| Date | May 2013 | Marks available | 2 | Reference code | 13M.3.HL.TZ2.8 |
| Level | Higher level | Paper | Paper 3 | Time zone | Time zone 2 |
| Command term | Outline | Question number | 8 | Adapted from | N/A |
Question
Outline how bacteria can be classified by Gram staining.
Markscheme
a. Gram stain permits classifying bacteria according to structure of their cell walls;
b. Gram-positive bacteria have thick peptidoglycan layer and Gram-negative a thin layer with an outer membrane;
c. giving different pathogenic/resistance properties;
d. Gram-positive bacteria appear purple / Gram-negative pink/reddish;
Examiners report
Most knew about Gram staining, but some confused the characteristics between Gram+ and Gram-.
Syllabus sections
Option B: Biotechnology and bioinformatics » Option B: Biotechnology and bioinformatics (Core topics) » B.1 Microbiology: organisms in industry
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