| Date | November 2010 | Marks available | 3 | Reference code | 10N.3.hl.TZ0.D3 |
| Level | HL | Paper | 3 | Time zone | TZ0 |
| Command term | Identify | Question number | D3 | Adapted from | N/A |
Question
Three factors which can influence the mechanism of the action of a drug include geometrical isomerism, polarity and ring strain.
For each of the following drugs, identify which one of these factors is involved.
Increased potency of diamorphine compared to morphine:
Penicillin:
Explain the action of penicillin with reference to your answer in part (a).
Markscheme
Increased potency of diamorphine compared to morphine:
polarity / polar hydroxyl groups in morphine replaced by non-polar ester groups in diamorphine;
Penicillin:
ring strain;
ring opens (to allow penicillin to bond to enzyme);
which synthesizes bacterial cell walls and so blocks action / prevent cell wall/membrane formation;
Examiners report
Most candidates had no problem with (a).
in (b), although most candidates knew that penicillin interferes with cell wall synthesis, most did not know the actual mechanism i.e. the fact that the ring opens to allow the penicillin to bond to the enzyme.
