Question 18M.3.sl.TZ1.13
| Date | May 2018 | Marks available | [Maximum mark: 12] | Reference code | 18M.3.sl.TZ1.13 |
| Level | sl | Paper | 3 | Time zone | TZ1 |
| Command term | Compare and contrast, Describe, Outline, State, Suggest | Question number | 13 | Adapted from | N/A |
Many drugs, including aspirin, penicillin, codeine and taxol, have been modified from compounds that occur naturally.
Aspirin is often taken to reduce pain, swelling or fever. State one other use of aspirin.
[1]
Any one of:
anticoagulant
lower risk of heart attack/strokes
prevent recurrence of heart attack/stroke
prevents cancer of colon/oesophagus/stomach
Accept “prevents/reduces blood clots” OR “blood thinner”.
[1 mark]
State what is meant by the bioavailability of a drug.
[1]
fraction/proportion/percentage «of administered dosage» that reaches target «part of human body»
OR
fraction/ proportion/percentage «of administered dosage» that reaches blood «plasma»/systemic circulation
Accept “the ability of the drug to be absorbed by the body” OR “the extent to which the drug is absorbed by the body”.
Do not accept “the amount/quantity of the drug absorbed”.
[1 mark]
Outline how the bioavailability of aspirin may be increased.
[1]
«intravenous» injection/IV
Accept “parenterally”.
Accept “react with alkali/NaOH” OR “convert to ionic form/salt”.
[1 mark]
Compare and contrast the IR spectrum of aspirin with that of salicylic acid, using section 26 of the data booklet.
[2]
One absorption found in both spectra:
Any one of:
1050–1410 cm–1 «C–O in alcohols, esters, ethers»
1700–1750 cm–1 «C=O in carboxylic acids, esters»
2500–3000 cm–1 «O–H in carboxylic acids»
2850–3090 cm–1 «C–H in alkanes, alkenes, arenes»
One absorption found in only one of the spectra:
3200–3600 cm–1 «O–H in alcohols, phenols»
Award [1 max] if candidate states bonds (C=O in both, O–H in salicylic acid only) but doesn’t quote wavelength ranges.
Accept a second/additional absorption at 1700–1750 cm–1 from the C=O in ester.
[2 marks]
Describe how penicillin combats bacterial infections.
[2]
Any two of:
ring is «sterically» strained
OR
ring breaks up/opens/reacts «easily»
OR
amide/amido group «in ring» is «highly» reactive
«irreversibly» binds/bonds to enzyme/transpeptidase
OR
inhibits enzyme/transpeptidase «in bacteria» that produces cell walls
OR
prevents cross-linking of bacterial cell walls
cells absorb water AND burst
OR
cells cannot reproduce
Award [1 max] for “interferes with cell wall production”.
Do not accept “cell membrane” instead of “cell wall”.
[2 marks]
Outline two consequences of prescribing antibiotics such as penicillin unnecessarily.
[2]
Any two of:
leads to «bacterial» resistance/proportion of resistant bacteria increases
OR
leads to penicillinase-producing bacteria
damage to/contamination of bodies of water/ecosystems
destroys useful/beneficial bacteria
destroyed bacteria replaced by more harmful bacteria
Accept “endocrine disruptor”.
Do not accept “increased cost of developing antibiotics”.
[2 marks]
State how penicillins may be modified to increase their effectiveness.
[1]
modify side chain
[1 mark]
Morphine and codeine are strong analgesics. Outline how strong analgesics function.
[1]
temporarily bind to/block/interfere with receptor sites in brain
OR
prevent transmission of pain impulses within CNS/central nervous system
[1 mark]
Suggest one reason why codeine is more widely used than morphine as an analgesic.
[1]
codeine has a wider therapeutic window
Accept “codeine has lower activity” OR “codeine has lower risk of overdose” OR “codeine is less potent” OR “codeine has less side-effects”.
Do not accept “lower abuse potential for codeine” OR “less addictive «than morphine»” OR “codeine has a lower bioavailability” OR “available without prescription” OR “cheaper”.
[1 mark]