IB DP Chemistry D.5 Anti-viral medications HL Paper 3

Question

Explain two different ways antiviral medications work.

Answer/Explanation

Answer:

Any two of:

alters «viral» enzyme AND prevent virus from entering the cell .
alter the cell DNA AND virus cannot multiply
block «cell» enzyme activity AND prevent virus multiplication
alters «viral» enzyme AND prevents release of «new» viral particles «from the
cell»

Question

Many illnesses are caused by bacteria and viruses.

(a) Explain two ways antiviral medications prevent the replication of viruses.

(b) Bacterial infections are treated using antibiotics such as penicillin. Suggest how penicillin can be modified and the reasons for the modification.

Answer/Explanation

Answer:

(a) Any two of:
«bind to receptors to» prevent virus entering cell
alter genetic material of cell/cytoplasm «to prevent replication»
block enzyme activity in cell «to prevent replication»
prevent virus leaving cell «by inhibiting viral enzyme/neuraminidase»

(b) side chain modified
overcome antibiotic resistance/ penicillinase ineffective 

Question

Consider the structures of medicinal molecules in section 37 of the data booklet.
a. Explain how zanamivir works as a preventative agent against flu viruses.
b(i)Circle the side-chain in penicillin on the structure below.

b(iiExplain, with reference to the action of penicillin, why new penicillins with different side-chains need to be produced.
c(i)State and explain the relative solubility of codeine in water compared to morphine and diamorphine.
c(ii)State the natural source from which codeine, morphine and diamorphine are obtained.
d. Circle two chiral carbons in the section of the Taxol structure below.

▶️Answer/Explanation

Markscheme
a. «drug» blocks/inhibits «viral» enzyme/neuraminidase/NA «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).

b(i).

Accept a circle that does not surround the amido group.
Do not accept a circle that only surrounds the phenol group.
b(ii)acterial 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 penicillin” for $M 2$.
Award [1 max] for “increased efficiency” OR “increased stability in GIT”.
Do not accept “bacteria develop tolerance”.
c(i)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»
c(ii)pium poppy/plants/seeds
Accept “poppy” OR “opioid”.

d.

\text { any two chiral carbons identified } \checkmark

 

 
 
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