MC test: pH regulation of the stomach

Multiple choice test on D.4 pH regulation of the stomach

Use the following 'quiz' to test your knowledge and understanding of this sub-topic. As this relates to a sub-topic on the options you may need access to the IB data booklet.

If you get an answer wrong, read through the explanation carefully to learn from your mistakes.

The relative molar masses of four common antacids are:

Antacid Mr
magnesium hydroxide 58.34
aluminium hydroxide 78.01
calcium carbonate 100.09
sodium carbonate 105.99

Weight for weight, which one can neutralise the most acid?

58.34 g of Mg(OH)2 neutralises 2.00 moles of a monoprotic acid. 58.34 g of Al(OH)3 is equal to 58.34/78.01 = 0.748 mol of Al(OH)3. Since each mol of Al(OH)3 neutralises 3 mol of a monoprotic acid 58.34 g of Al(OH)3 will neutralise 3 x 0.748 = 2.44 mol of acid.

 

Which can function as an antacid?

Iron(II) sulfate is not a base so cannot neutralise excess stomach acid. Lead(II) oxide and copper(II) carbonate are bases but the metal ions are poisonous so cannot be used to combat excess stomach acid.

 

Which can form an acidic buffer solution?

I. an excess of a weak acid mixed with a strong base in solution

II. an equimolar aqueous mixture of a weak acid and the potassium salt of that acid

III. a weak base mixed with an excess of a strong acid

Once all the strong base has reacted in I the resulting mixture will contain the excess of the weak acid together with its conjugate base. Similarly in II the mixture contains a weak acid together with its conjugate base. In III once all the weak base has reacted the resulting solution contains a strong acid so is not a buffer solution.

 

What is the pH of a 0.100 mol dm−3 solution of a monoprotic acid with a pKa value of 4.76 which also contains a 0.100 mol dm−3 solution of the sodium salt of the acid?

Since [HA] = [A−], pH = pKa

 

Ranitidine is an H2 receptor antagonist. What does the H stand for in H2?

Ranitidine suppresses the production of stomach acid by blocking the action of histamine on the H2 receptors of parietal cells in the lining of the stomach.

 

Which properties may be possessed by active metabolites?

I. They may be more effective in their action as a drug than their original form before being metabolised by the body.

II. They may be less effective in their action as a drug than their original form before before being metabolised by the body.

III. They may be as effective in their action as a drug as their original form before before being metabolised by the body.

The important fact about active metabolites is that they are still active as a drug, however they may be more or less active than their original form or possess the same activity.

 

Which cells in the stomach are responsible for the production of stomach acid (gastric juice)?

The parietal cells (also sometimes known as oxyntic or delomorphous cells) secrete hydrochloric acid in the stomach.

 

Which describes  H+/K+ ATPase?

H+/K+ ATPase is an enzyme commonly known as the 'proton pump' which enables parietal cells to make hydrochloric acid.

 

Omeprazole and esomeprazole can be used to reduce excess stomach acid. Which describes their mode of action?

Both are PPIs (proton pump inhibitors) which work by interacting with a cysteine residue on the proton pump thus blocking the action of the enzyme.

 

Which antacids may lead to belching as a side-effect?

I. sodium hydrogen carbonate

II. 'Milk of magnesia' (a mixture of magnesium oxide and magnesium hydroxide).

III. sodium carbonate

Belching is caused by the release of carbon dioxide formed during the neutralisation of excess stomach acid by carbonates or hydrogen carbonates.

 

Total Score:
All materials on this website are for the exclusive use of teachers and students at subscribing schools for the period of their subscription. Any unauthorised copying or posting of materials on other websites is an infringement of our copyright and could result in your account being blocked and legal action being taken against you.