An individual is suspected of having a deficiency in branched-chain ketoacid
dehydrogenase. Supplementation of which of the following vitamins or cofactors may
help resolve this issue?
A. Tetrahydrobiopterin (BH4)
B. Thiamine
C. Cobalamin
D. Folate
,Give this one a try later!
B. Thiamine
(Feedback: Much like the pyruvate dehydrogenase complex, the branched
chain keto acid dehydrogenase also requires the cofactor thiamine.)
Which of the following will be elevated in the bloodstream about 4 hours after eating a
high-fat meal?
A. Low-density lipoprotein
B. High-density lipoprotein
C. Ketone bodies
D. Nonesterified fatty acids
E. Very-low-density lipoprotein
Give this one a try later!
E
(Explanation: Chylomicrons and their remnants are cleared from the
circulation rapidly after a meal, and the secretion of very low density
lipoprotein by the liver then increases. Ketone bodies and nonesterified fatty
acids are elevated in the fasting state.)
Identify the metabolite that does NOT serve as a precursor of a dietarily essential amino
acid:
A. α-Ketoglutarate
B. 3-Phosphoglycerate
C. Glutamate
D. Aspartate
E. Histamine
Give this one a try later!
, E
(Explanation: Histamine is a catabolite, not a precursor, of histidine.)
Inactivation of acetyl-CoA carboxylase is favored WHEN:
A. Cytosolic citrate levels are high.
B. It is in a polymeric form.
C. Palmitoyl-CoA levels are low.
D. The tricarboxylate transporter is inhibited.
E. It is dephosphorylated.
Give this one a try later!
D
(Explanation: Inhibition of the tricarboxylic acid transporter causes levels of
citrate in the cytosol to decrease and favors inactivation of the enzyme.)
Which one of the following statements concerning the biosynthesis of cholesterol is
CORRECT?
A. The rate-limiting step is the formation of 3-hydroxy-3-methylglutaryl-CoA (HMG-CoA)
by the enzyme HMG-CoA synthase.
B. Synthesis occurs in the cytosol of the cell.
C. All the carbon atoms in the cholesterol synthesized originate from acetyl-CoA.
D. Squalene is the first cyclic intermediate in the pathway.
E. The initial substrate is mevalonate.
Give this one a try later!
C
(Explanation: Cholesterol is synthesized in the endoplasmic reticulum from
acetyl CoA. The rate-limiting step is the formation of mevalonate from 3-
dehydrogenase. Supplementation of which of the following vitamins or cofactors may
help resolve this issue?
A. Tetrahydrobiopterin (BH4)
B. Thiamine
C. Cobalamin
D. Folate
,Give this one a try later!
B. Thiamine
(Feedback: Much like the pyruvate dehydrogenase complex, the branched
chain keto acid dehydrogenase also requires the cofactor thiamine.)
Which of the following will be elevated in the bloodstream about 4 hours after eating a
high-fat meal?
A. Low-density lipoprotein
B. High-density lipoprotein
C. Ketone bodies
D. Nonesterified fatty acids
E. Very-low-density lipoprotein
Give this one a try later!
E
(Explanation: Chylomicrons and their remnants are cleared from the
circulation rapidly after a meal, and the secretion of very low density
lipoprotein by the liver then increases. Ketone bodies and nonesterified fatty
acids are elevated in the fasting state.)
Identify the metabolite that does NOT serve as a precursor of a dietarily essential amino
acid:
A. α-Ketoglutarate
B. 3-Phosphoglycerate
C. Glutamate
D. Aspartate
E. Histamine
Give this one a try later!
, E
(Explanation: Histamine is a catabolite, not a precursor, of histidine.)
Inactivation of acetyl-CoA carboxylase is favored WHEN:
A. Cytosolic citrate levels are high.
B. It is in a polymeric form.
C. Palmitoyl-CoA levels are low.
D. The tricarboxylate transporter is inhibited.
E. It is dephosphorylated.
Give this one a try later!
D
(Explanation: Inhibition of the tricarboxylic acid transporter causes levels of
citrate in the cytosol to decrease and favors inactivation of the enzyme.)
Which one of the following statements concerning the biosynthesis of cholesterol is
CORRECT?
A. The rate-limiting step is the formation of 3-hydroxy-3-methylglutaryl-CoA (HMG-CoA)
by the enzyme HMG-CoA synthase.
B. Synthesis occurs in the cytosol of the cell.
C. All the carbon atoms in the cholesterol synthesized originate from acetyl-CoA.
D. Squalene is the first cyclic intermediate in the pathway.
E. The initial substrate is mevalonate.
Give this one a try later!
C
(Explanation: Cholesterol is synthesized in the endoplasmic reticulum from
acetyl CoA. The rate-limiting step is the formation of mevalonate from 3-
