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44 Cards in this Set

  • Front
  • Back
Cholesterol structure explains its ____ water solubility
low
Cholesterol is derived from both ______ and the _____
endogenous synthesis
diet
Cholesterol is made from _____.
acetyl-CoA
Step 2 in the pathway above (_______) is the committed and regulated step of the pathway.
HMG-CoA reductase
HMG-CoA reductase is feedback-inhibited by _______ at the transcriptional and enzyme levels
free cholesterol
______ stimulates HMG-CoA reductase.
insulin
Our bodies contain 140 g of cholesterol, most of it in __________.
nervous tissue
Dietary cholesterol is esterified by the intestinal mucosal enzyme _______.
acyl-CoA-cholesterol acyl transferase (ACAT)
Cholesterol is very insoluble in water, but esterified cholesterol is even more insoluble, hence _______ before packaging.
esterification
After uptake by intestianal brush border cells, half of it, both cholesterol and cholesterol esters are packaged together with dietary triglycerides and lipoprotein into _________.The other half is disposed of with the stool after conversion to neutral sterols by bacteria. nearly 500 mg of unmetabolized cholesterol can be eliminated from the body per day!
chylomicrons
The stuff in chylomicrons enters the enterohepatic circulation. First chylomicrons deposit their content of tryilycerides to _________ (after broken down to fatty acids by cellular lipoprotein lipase
peripheral tissue
The remainder of the chylomicron particle is funneled to the ______(requires HDL).
liver
In the liver, it goes in one of three ways:
packaging in VLDL, conversion to bile acids and flow with bile, or direct deposit of cholesterol itself into the bile and from there to intestine again.
VLDL is secreted from the liver, remodeled into ____ in the blood
LDL
The LDL is the primary form of cholesterol that is uptaken by peripheral cells which use it mainly to make their _______.
membranes
Bile acids are made in the liver and deposited in the ________
gallbladder
Half of the gallbladder cholesterol is absorbed by the _______.
intestine
half of the liver’s pool of cholesterol is eventually metabolized to the _______ in the liver.
primary bile acids
Bile acids are required for absorption of _________ by the intestinal brush border.
long-chain fatty acids
These primary bile acids are then conjugated with _____ or _____ in the liver to increase their amphipathic nature and miscibility with fatty acids (needed in the intestine) and dumped into the bile, stored in the gallbladder.
glycine
taurine
The deconjugated bile acids 96% are absorbed by a __________ mechanism in the ileum and returned to the liver. The liver conjugates them secretes them again in the bile.
sodium cotransport
Upon eating a fatty meal, the gallbladder contracts (via hormonal signal) to release ______ into the intestinal lumen.
Bile
Intestinal bacteria ______ bile acids in the intestine.
Deconjugate
________of bile acids are made by the liver. They circulate 5-8 times daily, amounting to 20 g/day of secreted bile acids.
0.5 g / day
When bile flow is blocked due to gallstones, bile piles up in the liver and seeps to the _____
blood
Elevated plasma levels of ______is indicative of liver disease or gallstones.
bile acids
steroid nucleus of cholesterol cannot be degraded in the human body.
Cholesterol has to be disposed of by the biliary system, either as such or after conversion to bile acids. half of the cholesterol is eventually metabolized to ______ in the liver. Conjugation makes them more water soluble.
primary bile acids
The committing step in bile synthesis is _______and the synthesis is feedback-inhibited by ________.
7α-hydroxylase
bile acids
This is a monooxygenase reaction and requires molecular____, _____, and _____-.
oxygen
NADPH
cytochrome P-450
_________also seems to be involved. Deficiency (scurvy) impairs the formation of bile acids and causes cholesterol accumulation and atherosclerosis.
Ascorbate
Regulation of bile synthesis takes place in four ways:
1. ________ (the product) reduce the level of 7α-hydroxylase by inhibiting the transcription of its gene.
2. _______ (the substrate), in contrast, induces 7α-hydroxylase synthesis transcriptionally.
3. Bile acids also reduce the activity of ______, the enzyme that makes cholesterol. Less cholesterol means less 7a-hydroxylase.
4. _______ induce the synthesis of 7α-hydroxylase. This effect contributes to the increased plasma cholesterol level in patients with hypothyroidism.

These regulatory effects ensure the maintenance of an adequate pool of free cholesterol in the liver.
Bile acids
Cholesterol
HMG-CoA reductase
Thyroid hormones
Cholesterol precipitates and forms gallstones when bile cholesterol level is too _____, or levels of the emulsifying lipids are too ____
high
low
Normal composition of bile is at *: ____ molecules of cholesterol for every ___ molecules of lecithin and _____ molecules of bile acid.
10
5
85
Major bile constituents:
lecithin (phosphatidylcholine) as emulsifying lipid, bile acids (in salt form), cholesterol.
Gallstones afflict 20% of all people in Western countries, most commonly ____ _____ ______
fat, fertile females.
10% of gallstones consist of substances other than cholesterol, usually bilirubin and other bile pigments, hence ________
“pigment stones.”
Symptoms of gallstones (4):
severe pain, intolerance for fatty foods, sometimes hyperbilirubinemia, itching due to accumulation of bile salts in the skin.
(2/3 patients with gallstones are asymptomatic).
Diagnosis of gallstones
ultrasound.
Treatement of gallstones:
cholecystectomy or oral administration of large amounts of chenodeoxycholic acid (unconjugated bile acid) to solubilize cholesterol.
Bile acids are required for absorption of _________ by the intestinal brush border.
long-chain fatty acids
These primary bile acids are then conjugated with _____ or _____ in the liver to increase their amphipathic nature and miscibility with fatty acids (needed in the intestine) and dumped into the bile, stored in the gallbladder.
glycine
taurine
The deconjugated bile acids 96% are absorbed by a __________ mechanism in the ileum and returned to the liver. The liver conjugates them secretes them again in the bile.
sodium cotransport
Upon eating a fatty meal, the gallbladder contracts (via hormonal signal) to release ______ into the intestinal lumen.
Bile
Intestinal bacteria ______ bile acids in the intestine.
Deconjugate