Cholesterol Flashcards
what are the sources of cholesterol
diet and de novo synthesis
what is cholesterol required for
synthesis of bile salts and vitamin D
synthesis of steroid hormones
appropriate myelination of nerves
what does de novo synthesis of cholesterol require
acetyl CoA
NADPH
ATP
carbon donor
reducing power
energy source
where does de novo synthesis occur
the cytosol but some enzymes are bound to membrane of the ER
how much does 1 mole of cholesterol require
18 moles of acetyl CoA
16 moles of NADPH
36 moles of ATP
what are the 4 phases of de novo synthesis called
synthesis of mevalonic acid
synthesis of farnesyl pyrophosphate
synthesis of squalene
synthesis of cholesterol
what is HMG CoA reductase (step 1)
rate limiting step in cholesterol biosynthesis
what does HMG CoA reductase do (step 1)
catalyzes the reduction of HMG CoA to mevalonate
what are statins
inhibitors of HMG CoA reductase
describe the cyclization of squalene (step 4)
cyclization of squalene to form the 4 sterol ring in the 30C lanosterol
what is lanosterol converted to
cholesterol (27C)
what does the conversion to cholesterol involve
the removal of 3 methyl groups and rearrangement of some double bonds that require the oxidation of NADPH
how is cholesterol biosynthesis regulated
-cholesterol inhibits HMG CoA reductase activity particularly in the liver
-cholesterol activates fatty acyl CoA : cholesterol acyltransferase (ACAT)
where is ACAT and what do they do
in the hepatocytes
promotes formation of cholesterol esters (accumulates in the liver)
