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TitleMed Board Biochem MCQ-Answer Key
TagsAdenosine Triphosphate Glycolysis Pyruvic Acid Enzyme Inhibitor Antibody
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Page 8

Physician Licensure Examination
June 3, 2008; 8:00 – 12:00

distress syndrome)?
A. phosphatidylcholine.
B. phosphatidylinositol.
C. phosphatidic acid.
D. cardiolipin.
E. sphingomyelin.

51. Increased excretion of urobilinogen in the urine is most commonly the result of
A. hemolysis.
B. erythropoetic porphyria.
C. liver disease such as viral hepatitis.
D. iron deficiency.
E. bile duct obstruction.

52. Which of the following statements about the pentose phosphate pathway is INCORRECT?
A. Pentoses can be formed both oxidatively and non-oxidatively.
B. This pathway is important to fatty acid synthesis because it produces reducing equivalents.
C. Fructose 6-phosphate can be used to make ribose 5-phosphate.
D. Glyceraldehyde 3-phosphate can be used to make ribose 5-phosphate.
E. NADH is formed by the action of glucose 6-phosphate dehydrogenase.

53. The "methyl trap" hypothesis states that in the absence of vitamin B12, there is a block in the
further metabolism of
A. N5-methyl tetrahydrofolate (THF) monoglutamate.
B. N5,10-methylene THF.
C. N10-formyl THF.
D. N5,10-methenyl THF.
E. dihydrofolate.

54. Actin is released from its interaction with myosin by the addition of:

B. magnesium ions
C. inorganic phosphate

E. calcium ions

55. As regards receptors coupled to Gs (stimulatory G protein) and cAMP, which of the
following is FALSE?
A. Binding of a hormone to its receptor activates an enzyme which catalyzes
the displacement of GDP with GTP on the alpha Gs subunit.
B. The Gs alpha subunit dissociates from the beta/gamma subunits and activates adenylate
C. Adenylate cyclase catalyzes the conversion of ATP to cAMP.
D. cAMP activates cAMP dependent protein kinase by binding to the regulatory subunits which
causes dissociation of the regulatory subunits from the catalytic subunits.
E. The catalytic subunit of cAMP dependent protein kinase phosphorylates proteins on serine.

56. The only apoprotein in LDL is:

A. Apo A
B. Apo B-100
C. Apo CII

D. Apo D
E. Apo B-48

57. For transport across the inner mitochondrial membrane, long chain fatty acids are attached to:

A. coenzyme A.
B. acyl transacylase.
C. phosphatidylethanolamine.

D. acyl transferase.
E. carnitine.

58. The activity of lipoprotein lipase is stimulated by:
B. APO B-48
E. APO B-100

59. A major contributing factor to cataract formation in diabetes may be the accumulation of
sorbitol in the lens. For that to occur, glucose has to interact with:
A. hexokinase and phosphoglucose isomerase
B. fructose dehydrogenase
C. aldose reductase
D. hexokinase and glucose 6-phosphate dehydrogenase
E. glucose oxidase

60. The sphingolipidoses are a group of diseases involving defective breakdown of ceramides.
Which one of the following is characteristic for a ceramide?
A. an N-linked fatty acid residue
B. a residue of glycerol.
C. a phosphorylcholine residue
D. three fatty acid residues
E. contains a thiol

61. The rate-limiting step in the conversion of cholesterol to bile acids is
A. side chain oxidation.
B. 12-alpha-hydroxylation.
C. 7-alpha-hydroxylation.


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