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Question 1

To what extent are the three nitrogens of histamine ionised at blood pH?

a) All three nitrogens are fully ionised.

b) All three nitrogens are not ionised at all.

c) The side chain nitrogen is fully ionised and the heterocyclic nitrogens are not ionised.

d) The side chain nitrogen and one of the heterocyclic nitrogens are fully ionised.

Question 2

Three binding regions were proposed to be present in the binding site of the H₂ receptor. Which of the following statements is incorrect?

a) There is a binding region for the imidazole ring of histamine analogues which is common for agonists and antagonists.

b) There is a binding region which interacts ionically with the α-nitrogen of histamine and results in agonist activity.

c) There is a binding region further away from the imidazole ring that produces an antagonist effect if occupied.

d) The α-nitrogen of histamine can only bind to the agonist binding region while the guanyl group of Nα-guanylhistamine can only bind to the antagonist binding region.

Question 3

The following structures show some of the important molecules leading to the discovery of burimamide (B).

What strategy was used in developing burimamide from SK&F 91581?

a) extension

b) chain extension

c) substituent variation

d) isosteric replacement

Question 4

The following structures show some of the important molecules leading to the discovery of burimamide (B).

Which of the following statements concerning burimamide is untrue?

a) It established the existence of H₂-receptors.

b) It was a good antagonist at H₂ receptors with only weak partial agonist activity.

c) It inhibited gastric acid release from parietal cells.

d) It indicated that binding to the antagonist binding region involved hydrogen bonding and not ionic bonding.

Question 5

The following diagram shows development of H₂-antagonists from burimamide (structure B).

A sulfur atom was inserted into the side chain of structure C. What effect did this change have?

a) It introduced an extra binding interaction.

b) It stabilised the molecule.

c) It increased the percentage population of the active heterocyclic tautomer.

d) It prevented ionisation of the terminal functional group.

Question 6

The following diagram shows development of H₂-antagonists from burimamide (structure B).

What was the rationale for the introduction of the coloured methyl group?

a) To block metabolism at that region of the heterocyclic ring.

b) To introduce a group which would be metabolised in a predictable fashion.

c) To introduce an electron withdrawing group on the heterocyclic ring to reduce the chance of ionisation.

d) To introduce an electron donating group on the heterocyclic ring to favour the active tautomer.

Question 7

The following diagram shows development of H₂-antagonists from burimamide (structure B).

Why was the thiourea functional group in structure D changed to a guanidine group in structure E?

a) To introduce a basic group which could ionise and allow ionic interactions with the binding region.

b) To replace an unnatural functional group with a naturally occurring group in order to reduce side effects.

c) To increase the number of hydrogen bond donors present to acquire extra binding interactions.

d) To change the geometry and stereochemistry of the functional group such that it fitted the binding region more closely.

Question 8

The following diagram shows development of H₂-antagonists from burimamide (structure B).

Why was the cyanide group introduced into structure F (cimetidine)?

a) It is an electron donating group and increases the basicity of the functional group such that it protonates and becomes ionised.

b) It is an electron withdrawing group and increases the basicity of the functional group such that it protonates and becomes ionised.

c) It is an electron donating group and decreases the basicity of the functional group such that it does not become protonated and remains un-ionised.

d) It is an electron withdrawing group and decreases the basicity of the functional group such that it does not become protonated and remains un-ionised.

Question 9

Two regions of cimetidine are susceptible to metabolism. Which regions?

a) A and B.

b) A and C.

c) B and D.

d) A and D.

Question 10

The following diagram shows various conformations for the cyanoguanidine group of cimetidine.

Two of these conformations were found to be disfavoured. Which ones and what was the implication of this for receptor binding?

a) EZ and ZE. It proved the chelation theory of hydrogen bonding.

b) EZ and ZZ. It established that there was only one hydrogen bonding interaction with the receptor in this region.

c) EE and ZZ. It established that there were two hydrogen bonding interactions to different groups within the same binding region.

d) EE and ZE. No conclusions could be drawn.

Question 11

Once activated, the proton pump inhibitors bind to exposed amino acids in the proton pump. Which amino acid is involved?

a) serine

b) cysteine

c) lysine

d) histidine

Question 12

The following mechanism shows how proton pump inhibitors are activated. Which arrow is incorrect?

a) A

b) B

c) C

d) D

Question 13

Omeprazole is an important proton pump inhibitor.

Which region is prone to metabolism?

a) A

b) B

c) C

d) D

Question 14

Which microorganism has been associated with the appearance of ulcers?

a) Eschericia coli

b) Staphylococcus aureus

c) Enterococcus faecalis

d) Helicobacter pylori

Question 15

What bacterial enzyme aids the survival of Helicobacter pylori in the stomach?

a) carbonic anhydrase

b) β-lactamase

c) urease

d) transpeptidase

Oxford University Press, Online Resource Centre, Chapter 25.

Chapter 25

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