| Date | May 2012 | Marks available | 4 | Reference code | 12M.3.hl.TZ1.D2 |
| Level | HL | Paper | 3 | Time zone | TZ1 |
| Command term | Identify | Question number | D2 | Adapted from | N/A |
Question
Many diseases are the result of infection of the body by either bacteria or viruses.
Identify the particular structural feature of penicillins that is responsible for their action and explain how this prevents bacteria multiplying.
Markscheme
4-membered ring/\(\beta \)-lactam ring;
easily broken / very reactive / highly strained ring;
binds to proteins/deactivates proteins that form cell wall / interferes with cell wall formation / prevent formation of crosslinks within cell wall;
makes cell wall porous / allows water to pass;
causes cell to burst;
Examiners report
Most candidates knew that AIDS was a viral disease, but knowledge of a bacterial disease (rather than the name of a bacterium) was more sketchy. The differences between bacteria and viruses and reasons for drug resistance in bacteria were generally well known. Many candidates also gave good answers about the mode of action of penicillin, but the action of antiviral drugs could only be explained by the best candidates.
