BILE SALTS AND STEROID
BIOSYNTHESIS EXAM WITH COMPLETE
QUESTIONS AND ANSWERS { GRADED
A+}
Sources of Cholesterol - ✔✔cholesterol from the diet is absorbed as
chylomicron remnants; cholesterol from extrahepatic tissues are
absorbed as HDL; and de novo cholesterol synthesis occurs in the liver
How Cholesterol Leaves the Liver - ✔✔from the liver cholesterol pool,
leaves via the secretion of VLDL, as free cholesterol secreted in the bile
and conversion to bile acid/salts
, Bile Salt Synthesis - ✔✔1. an a-hydroxyl group is added to carbon 7 of
cholesterol, catalyzed by rate limiting 7a-hydroxylase; inhibited by bile
salts
2. the double bond of cholesterol is reduced and further hydroxylation
occurs, resulting in a compound with two a-hydroxyl groups at carbons
3 and 7, and the other with three a-hydroxyl groups at carbons 3,7 and
12
3. the side chain is oxidized and converted to a branched, five carbon
chain containing a carboxylic acid at the end producing primary bile
salts
Primary Bile Salts - ✔✔the diol bile caid is chenocholic acid and the
triol bile caid is cholic acid; these are salts when ionized and thus
carrying a negative charge at a pH above 6
Conjugation of Bile Salts - ✔✔the bile salts are activated by ATP and
CoA forming their CoA derivatives which can form conjugates with
either glycine or taurine
BIOSYNTHESIS EXAM WITH COMPLETE
QUESTIONS AND ANSWERS { GRADED
A+}
Sources of Cholesterol - ✔✔cholesterol from the diet is absorbed as
chylomicron remnants; cholesterol from extrahepatic tissues are
absorbed as HDL; and de novo cholesterol synthesis occurs in the liver
How Cholesterol Leaves the Liver - ✔✔from the liver cholesterol pool,
leaves via the secretion of VLDL, as free cholesterol secreted in the bile
and conversion to bile acid/salts
, Bile Salt Synthesis - ✔✔1. an a-hydroxyl group is added to carbon 7 of
cholesterol, catalyzed by rate limiting 7a-hydroxylase; inhibited by bile
salts
2. the double bond of cholesterol is reduced and further hydroxylation
occurs, resulting in a compound with two a-hydroxyl groups at carbons
3 and 7, and the other with three a-hydroxyl groups at carbons 3,7 and
12
3. the side chain is oxidized and converted to a branched, five carbon
chain containing a carboxylic acid at the end producing primary bile
salts
Primary Bile Salts - ✔✔the diol bile caid is chenocholic acid and the
triol bile caid is cholic acid; these are salts when ionized and thus
carrying a negative charge at a pH above 6
Conjugation of Bile Salts - ✔✔the bile salts are activated by ATP and
CoA forming their CoA derivatives which can form conjugates with
either glycine or taurine
