lipid metab

Question 1

cholesterol synthesis: LCAT and HMG CoA reductase. What do both do?

Answer 1

rate-limiting step catalyzed by HMG-CoA reductase (induced by insulin). this converts HMG-CoA to mevalonate. most plasma cholesteral is esterified by LCAT. LCAT also plas a crytical role in in converting nascent HDL to mature HDL

Question 2

Statins: target, mechanism (competitive/non-competitive; reversible, irreversible)

Answer 2

competitively and reversibly inhibit HMG-CoA reductase, the rate-limiting step for cholesterol synthesis

Question 3

Pancreatic lipase: function, location

Answer 3

responsible for the degradation of dietary triglycerides in the small intestines

Question 4

lipoprotein lipase: function, location

Answer 4

degrades TGs circulating in chylomichrons (which are absorbed from the intestines) and VLDL (very low density lipoprotein). found on vascular endothelial surface

Question 5

hepatic TG lipase

Answer 5

degradation of TGs remaining as intermediate density lipoprotein

Question 6

CETP

Answer 6

cholesterol ester trasnfer protien mediates the transfer of cholesterol esters to other lipoprotein particles. Important enzyme that transfers cholesterol esters to VLDL, IDL, and LDL from mature HDL.

Question 7

exogenous lipid transport

Answer 7

dietary lipids are absorbed in the GI tract, and converted to chylomicrons in intestinal mucosa. chylomicrons then enter the general circulation, where they are processed by lipoprotein lipase. the end result are chylomicron remnants, which are taken up by the liver

Question 8

endogenous lipid transport

Answer 8

liver synthesizes VLDL (very low density lipids). VLDL carries fat to tissues. VLDL may be converted to LDL, which can be taken up by periphery or again by lipids.

Question 9

HDL

Answer 9

synthesized in blood from various souces. picks up peripheral cholesterol and transports it back to the liver. aka scavenging protein.

Question 10

Apolipoprotein E function, relevant molecs.

Answer 10

mediates remnant reuptake. seen chylomicrons, chylomicron remnants, VLDL, IDL, and HDL

Question 11

apolipoprotein A-1 function, relevant molecs.

Answer 11

activates LCAT (which esterifies cholesterol). works on chylomicrons and HDL

Question 12

apolipoprotein C-II function, relevant molecs.

Answer 12

lipoprotein lipase cofactor (LPL is found on the vascular endothelium and degrades triglycerides and VLDL. also works on HDL

Question 13

poplipoprotein B-48 function, relevant molecs.

Answer 13

mediates chylomicron secretion. affects chylomicrons and chylomicron remnants

Question 14

apolipoprotein B-100. function, relevant molecs.

Answer 14

binds LDL receptor. affects VLDL, IDL, and LDL.

Question 15

LDL: formation/secretion, what they do

Answer 15

synthesized by liver and transports cholesterol from liver to tissues.

Question 16

VLDL: formation/secretion, what they do

Answer 16

delivers hepatic triglycerides to peripheral tissues

Question 17

IDL: formation, what they do

Answer 17

formed in the degradation of VLDL (and chylomicrons). delivers TGs and cholesterol to the liver. (IDL that isn’t taken up by the liver becomes LDL)

Question 18

chylomicrons: function, who secretes them

Answer 18

delivers dietary TGs to peripheral tissue. delivers cholesterol to liver in the form of chylomicron remnants. secreted by intestinal epithelial cells.