver. What are the three major places the liver gets TGs that it packages into VLDL?
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1. de novo lipogenesis
2. plasma free fatty acids 3. chylomicron remnants |
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What is IDL derived from? What proteins define it? What is it enriched in? (p254)
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Derived from VLDL following removal of TGs by lipoprotein lipase. Defined by apoB-100, apoC-II, apoE. It is enriched in Cholesteryl Esters.
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What is LDL derived from? What proteins define it? What is in enriched in?
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Derived from IDL following removed of triacylglycerol by hepatic lipase. Defined by apoB-100. Highly enriched in Cholesteryl Esters.
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What is Forward Cholesterol Transport and what is the major player? How is this possible? p255
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It is transport of cholesterol to the periphery - major player is LDL. Since LDL is missing most of its ApoE, it is not readily absorbed by the LDL receptor in the liver and therefore free to circulate.
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LDL is the end product of the metabolism of VLDL by the action of two enzymes - what are they and what lipoproteins do they recognize? (p255)
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Lipoprotein Lipase (ApoC-II) and Hepatic Lipase (ApoE - ultimately, this protein is removed by the time VLDL become LDL - and that's why LDL can function as a forward cholesterol transporter and not readily absorbed by LDL receptor in liver).
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Why does IDL have a much lower half-life in circulation compared to LDL?
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BC IDL has ApoE which has a much higher affinity for the LDL receptor than the ApoB-100 protein that LDL has.
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Review the differences between LDL and IDL at the bottom of pg 254 - it's good.
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Review the differences between LDL and IDL at the bottom of pg 254 - it's good.
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The bulk of LDL receptors are found in what type of cells?
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Hepatocytes.
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If LDL is responsible for forward cholesterol transport, what is responsible for reverse cholesterol transport?
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HDL
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Where is HDL assembled? What proteins define it?
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The liver and small intestine. ApoA-1, apoC-II, apoE define it.
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HDL contains three additional proteins that enable it to remodel other lipoproteins - what are they?
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1. Phospholipid transfer protein (PLTP)
2. Cholesteryl ester transfer protein (CETP) 3. Lecithin-cholesterol acyl transferase (LCAT) |
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What is the role of PLTP?
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It mediates the transfer of phospholipid and cholesterol into HDL.
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What is the role of CETP?
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It mediates the removal of cholesteryl esters (CE) from HDL.
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What is role of LCAT?
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It associates with HDL to esterify cholesterol to cholesteryl esters, which is more suited for packaging inside the HDL particle.
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Why is HDL considered the good lipoprotein?
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Because it transports cholesterol from the periphery to the liver for elimination.
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What is the role of ATP-binding cassette transporter (ABCA1)? (p256)
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It delivers cholesterol to ApoA-1, forming a nascent HDL
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What is the role of SR-B1 (scavenger receptor B1)
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It functions on liver or cells active in steroid synthesis and binds to HDL for uptake.
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Review p256 - make sure you know how HDL works with it's various enzymes, etc.
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Review p256 - make sure you know how HDL works with it's various enzymes, etc.
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What is the only difference between LCAT and ACAT?
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ACAT is found inside cells while LCAT is found in the blood where it circulates associated with HDL. They both esterify free cholesterol (i.e. with an -OH) with a fatty acyl residue of phosphoatidylcholine (Lecithin)
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