Cholesterol Metabolism Flashcards
Enzyme for the rate-limiting step in cholesterol metabolism
HMG CoA reductase
Acetoacetyl CoA + acetyl CoA = ___
3-hydroxy-3-methylglutaryl (HMG) CoA
the action of HMG CoA reductase turns HMG CoA into ___
mevalonate
Mevalonate + 2 transfers of phosphate groups from ATP
5-pyrophosphomevalonate
Sequence the formation of these compounds after 5-pyrophosphomevalonate
A.farnesyl pyrophosphate
B.isopentyl pyrophosphate
C.3,3-dimethylallyl pyrophosphate
D.geranyl pyrophosphate
B then C then D then A
B.isopentyl phosphate [5-Carbon] C.3,3-dimethylallyl pyrophosphate [5C]—(transferase)–>D. geranyl pyrophosphate [10C]–(transferase)–> A. farnesyl pyrophosphate [15C]
The combination of two farnesyl phosphate molecules yields ___, a compound with ___ Carbon atoms via the action of the enzyme __
squalene
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squalene synthase
Squalene converted (througH molecular oxygen, NADPH and the enzyme ____) to ___, a 27C compound
squalene monoxygenase
lanosterol
True or False: Lanosterol has more carbon atoms than cholesterol
false; cholesterol and lanosterol both have 27 carbon atoms
Rate limiting step @ bile acid synthesis: introduction of ____ of the steroid nucleus by the enzyme ____
hydroxyl group at C7
cholesterol-7-alpha-hydroxylase
Bile salts: bile acids conjugated to ___ or ___ by an ___ bond between the carboxyl group of the bile acid and amino group of the added compound
glycine
taurine
amide
As lipoproteins transport lipids to the different organs, there is no gradual deposition of lipids in the peripheral tissues. True or false?
false; there is gradual deposition of lipids :)
False about chylomicrons
a. assembled in the liver
b. start with apo-B-48 synthesis in the RER
c. have lower density than low-density lipoprotein
d. none of the above
a. assembled in the liver
intestinal mucosal cells dapat
apo B-48 loaded with lipid by _____ = chylomicron
microsomal triacylglycerol transfer protein
The chylomicrons released by intestinal mucosa are functionally complete, true or false?
False. They need to be rapidly modified in the plasma by apo E and apo C(from circulating HDL) to achieve full functionality.
Remnant chylomicron is processed in what organ?
a. small intestine
b. pancreas
c. liver
d. all of the above
c. liver
False about VLDL
A. high TAG content
B.more dense than CM
C. synthesized in the plasma
c. synthesized in the plasma
yung totoo: VLDL is synthesised in the liver from triacylglycerol packaged with cholesterol, apo B-100 and phospholipids
As VLDL is circulated, it VLDL decreases in size and becomes denser + exchanges materials with HDL (process catalysed by ____)
cholesteryl ester transfer protein
LDL delivers cholesterol to the peripheral tissues (or return it to the liver) by binding to cell surface membrane LDL receptors that recognize apo B-48. True or false?
False. apo B-100, not apo B-48
LDL receptors (negatively charged glycoproteins) are in pits whose shapes are stabilised by ___
clathrin
high cholesterol (stimulates, inhibits) HMG CoA reductase
inhibits
lipoprotein with highest protein content
HDL
HDL is a circulating reservoir of apolipoproteins: ___ and ___
apo C-II
apo E
main functions of HDL: uptake of ____ from ____ and return to ____ as _____
uptake of unesterified cholesterol from non-hepatic tissues and return to the liver as cholesteryl esters
Which lipoprotein is termed as “good cholesterol”?
a. VLDL
b. HDL
c. LDL
d. chylomicrons
e. all of them are termed as such
b. HDL
