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What lipoprotein is described in the lecture as causally linked to
atherosclerotic cardiovascular disease? - ANSWER ✔✔LDL.
What happens when LDL accumulates in vessel walls? - ANSWER
✔✔Lipid accumulation and inflammation promote formation of
atherosclerotic plaque.
Why should circulating LDL be kept low? - ANSWER ✔✔Because
both the magnitude and duration of LDL exposure increase ASCVD risk.
,What are the three major sources or fates emphasized for cholesterol
homeostasis? - ANSWER ✔✔Import from diet, synthesis in cells, and
oxidation to bile acids.
What is the basic building block of cholesterol biosynthesis? -
ANSWER ✔✔The isoprene unit, a C5 hydrocarbon skeleton.
What are isoprenoids? - ANSWER ✔✔Linear compounds made of
repeating C5 isoprene units.
What are terpenoids? - ANSWER ✔✔Compounds derived from the
same C5 unit that can be oxidized, cyclized, and rearranged.
How many carbons does cholesterol contain? - ANSWER ✔✔27
carbons.
How is cholesterol made from isoprene-based precursors? -
ANSWER ✔✔C5 subunits are stitched together to form a C30
precursor, then 3 carbons are removed to yield cholesterol.
What major structural class does cholesterol belong to? - ANSWER
✔✔Steroids.
What is the steroid framework of cholesterol? - ANSWER ✔✔Three
fused 6-membered rings and one fused 5-membered ring.
,What does alpha mean in steroid nomenclature? - ANSWER ✔✔A
substituent below the plane of the molecule.
What does beta mean in steroid nomenclature? - ANSWER ✔✔A
substituent above the plane of the molecule.
What ring conformations are common in steroids? - ANSWER
✔✔Chair and boat conformations.
How do hydroxyl groups affect steroid properties? - ANSWER
✔✔They make steroids more hydrophilic.
How do ketones affect steroid properties relative to hydroxyl groups? -
ANSWER ✔✔Ketone-containing steroids are often more
hydrophobic.
What is the starting precursor for cholesterol biosynthesis? -
ANSWER ✔✔Acetyl-CoA.
Where does acetyl-CoA come from according to the lecture? -
ANSWER ✔✔Fatty acid breakdown in mitochondria and sugar
breakdown through glycolysis.
How many acetyl-CoA molecules are linked to form HMG-CoA? -
ANSWER ✔✔Three.
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, What enzyme converts HMG-CoA to mevalonate? - ANSWER
✔✔HMG-CoA reductase.
What kind of reaction does HMG-CoA reductase catalyze? -
ANSWER ✔✔Reduction of a thioester to a primary alcohol.
What reducing agent is used by HMG-CoA reductase? - ANSWER
✔✔Two molecules of NADPH.
What is the rate-limiting step in cholesterol biosynthesis? - ANSWER
✔✔Conversion of HMG-CoA to mevalonate by HMG-CoA reductase.
Where is HMG-CoA reductase located? - ANSWER ✔✔In the ER
membrane.
What is the first phosphorylation step after mevalonate formation? -
ANSWER ✔✔Mevalonate is converted to phosphomevalonate.
What enzyme carries out the first phosphorylation of mevalonate? -
ANSWER ✔✔Mevalonate-5-phosphotransferase.
What is the second phosphorylation step in the mevalonate pathway? -
ANSWER ✔✔Phosphomevalonate is converted to 5-
pyrophosphomevalonate.