| Date | May 2016 | Marks available | 3 | Reference code | 16M.3.sl.TZ0.16 |
| Level | SL | Paper | 3 | Time zone | TZ0 |
| Command term | Explain | Question number | 16 | Adapted from | N/A |
Question
Penicillin was one of the first antibiotics to be isolated and identified for its ability to treat bacterial infections.
Explain the importance of the beta-lactam ring in the antibiotic activity of penicillin.
Identify two dangers of the overuse of antibiotics.
Markscheme
ring is «sterically» strained
OR
angles of 90° instead of 109.5/109/120° angles
OR
angles smaller than 109.5/109/120°/tetrahedral/trigonal planar/triangular planar angle
ring breaks up/opens/reacts «easily»
OR
amide/amido group «in ring» is «highly» reactive
binds to/reacts with/interferes with/inactivates transpeptidase/enzyme
responsible for bacterial cell wall formation/cross-linking
Do not accept “cell membrane” for “cell wall”.
Accept “bonds to” for “binds to” in M3
Any two for [1 max] from:
leads to «bacterial» resistance «of antiobiotics»
OR
makes antibiotics less effective
OR
increased side effects due to larger dosages
proportion of resistant bacteria increases
destroys useful/beneficial bacteria
OR
destroyed bacteria replaced by more harmful bacteria
resistant bacteria pass on their resistance/mutation to next generation
damage to ecosystems
Accept “superbugs such as MRSA develop” but superbug must be identified.
