Cholesterol Flashcards
cholesterol ( sterol) has hydroxyl group at which carbon?
C-3
cholesterol is converted to ___ for storage/tansport in blood
cholesteryl esters
rate limiting step in cholesterol biosynthesis?
HGM-CoA reductase
2NADPH used 2 NADP+ out
3 regulation for HMG-CoA reductase
- transcriptional control
- degradation
- covalent modification
how HGM-Coa reductase is transcriptionally regulated?
high CH level -> SCAP-SREBP-DNA binding domain + cholesterol are stucked in ER membrane
when CH level low -> SCAP-SREBP-DNA binding domain are moved to golgi. Protease comes cleaves and DBD goes into nuclues
how HGM-Coa reductase is covalently modificated?
glucagon (increase phosphorylation) -> inactive
insulin (phosphatases) –> activate to make CH
first step of cholesterol synthesis
3 acetyl coa -> mevalonate (6C)
second step of cholesterol synthesis
mevalonate –> isoprene or isoprenoid
6C - > 5C (lose CO2)
3rd step of cholesterol synthesis
6 isoprene -> geranyl(C10) -> farnesyl(C15) -> squalene(C30)
4rd step of cholesterol synthesis
cyclize linear suqalene and modify it to make cholesterol
Farnesyl - PP and geranyl are used to make ___
dolichol, heme A, ubiquionone, vit D, other sterols
some is esterified by ___ and packaged into VLDL and shipped out to cells needing CH
ACAT (Acyl-coa-Cholesterol Acyl Transferase)
COOH group of bile salts can be ___ to glycine or taurine
conjugated
(turning into hydrophilic state)
ileum reabsorbs over 95% of bile salts
bile salt synthesis : -OH @ 3, 7
chenocholate
bile salt synthesis : -OH @ 3,7,12
cholate
can you digest/metabolize cholesterol? (degrade into CO2)?
NO
<5% loss of bile salts is critical for getting rid of bilesalts
this thought to bind CH/bile salts and remove even more
fiber
cholesterol is precursor of five classes of steriod hormones
glucocorticoids mineralocorticoids androgens estrogens progestins
what are the two lipoprotein cholesterol diseases?
gall stone (cholesterol:phospholid > 1:1) atherosclerosis ( ingestion oxidized LDL -> foam cell)
two drugs that are used for lipoprotein/cholesterol disease
cholestyramine (lower plasma cholesterol level)
ezetimibe (selectively inhibit reabsorption of CH “specific”)(
drug to inhibit HGM-CoA reductase
Statins
lovastatin(lactone) blockes reductase
disease due to deficiency of mevalonate kinase
mevalonic aciduria
hyperimmunoglobulinemia D
periodic fever syndrome
