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17 Cards in this Set
- Front
- Back
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Describe Lipoproteins, generally speaking.
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Spherical particles with a hydrophobic core (TG and esterfied cholesterol)
On the surface, you have Apolipoproteins: - large: apoB (B-48, B-100) - small: apoA-I, apoC-II, apo-E ...they're like address particles. they're all classified on the basis of density and electrophoretic mobility. |
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List VLDL, LDL, IDL, and HDL in order of increasing size. Where do chylomicrons fit?
What about by density? |
HDL --> LDL --> IDL --> VLDL --> Chylomicrons
opposite order. |
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Describe the difference between integral apoproteins and peripheral apoproteins.
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integral are a part of the phospholipid wall, peripherals are just stuck to it.
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Given the apo's here, tell where they occur:
- A-I - A-II - A-IV - B-48 - B-100 |
- principal of HDL, activates LPL
- dimer in HDL, enhances hepatic lipase activity - in HDL, actv LCAT and LPL - ONLY in chylomicron; derived from B-100 thru alternate splicing --> lacks LDL receptor b/ domain. - principal protein in LDL, also in VLDL, IDL and Lp(a). It's the ligand for the LDL receptor. |
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Given the apo's here, tell where they occur:
- C-I - C-II - C-III - D - E - (a) |
- VLDL, HDL, chylo; actv LCAT
- ".."; actv LPL - chylo, VLDL, HDL, IDL; *inhibits* LPL - HDL; possibly actv CETP - chylo, VLDL, HDL, IDL; b/ LDL receptor - found in Lp(a) that is covalently bound to B-100 |
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Trace the hx of Discoidal (pre-B-HDL).
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- formed i/ liv and int.
+ chol, PL, AI, AII, E + disc-shaped - interacts w/ chylomicron remnants and LCAT (lecithin-chol acyl transferase) to form *spherical* a-HDL-3. + chol, CE, PL, A, E - interacts with the cell plasma membranes --> removes free chol. - LCAT converts HDL-3 to HDL-2a (higher apoE and CE content) - CETP mediates TriG/CE exchange between HDL-2a and VLDL --> HDL-2b (TriG rich) |
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What are the functions of HDL?
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- transfers proteins to other lipoproteins
- picks up lipids from other lipoproteins - converts chol --> CE via LCAT - transfers CE to other lipoproteins which then get them back to the liver. |
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What is "reverse cholesterol transport"?
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The process thru which chol-CE by HDL, and then CE gets given to other lipoproteins to take back to the liver.
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What is Lp(a)? What is (a)?
- what weird protein domain does it have? - high risk associations with clinical sequelae? |
LDL + (a); (a) = apoA linked covalently to apoB-100 by disulfide.
- kringle protein domain: tri-looped w/ 3 intramolecular disulfide bonds --> looks like a pretzel. - High risk association w/ premature CAD and stroke. |
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What is discoidal HDL or pre-B-HDL?
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contains cholesterol, phospholipid, apoA-I, apoA-II, apoE and is disc shaped;
it is formed in liver and intestine it interacts with chylomicron remnants and lecithin-cholesterol acyl transferase (LCAT) to form more spherical a-HDL3 |
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What does the chylomicron remnant receptor recognize?
LDL-R? Main site of actv? Which apo does it recog most easily? |
apoE
particles containing B-100 and/or E - liver - E > B-100 |
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Name the places in the body where cholesterol degredation takes place? What is chol converted into?
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ONLY in the liver.
Cholesterol --> Bile Acids |
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Where in the body does biosynth of cholesterol take place? Precursor in main site of synth?
- inhib of synth at this site? |
liver and intestine.
- primarily liver - acetyl CoA (Acetate) - LDL uptake by liver. |
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What is the rate-limiting step in chol biosynth?
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HMG-CoA reductase catalyzing HMG-CoA --> mevalonate.
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Rate limiting step in bile acid synthesis?
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cholesterol --> 7-a-chol by 7-a-hydroxylase
(aka CYP 7a1) |
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What % of bile acids are reabsorbed? Where does this occur?
What is the name we give to this circulation? Where is dietary fat absorbed? |
98-99% in the ileum; return to liver by way of portal circulation.
enterohepatic circulation 1st 100cm of the small intestine. |
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What do Bile salts do?
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- emulsify fats
- aid in absorption of fat soluble Vits. - accelerate pancreatic lipase actv. - stim liver to secrete bile - stim intestinal motility - keep cholesterol in solution (as micelles) |
