Cholesterol & Steroids Flashcards
cholesterol synthesis requires
acetyl CoA, NADPH, & ATP
rate limiting enzyme for cholesterol synthesis
HMG CoA reductase
where does cholesterol synthesis occur
cytoplasm
steps of acetyl coA to HMG coA
2 acetyl CoA to acetylacyl CoA via thiolase. acetylacyl CoA to HMG CoA via HMG CoA synthase
function of HMG CoA reductase
takes HMG CoA to mevalonate. uses 2 NADPH. irreversible step because it releases CoA
inhibitors of HMG CoA reductase
cholesterol, statins, glucagon.
activator of HMG CoA reductase
insulin
explain sterol independent inactivation of HMG CoA reductase
high levels of AMP activate AMPkinase to phosphorylate HMG CoA reductase and render it inactive.
statins are what kind of inhibitors of HMG CoA reductase
competitive
low cholesterol promotes the release of which stimulatory protein
SREBP (causes the liver to produce more HMG CoA reductase)
degradation of HMG CoAR due to high levels of cholesterol or Mevalonate, is done by
proteosomes tagging with ubiquitin
lipoprotein with highest amount of cholesterol
LDL
increases the amount of LDL receptors on the cell surface to lower serum LDL
statins
converts cholesterol to cholesterol ester for storage
ACAT
enzyme needed for double bond formation in the b ring of cholesterol
7-dehydrocholesterol reductase
disorder associated with absent 7-dehydrocholesterol reductase
SLOS- causes severe mental retardation
some cholesterol is modified by bacteria to form
cholestanol & coprostanol
