Question 18N.3.hl.TZ0.16
| Date | November 2018 | Marks available | [Maximum mark: 6] | Reference code | 18N.3.hl.TZ0.16 |
| Level | hl | Paper | 3 | Time zone | TZ0 |
| Command term | Explain, State, Suggest | Question number | 16 | Adapted from | N/A |
The structure of penicillin is shown in section 37 of the data booklet.
State the internal bond angles in the b-lactam ring and the expected bond angles in sp2 and sp3 hybridised atoms.
[2]
Accept “109º”.
Explain how the open β-lactam ring kills bacteria.
[2]
«irreversibly» binds/bonds to enzyme/transpeptidase
OR
inhibits enzyme/transpeptidase «in bacteria» that produces cell walls
OR
prevents cross-linking of bacterial cell walls ✔
cells absorb water AND burst
OR
cells cannot reproduce ✔
Accept “reacts with” for “bonds to” for M1.
Do not accept “cell membrane” for “cell wall” for M1.
Accept “cells burst due to osmotic pressure” for M2.
Accept “bacteria” for “cells” for M2.
State how the structure of penicillin can be modified to combat the effect of resistance caused by over prescription.
[1]
«modify» side-chain ✔
Accept “«modify» R”.
Suggest why human cells are not affected by penicillin.
[1]
no cell walls
OR
humans do not have transpeptidase ✔