WVSOM - Biochem

Description:	Cholesterol and Bile Acid Synthesis
Category:	Biochemistry
Created by:	null on 2008-10-17

Question	Answer
Cholesterol Synthesis Starting materials	Acetyl CoA NADPH ATP
HMG-CoA reductase	rate limiting step (target of drug therapy)
Products of cholesterol synthesis	Cholesterol NADP+ ADP
Location of Cholesterol synthesis	hepatocytes
regulated enzyme of cholesterol synthesis	HMG CoA reductase
Increasing levels of cholesterol __________ cholesterol synthesis	decreases
HMG CoA is active when	dephosphorylated
HMG CoA is dephosphorylated with ___________ insulin to glucagon levels.	high
HMG CoA is inactivated by ____________ and is then _____________	Glucagon; phosphorylated
Most significant factor in regulation of cholesterol biosynthesis	decreasing HMG CoA reductase synthesis
Proteolysis of HMG CoA reductase increases as ____________	sterol levels rise
Which drug class inhibits this enzyme	statins
Extrahepatic cholesterol synthesis	occurs under certain pathological conditions
Why is cholesterol esterified	regulation
where is cholesterol esterified	on lipoprotiens and in cells
How does esterification change regulation	cholesterol ester CANNOT regulate HMG CoA reductatse
Two enzymes that esterize cholesterol	LCAT (Lecithin) ACAT (acyl CoA)
LCAT	Esterifies cholesterol on lipoprotein that can be transferred from HDL to LDL
ACAT	esterifies cholesterol within the cell
Extrahepatic cholesterol synthesis	under certain pathological conditions
Where are cholesterol esterified/de-esterified in cells?	lipoproteins
Esterifcation of cholesterol	changes the properties of cholesterol especially with regard to its control functions
LCAT	Lecithin: chelesterol acyl transferase Esteerifies cholesterol on lipoproteins
What is transfered to LDL and HDL	Esterfied cholesterol
ACAT	esterfies cholesterol within the cell
Cholesterol esterase	reveses LCAT and ACAT esterification
Bile Salt Synthesis Location	hepatocytes
Starting compounds of Bile Salts	Cholesterol, ATP, NADPH
4 conjugated bile salts	taurocholic glycocholic taurochenocholic glycohenocholic acids
Conjugation of bile salts increases ____________	solubility
Solubility enables bile salts to act as	detergents
Conjugated bile salts composed of	primary bile salts, cholic acids and chenocholic ascid conjugated to taurine or glycine which are hydrophobic
How much bile salts are recycled	> 95%
Liver synthesis of bile acid _____ g/day	.2 - .6
Amount of bile salts reabsorbed	12-32 g/day
bile removed by feces	.2-.6 g/day
Why would we want to decrease bile salt reabsorption	drugs which bind to bile acids prevent their reabsorption to increase cholesterol excretion
Cholesterol esterase	reverses LCAT and ACAT by de-esterifying cholesterol
Bile Salt Exrection	in feces
Primary Bile Salts	chenocholic acid and chlic acid
Location of bile acid synthesis	hepatocytes
starting compounds of bile acid synthesis	cholesterol ATP NADPH
Controlled step of bile acid salts	products and substrate!!!!
Products of bile acid synthesis	cholic acid and chenocholic acids
Conjugated bile salts	primary bile salts bound to hydrophobic taurine or glycine
4 conjugated bile salts	taurocholic glycocholic taurochenocholic glyochenocholic acids
Bile Salts recycled	> 95% 12-32 g/day
Why would we want to pharmachologically bind drugs to bile acids	to prevent reabsorption to increase cholesterol excretion