Question 20N.3.sl.TZ0.14
| Date | November 2020 | Marks available | [Maximum mark: 10] | Reference code | 20N.3.sl.TZ0.14 |
| Level | sl | Paper | 3 | Time zone | TZ0 |
| Command term | Annotate, Explain, Name, State, State and explain | Question number | 14 | Adapted from | N/A |
Consider the structures of medicinal molecules in section 37 of the data booklet.
Name two functional groups that both zanamivir and oseltamivir contain.
[2]
Any two:
«secondary» carboxamide/amido ✔
ether ✔
carbonyl ✔
Accept amide
Accept amino/amine.
Accept alkenyl/alkene.
Do not accept formula.
Most students scored both marks here. Some students with incorrect answers gave carboxylic acid/carboxyl, benzene/arene, and ester.
Explain how zanamivir works as a preventative agent against flu viruses.
[2]
«drug» blocks/inhibits «viral» enzyme/neuraminidase/ «activity» ✔
prevents virus from leaving/escaping host cells «thus cannot infect other cells» ✔
Do not accept other anti-viral methods (as question is specific to Zanamivir).
Even when a relevant number of students obtained at least one mark, the quality of the answers was in general low and many evidenced very shallow understanding just repeating information
Circle the side-chain in penicillin on the structure below.
[1]
✔
Accept a circle that does not surround the amido group.
Do not accept a circle that only surrounds the phenol group.
Many students scored here but a relevant percentage didn't include the amide group. Quite a few students did not know where the side chain is and circled other parts of the molecule.
Explain, with reference to the action of penicillin, why new penicillins with different side-chains need to be produced.
[2]
bacterial resistance «to older penicillins/antibiotics» ✔
prevent penicillinase/beta-lactamase/enzyme in bacterium to deactivate/open penicillin/beta-lactam ring ✔
Accept “antibiotic resistant bacteria” but not “antibiotic resistance” for M1.
Accept “reduce allergic reactions from from penicillin” for M2.
Award [1 max] for “increased efficiency” OR “increased stability in GIT”.
Do not accept “bacteria develop tolerance”.
Many good answers for M1 but only stronger students managed to score the second one. The answers evidenced again shallow understanding that may result from independent learning. Many students gave answers related to how penicillin causes bacteria to burst which is not related to this question. Once again it shows students perhaps memorizing answers without a true understanding of concepts.
State and explain the relative solubility of codeine in water compared to morphine and diamorphine.
[2]
codeine less soluble «in water» than morphine AND more soluble than diamorphine
OR
morphine > codeine > diamorphine «in terms of solubility in water» ✔
more/stronger/greater hydrogen/H bonding «due to more hydroxyl groups leads to greater solubility» ✔
M1 was correctly presented but most students focused on the polarity of the molecules and presented long arguments where intermolecular forces were ignored. The concept of water solubility and hydrogen bonding was largely ignored.
State the natural source from which codeine, morphine and diamorphine are obtained.
[1]
opium poppy/plants/seeds ✔
Accept “poppy” OR “opioid”.
Mostly well answered. Student who missed this question were clearly guessing with other natural products presented with the Option D material.