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Date May 2019 Marks available 1 Reference code 19M.3.hl.TZ1.20
Level HL Paper 3 Time zone TZ1
Command term Outline Question number 20 Adapted from N/A

Question

Staphylococcus aureus (S. aureus) infections have been successfully treated with penicillin and penicillin derivatives.

Identify the feature in penicillin responsible for its antibiotic activity.

[1]
a.

The widespread use of penicillin and its derivatives has led to the appearance of resistant S. aureus strains.

Outline how these bacteria inactivate the antibiotics.

[1]
b(i).

Outline how the structure of penicillin has been modified to overcome this resistance.

[1]
b(ii).

Markscheme

«four-membered» beta-lactam ring  [✔]

 

Note: Accept a diagram showing a structural representation of the beta-lactam ring.

a.

produce penicillinase/enzyme that deactivates penicillin  [✔]

b(i).

side-chain changed «preserving beta-lactam ring»  [✔]

 

Note: Accept “R group changed”.

b(ii).

Examiners report

Most candidates correctly identified the feature in penicillin responsible for its antibiotic activity.

a.

Most candidates could outline how bacteria inactivate the antibiotics.

b(i).

Outlining how the structure of penicillin has been modified was less well answered, with many candidates referring to functional groups rather than the side chain or R group.

b(ii).

Syllabus sections

Options » D: Medicinal chemistry » D.2 Aspirin and penicillin
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