766 - 798 2nd sem

Question 1

What is not the significance/purpose of drug metabolism?

Select one:
a. Phase 1 metabolism renders compounds more reactive.
b. Phase 1 metabolism produces groups that can be conjugated.
c. Metabolism of xenobiotics produces water-soluble compounds.
d. Products of drug metabolism can be excreted by bile.
e. Hydrophobic products of drug metabolism persist in adipose tissue.

Answer 1

e. Hydrophobic products of drug metabolism persist in adipose tissue.

Question 2

What is not the characteristic of the so called prodrug?

Select one:
a. Inactive.
b. It becomes active after special chemical reaction.
c. Activation of prodrug occurs in the pharmaceutical factory. d. One category is called procarcinogen.
e. Prodrugs are more hydrophobic than drugs.

Answer 2

c. Activation of prodrug occurs in the pharmaceutical factory.

Question 3

What can be the substrate of cytochrome P450 enzymes?
1. medicines
2. steroid hormones
3. pollutants
4. vitamin D
5. naturally occurring compounds in plant foods

A: 1,2,3
B: 4,5
C: 1,3,5
D: 2,4
E: 1,2,3,4,5

Answer 3

E: 1,2,3,4,5

Question 4

What can be the other name of cytochrome P450 enzyme system?

1. hydroxylase
2. dioxygenase
3. monooxygenase
4. cytochrome oxidase
5. mixed-function oxygenase

A: 1,2,3
B: 4,5
C: 1,3,5
D: 2,4
E: 1,2,3,4,5

Answer 4

C: 1,3,5

1. hydroxylase
2. monooxygenase
3. mixed-function oxygenase

Question 5

Cytochrome P450 enzymes are included in the same family if they exhibit … % or more amino acid sequence identity.

Select one:
a. 80
b. 65
c. 55
d. 40
e. 30

Answer 5

d. 40

Question 6

Cytochrome P450 enzymes are included in the same subfamily if they exhibit … % or more amino acid sequence identity.

Select one:
a. 80
b. 65
c. 55
d. 40
e. 30

Answer 6

c. 55

Question 7

Which pair of name AND function is false?

Select one:
a. CYP4 – arachidonic acid and fatty acid metabolism
b. CYP7 – hydroxylase in bile acid synthesis
c. CYP11 – hydroxylase in corticosteroid synthesis
d. CYP19 – aromatase
e. CYP101 – cholesterol degradation

Answer 7

e. CYP101 – cholesterol degradation

Question 8

What can be the location of cytochrome P450 enzymes in human cells?

1. Cytosol
2. ER membrane
3. ER lumen
4. mitochondrium membrane
5. mitochondrium matrix

A:1,2,3
B: 4,5
C: 1,3,5
D: 2,4
E: 1,2,3,4,5

Answer 8

D: 2,4

Question 9

The amount of cytochrome P450 enzymes can be increased by
1. increased transc
ription of mRNA
2. increased stabilization of mRNA
3. increased stabilization of enzyme protein
4. increased translation of enzyme protein
5. by no means, just the activity can be increased

A: 1,2,3,4
B: 5
C: 1,3
D: 2,4
E: 1

Answer 9

1/ increased transcription of mRNA
2/ increased stabilization of mRNA
3/ increased stabilization of enzyme protein increased
4/ translation of enzyme protein
(A)

Question 10

Which organ/tissue contains the biggest amount of cytochrome P450 enzymes?

Select one:
a. brain
b. heart
c. liver
d. kidney
e. adipose tissue

Answer 10

c. liver

Question 11

What are the components of the microsomal cytochrome P450 enzyme system?

1. NADPH
2. FAD
3. cytochrome P450 reductase
4. a hemoprotein
5. adrenodoxin

A: 1,2,3,4
B: 5
C: 1,3
D: 2,4
E: 1

Answer 11

A: 1,2,3,4

Question 12

What is true about glucuronidation?
1. One substrate is UDP-glucuronate.
2. The enzyme is a glucuronosyltransferase.
3. The location is cytosol or ER.
4. It is the most frequent conjugation reaction.
5. The glucuronic acid is attached to O, N, S atom of the substrate.

A:1,2,3
B: 1,2,3,4,5
C: 1,3,5
D: 2,4
E: 4,5

Answer 12

B: 1,2,3,4,5

Question 13

What is false about glucuronidation?

Select one:
a. Bilirubin is excreted as glucuronide conjugate.
b. It renders the products of phase 1 reaction more water-soluble.
c. Lot of medicines can be glucuronidated.
d. Glucuronide conjugates are excreted out of the cells, out of the body.
e. Exclusively OH group can be conjugated by glucuronate.

Answer 13

e. Exclusively OH group can be conjugated by glucuronate.

Question 14

What is false about sulfatation?

Select one:
a. The sulfate donor is PAPS.
b. The enzyme is sulfotransferase.
c. Steroids are inactivated by this reaction.
d. It participates in the synthesis of glucosaminoglycans.
e. The reaction takes place in all cell organelles.

Answer 14

e. The reaction takes place in all cell organelles.

Question 15

What is not valid for conjugation with GSH (glutathione)?

Select one:
a. It is an electrophilic reaction.
b. One substrate is a tripeptide.
c. The enzyme is glutathione S-transferase.
d. Glutamate carboxyl group is attached to the substrate.
e. Conjugates are excreted by urine or bile/gut.

Answer 15

d. Glutamate carboxyl group is attached to the substrate.

Question 16

What is true about the conjugation with glutathione by glutathione S- transferase?

1. GST enzyme is found in ER (microsome), mitochondria and peroxisome.
2. GST enzyme binds a number of ligands that are not substrates, and can transport them.
3. Liver has especially high activity of GSH conjugation.
4. Even the high amount of GSH can be depleted within minutes on exposure to xenobiotics.
5. The activity of GST is upregulated in many tumors, leading to resistance to chemotherapy.

A: 1,2,3
B: 1,2,3,4,5
C: 1,3,5
D: 2,4
E: 4,5

Answer 16

All of them (B)

Question 17

Which statements are true for the cyclooxygenase enzymes?

Select one or more:
a. the enzyme is also called PGH-synthase
b. cyclooxygenases belong to the family of cytochrome P 450 isoenzymes
c. arachidonate is a substrate for the enzyme
d. aspirine inhibits cyclooxygenase activity
e. in addition to the cyclooxygenase activity, the enzyme also exhibits epoxidase activity

Answer 17

a. the enzyme is also called PGH-synthase
c. arachidonate is a substrate for the enzyme
d. aspirine inhibits cyclooxygenase activity

Question 18

How many cyclooxygenase isoenzymes are known?

Select one:
a. 4
b. 3
c. 2
d. there are no isoforms of this enzyme
e. there are no isoforms but the enzyme can exist in phosphorylated form

Answer 18

c. 2

Question 19

Which of the following statements is not true?

Select one:
a. The active form of cyclooxygenase is monomeric
b. a serine residue of cyclooxygenase can be acetylated by aspirin
c. aspirin blocks cyclooxygenase-1 by irreversible covalent modification
d. Cyclooxygenase is a membrane-bound homodimeric enzyme
e. each cyclooxygenase monomer contains two different active centers

Answer 19

a. The active form of cyclooxygenase is monomeric

Question 20

Which statements are valid for arachidonic acid?

Select one or more:
a. It can be released from phospholipids
b. Phospholipase C catalyzes its release from the plasma membrane
c. Prostaglandins are produced from arachidonic acid
d. Cyclooxygenase catalyzes the synthesis of leukotrienes

Answer 20

a. It can be released from phospholipids
c. Prostaglandins are produced from arachidonic acid

Question 21

Prerequisites for thromboxane synthesis are:

Select one or more:
a. availability of phospholipid containing arachidonate for phospholipase A2
b. active lipoxygenase
c. functional cyclooxygenase
d. corticosteroids do not inhibit cyclooxygenase

Answer 21

a. availability of phospholipid containing arachidonate for phospholipase A2
c. functional cyclooxygenase
d. corticosteroids do not inhibit cyclooxygenase

Question 22

Which of these can be synthesized by plants but not by humans?

Select one:
a. linoleate [18:2(D9,12)]
b. palmitate (16:0)
c. phosphatidylcholine
d. pyruvate
e. stearate (18:0)

Answer 22

a. linoleate [18:2(D9,12)]

Question 23

Which of these statements about eicosanoid synthesis is true?

Select one:
a. An early step in the path to thromboxanes is blocked by aspirin
b. Aspirin acts by blocking the synthesis of arachidonate.
c. Plants can synthesize leukotrienes, but humans cannot.
d. Thromboxanes are produced from arachidonate via the “lipoxygenase” path.

Answer 23

d. Thromboxanes are produced from arachidonate via the “lipoxygenase” path.