review-examIII-2011

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Transcript review-examIII-2011

Review session for exam-III
Q1. Which of these is able to cross the inner
mitochondrial membrane?
A.
B.
C.
D.
E.
fatty acyl-CoA
malonyl-CoA
acetyl-CoA
fatty acyl-carnitine
none of the above can cross
Q2. The normal sequence of action of these
components of the hormonal hierarchy is:





adrenal cortex  hypothalamus  anterior pituitary
anterior pituitary  adrenal cortex  hypothalamus
anterior pituitary  hypothalamus  adrenal cortex
hypothalamus  adrenal cortex  anterior pituitary
hypothalamus  anterior pituitary  adrenal cortex

Q3. Describe five possible fates for
glucose 6-phosphate in the liver.
Q3 answer

(1) conversion to liver glycogen; (2)
dephosphorylation and release of
glucose into bloodstream; (3) oxidation
via the pentose phosphate pathway;
(4) oxidation via glycolysis and the
citric acid cycle; (5) oxidation to acetylCoA, which then serves as precursor
for synthesis of triacylglycerols,
phospholipids, and cholesterol.
Q4. What is leptin? How does it
function in the long-term
maintenance of body mass?
Q4 Answer
Leptin is a small polypeptide that is produced
in adipocytes and is carried by the blood to
the brain. It is produced when there are
adequate stores of lipid in the adipocytes
and interacts with a receptor in the
hypothalamus. This interaction produces a
cascade of effects that tend to suppress
appetite and increase energy expenditure.
Q5. Which of the following cannot be used as an
energy source by the brain?
a.
b.
c.
d.
glucose
ketone bodies
fatty acids
acetoacetate
Q6. . Which of the following is a major effect
of insulin binding to its receptor?

a. autophosphorylation of tyrosine
b. dephosphorylation of substrates
such as IRS-1
c. binding of phosphatidylinositol-3kinase to the receptor
Q7. What hormone(s) is (are) a signal of the
"fed state"?
a.
b.
c.
d.
Insulin
Glucagon
both insulin and glucagon
aldosteron
Q8. Which of the following is NOT true of
acetoacetate and β-hydroxybutyrate?
A.
B.
C.
D.
They can provide energy for brain cells.
They allosterically modify other enzymes.
They are produced from the acetyl CoA of
fats.
They cannot be used in liver.
Q9. During prolonged starvation, what is the
last cellular material to be utilized?
a.
b.
c.
d.
Glycogen
Fats
Proteins
Cholesterol
Q10. Which of these can be synthesized by
plants but not by humans?
A.
B.
C.
D.
E.
palmitate (18:0)
stearate (20:0)
linolenate [18:3(D9,12,15)]
Arachidonic acid
phosphatidylcholine
Q11. Type 2 Diabetes is a disease characterized by
overproduction of glucose by the liver and its underutilization
by other organs. Which of the following is NOT a cause of
diabetes?
a.inability to produce insulin
b.loss of ability to respond to insulin
when it is produced
c.the generation of enzymes in the
blood that rapidly degrade insulin
after release from the pancreas

Q12. What are plasma lipoproteins?
What is their general role in
mammalian metabolism?

Q13. The synthetic compound
mevinolinic acid, also called
lovastatin, is a potent competitive
inhibitor of HMG-CoA reducdase
(hydroxymethylglutaryl-CoA
reductase). Predict and explain the
effect of this drug on serum
cholesterol levels in humans.
Q14. The glycerol produced during the lipolysis of
triglycerides
A. is a waste product that is excreted from cells.
B. is stored within the cell for future synthesis of
tryglycerides.
C. can be used as either a source of energy or for
gluconeogenesis.

Q15. Write additional enzymes to
oxidize fatty acids that have double
bonds.
Q16. The degradation of an 18-carbon saturated
fatty acid would be expected to yield how many
NADH and FADH2 per fatty acid molecule?





A. 6
B. 10
C. 7
D. 8
E. 9
Q17. The NADPH used in the reductive
steps of fatty acid biosynthesis comes from
a.
b.
c.
one NADPH being generated per
citrate leaving the mitochondria.
the degradation of glucose via the
pentose phosphate pathway
exclusively
both a and b.
Q18. Ubiquitin is added to ………….
residues on proteins targeted for
degradation.
a.
b.
c.
d.
e.
Lysine
Asp
Gln
all of the above
none of the above
Q19. Cholesterol is synthesized from:
A.
B.
C.
D.
E.
acetyl-CoA.
choline.
lipoic acid.
malate.
oxalate.
Q 20. Which of these statements about the
regulation of cholesterol synthesis is not
true?
A.
B.
C.
D.
E.
Cholesterol acquired in the diet has essentially no
effect on the synthesis of cholesterol in the liver.
Failure to regulate cholesterol synthesis
predisposes humans to atherosclerosis.
High intracellular cholesterol stimulates formation
of cholesterol esters.
Insulin stimulates HMG-CoA reductase.
Some metabolite or derivative of cholesterol
inhibits HMG-CoA reductase.
Q21. The synthesis of fatty acids and their breakdown by b oxidation
occur by separate pathways. Compare the two paths by filling in the
blanks below. (Some blanks may require more than one answer.)
Activating group
Electron carrier coenzyme(s)
Basic units added or removed
Cellular location of process
Synthesis
b oxidation
—————————————————
_______________
___________
_______________
___________
_______________
____________
_______________
____________
Q21. Answer
Activating group
Electron carrier coenzyme(s)
Basic units added or removed
Cellular location of process
Synthesis
b oxidation
—————————————————
acyl carrier protein
CoA—SH
NADPH
NAD+
malonyl- and acetyl
acetylcytosol in animals
mitochondrial matrix
Q22. Which of the following metabolic pathways
and intracellular localization of the pathway are
correctly paired
a. b oxidation of fatty acids; mt. matrix
b. Citric acid cycle; cytoplasm
c. Fatty acid synthesis; cytoplasm
d. Glycolysis; mitochondrial matrix
e. Pentose phosphate pathway;
peroxisomes
Q23. Which of the following statements
about metabolism in the mammalian liver is
false?
A.
B.
C.
D.
E.
Most plasma lipoproteins are synthesized in the liver.
The enzymatic complement of liver tissue changes in
response to changes in the diet.
The liver synthesizes most of the urea produced in the body.
The presence of glucose 6-phosphatase makes liver uniquely
able to release glucose into the bloodstream.
Under certain conditions, most of the functions of the liver can
be performed by other organs.
Q24. The Cori cycle is:
A.
B.
C.
D.
E.
the conversion of lactate to pyruvate in skeletal muscle to
drive glycogen synthesis.
the interconversion between glycogen and glucose lphosphate.
the production of lactate from glucose in peripheral tissues
with the resynthesis of glucose from lactate in liver.
the synthesis of alanine from pyruvate in skeletal muscle and
the synthesis of pyruvate from alanine in liver.
the synthesis of urea in liver and degradation of urea to
carbon dioxide and ammonia by bacteria in the gut.
Q25. The largest energy store in a wellnourished human is:
A.
B.
C.
D.
E.
ATP in all tissues.
blood glucose.
liver glycogen.
muscle glycogen.
triacylglycerols in adipose tissue.
Q26. What distinguishes eicosanoids from other potent
biological signaling molecules such as
epinephrine?
Q26 answer
Eicosanoids are paracrine hormones: they generally do
not move long distances between their points of
release and their points of action.
Q27. In animals, the carbon backbone of glucose _____ be
metabolically converted and stoichiometrically utilized for synthesis of
fatty acids; in animals, the carbon backbone of fatty acids _____ be
metabolically converted and stoichiometrically utilized for synthesis of
glucose.
a.
b.
c.
d.
e.
Can; can
Can; cannot
Can only; can only
Cannot; can
Cannot; cannot
Q28. Which of the following intermediate in
cholesterol biosynthesis is the substrate for the
enzyme at the key regulatory step of the pathway
a.
b.
c.
d.
e.
Dimethylallyl pyrophosphate
3-hydroxy-3-methylglutaryl-CoA
3-isopentyl pyrophosphate
Malonyl-CoA
Mevalonate
Q29. Which of the following best describes, in order, the
complete series of catalyzed reactions that occurs as a
molecule of acyl-CoA is shortened by one two-carbon unit
during fatty acid degradation
a.
b.
c.
d.
e.
Hydration; oxidation; thiolysis
Oxidation; hydration; oxidation; thiolysis
Oxidation; hydration; reduction; thiolysis
Oxidation; hydration; thiolysis
Reduction; hydration; oxidation; thiolysis
Q29 Answer
a.
b.
c.
d.
e.
Hydration; oxidation; thiolysis
Oxidation; hydration; oxidation; thiolysis
Oxidation; hydration; reduction; thiolysis
Oxidation; hydration; thiolysis
Reduction; hydration; oxidation; thiolysis
Q30. During b oxidation, the carbon
backbone of fatty acids is converted into
which of the following
a.
b.
c.
d.
e.
Carbon dioxide
Pyruvate
Acetyl groups
Malonyl groups
Succinyl groups
Q30 answer
a.
b.
c.
d.
e.
Carbon dioxide
Pyruvate
Acetyl groups
Malonyl groups
Succinyl groups