Question 19N.3.hl.TZ0.25a
| Date | November 2019 | Marks available | [Maximum mark: 3] | Reference code | 19N.3.hl.TZ0.25a |
| Level | hl | Paper | 3 | Time zone | TZ0 |
| Command term | Explain | Question number | a | Adapted from | N/A |
The discovery of penicillins contributed to the development of antibiotics.
Explain how the beta-lactam ring is responsible for the antibiotic properties of penicillin. Refer to section 37 of the data booklet.
[3]
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
amido/amide group «in ring» is «highly» reactive ✔
«irreversibly» binds/bonds to enzyme/transpeptidase
OR
inhibits enzyme/transpeptidase «in bacteria» that produces cell walls
OR
prevents cross-linking of «bacterial» cell walls ✔
NOTE: Accept arguments using correct descriptions of hybridization for M1.
Do not accept "breaks/binds to cell walls" – a reference to the enzyme is needed for alternatives 1 and 2 for M3.
Do not accept "cell membrane" for "cell wall".
