Question 19M.3.sl.TZ1.15
| Date | May 2019 | Marks available | [Maximum mark: 3] | Reference code | 19M.3.sl.TZ1.15 |
| Level | sl | Paper | 3 | Time zone | TZ1 |
| Command term | Identify, Outline | Question number | 15 | Adapted from | N/A |
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]
«four-membered» beta-lactam ring [✔]
Note: Accept a diagram showing a structural representation of the beta-lactam ring.
Most students could identify the beta-lactam ring as the structural feature responsible for penicillin’s activity.
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]
produce penicillinase/enzyme that deactivates penicillin [✔]
The action of penicillinase/beta-lactamase was less well known with only about a third of students gaining this mark.
Outline how the structure of penicillin has been modified to overcome this resistance.
[1]
side-chain changed «preserving beta-lactam ring» [✔]
Note: Accept “R group changed”.
Most students were also aware that changing to the side chain of penicillin is often used to counter resistance, though many benefitted from the decision to accept “R-” without any mention of the data booklet structure.