| Date | November 2016 | Marks available | 1 | Reference code | 16N.3.sl.TZ0.19 |
| Level | SL | Paper | 3 | Time zone | TZ0 |
| Command term | Formulate | Question number | 19 | Adapted from | N/A |
Question
Excess stomach acid leads to medical conditions that affect many people worldwide. These conditions can be treated with several types of medical drugs.
Ranitidine (Zantac) is a drug that inhibits stomach acid production. Outline why the development of this drug was based on a detailed knowledge of the structure of histamine, shown below.
Two other drugs, omeprazole (Prilosec) and esomeprazole (Nexium), directly prevent the release of acid into the stomach. Identify the site of action in the body.
A different approach to treating excess stomach acid is to neutralize it with antacids. Formulate an equation that shows the action of an antacid that can neutralize three moles of hydrogen ions, H+, per mole of antacid.
Markscheme
«ranitidine» blocks/inhibits histamine binding to «H2» receptor
OR
ranitidine binds to same «H2» receptors «as histamine»
OR
competes with histamine for binding
proton pump
OR
H+ /K+ ATPase enzyme
Accept “«secretary surface of» parietal cells”.
Do not accept “stomach/stomach wall”.
Al(OH)3(s) + 3H+ (aq) → Al3+ (aq) + 3H2O (l)
OR
Al(OH)3(s) + 3HCl (aq) → AlCl3 (aq) + 3H2O (l)
