| Date | November 2019 | Marks available | 3 | Reference code | 19N.3.hl.TZ0.21 |
| Level | HL | Paper | 3 | Time zone | TZ0 |
| Command term | Explain | Question number | 21 | Adapted from | N/A |
Question
Codeine, morphine and diamorphine (heroin) are derived from opium.
Explain why diamorphine has greater potency than morphine.
Experimental research on both animals and humans contributes to the development of pharmaceuticals.
State the meaning of the term therapeutic index in human studies.
Markscheme
Any three of:
morphine has «two» hydroxyl «groups» AND diamorphine has «two» ester/ethanoate/acetate «groups» ✔
NOTE: Accept “heroin” for “diamorphine”.
Accept formulas.
Accept “hydroxy” for “hydroxyl” but not “hydroxide”.
Accept “acyl” for “ester «groups»”.
morphine is more polar than diamorphine
OR
groups in morphine are replaced with less polar/non-polar groups in diamorphine ✔
NOTE: Do not accept just “diamorphine is non-polar” for M2.
morphine is «more» soluble in blood «plasma»
NOTE: Accept “water” for “blood”.
OR
diamorphine is «more» soluble in lipids
NOTE: Accept “fats” for “lipid”.
OR
diamorphine is more soluble in non-polar environment of CNS/central nervous system than morphine ✔
diamorphine crosses the blood–brain barrier/BBB «easily» ✔
toxic dose for 50% of population divided by «minimum» effective dose for 50 % of population ✔
NOTE: Accept “TD50/ED50”.
Reference to 50% required.
