757 - 765

Question 1

757 Regulation of de novo AMP synthesis involves:
Select one or more:

a. allosteric activation by GMP
b. allosteric inhibition by AMP
c. availability of PRPP

Answer 1

b. allosteric inhibition by AMP
c. availability of PRPP

Question 2

Select the correct statements regarding the synthesis of prostaglandins and thromboxanes!

Select one or more:
a. Arachidonic acid is an essential fatty acid, frequently found in membrane phospholipids
b. Arachidonic acid is released from membrane phospholipids by phospholipase A2
c. PGH-synthase is a homodimer containing two different types of catalytic sites
d. Arachidonic acid is converted to PGG2 by a peroxidase
e. Platelets synthesize exclusively PGI2 from arachidonic acid

Answer 2

b. Arachidonic acid is released from membrane phospholipids by phospholipase A2
c. PGH-synthase is a homodimer containing two different types of catalytic sites

Question 3

Select the correct statements regarding the biological effects of prostaglandins and thromboxanes!

Select one or more:
a. TXA2 promotes platelet aggregation
b. PGE2 promotes platelet aggregation
c. PGE2 protects gastric mucosa cells from the erosive effects of gastric juice
d. PGI2 inhibits platelet aggregation
e. PGE2 and PGF2a play a role in the regulation of uterus contractility

Answer 3

a. TXA2 promotes platelet aggregation
c. PGE2 protects gastric mucosa cells from the erosive effects of gastric juice
d. PGI2 inhibits platelet aggregation
e. PGE2 and PGF2a play a role in the regulation of uterus contractility

Question 4

How do the non-steroid anti-inflammatory drugs (NSAIDs) interfere with the synthesis of eicosanoids?

Select one or more:
a. Aspirin is a competitive inhibitor of the cyclooxygenase, COX-1 isoenzyme
b. The cyclooxygenase, COX-1 isoenzyme is completely blocked after acetylation of a Ser residue in its substrate-binding pocket
c. Aspirin prevents stroke in the elderly because it irreversibly acetylates the thromboxane synthase enzyme of platelets
d. NSAIDs decrease the inflammatory reactions by reversibly blocking the conversion of LTA4 to LTB4
e. The selective blockage of the cyclooxygenase, COX-2 isoenzyme could be a good strategy for pain relief without the side effect of gastric bleeding

Answer 4

b. The cyclooxygenase, COX-1 isoenzyme is completely blocked after acetylation of a Ser residue in its substrate-binding pocket
e. The selective blockage of the cyclooxygenase, COX-2 isoenzyme could be a good strategy for pain relief without the side effect of gastric bleeding

Question 5

Orotic aciduria might be caused by the deficiency of:

Select one or more:
a. hypoxanthine-guanosine phosphoribosyl transferase
b. UMP synthase
c. adenosine deaminase
d. Ornithine transcarbamoylase

Answer 5

b. UMP synthase
d. Ornithine transcarbamoylase

Question 6

762 What are the correct statements regarding leukotrienes?

Select one or more:
a. The cysteinyl leukotrienes include LTC4, LTD4 and LTE4
b. LTA4 and LTB4 together form the ``slow-reacting substance of anaphylaxis’’ that plays a major role in the pathogenesis of asthma bronchiale
c. Montelukast (Singulair) and zafirlukast (Accolate) block the receptor for cysteinyl leukotrienes
d. Leukotrienes are named after their capability to absorbe white light
e. LTB4 is a chemotactic factor for neutrophil granulocytes

Answer 6

a. The cysteinyl leukotrienes include LTC4, LTD4 and LTE4
c. Montelukast (Singulair) and zafirlukast (Accolate) block the receptor for cysteinyl leukotrienes
e. LTB4 is a chemotactic factor for neutrophil granulocytes

Question 7

Which of the following conditions out of A-D can cause gout?

Select one or more:
a. mutation at the allosteric site of PRPP synthase
b. glucose-6-phosphatase deficiency
c. hypoxanthine-guanine phosphoribosyl transferase deficiency
d. fructose intolerance

Answer 7

a. mutation at the allosteric site of PRPP synthase
b. glucose-6-phosphatase deficiency
c. hypoxanthine-guanine phosphoribosyl transferase deficiency
d. fructose intolerance

Question 8

Administration of allopurinol to a patient with gout, who has a normal HG-PRT level, would lead to all of the following EXCEPT:

Select one:
a. Decreased de novo synthesis of IMP.
b. Decreased urate in the urine.
c. An increase of hypoxanthine in the blood.
d. Increased levels of PRPP .
e. Increased xanthine in the blood.

Answer 8

d. Increased levels of PRPP .

(Explain:
HG-PRT: Hypoxanthine-guanine phosphoribosyltransferase
Allopurino affect xanthine oxidase?)