Final: cholesterol metabolism Flashcards
cholesterol purpose
maintains cell membrane
makes steroid hormones, bile acids, and vitamin D
cholesterol synthesis location
smooth endoplasmic reticulum
cholesterol synthesis step 3
HMG-CoA to mevalonate
enzyme: HMG-CoA reductase
2 NADPH +2 H+ to 2 NADP+
releases CoA-SH and H2O
rate limiting step of cholesterol synthesis
HMG-CoA reductase step
cholesterol synthesis overview
2 acetyl-CoA to cholesterol
where is majority of cholesterol made and used?
the liver!
makes bile acids
how does cholesterol move through the bloodstream?
it needs lipoproteins bc it is insoluble in water
what other organs use cholesterol?
adrenal glands and gonads use cholesterol to make steroid hormones
when do we want to turn off the cholesterol pathway?
never!
methods of cholesterol regulation
1) HMG-CoA reductase
2) allosteric effects by covalent modification
HMG-CoA reductase control
short-term: by energy competitors, allosteric binding and hormone effects
long-term: synthesis and degradation
HMG-CoA reductase kinase aka
AMPK
HMG-CoA reductase is active when
it is not phosphorylated
HMG-CoA reductase is inactive when
it is phosphorylated
Low energy leads to
decreased HMG-CoA reductase and decreased cholesterol synthesis
