A technician grows one species of bacterium in nutrient broth. The broth will be spread onto nutrient agar to make a lawn for an antibiotic test.
| Time the culture was started | Starting number of bacteria | Mean division time | Minimum number needed for the lawn |
|---|---|---|---|
| 09:20 | 2.0 × 104 | 25 minutes | 3.0 × 105 |
The conditions remain suitable for bacterial division.
The table shows how repeated divisions change the population.
Give the missing multiplication factor.
| Number of completed divisions | 0 | 1 | 2 | 3 | 4 |
|---|---|---|---|---|---|
| Population as a multiple of the starting population | 1 | 2 | 4 | 8 | ? |
Calculate the number of bacteria in the broth after four divisions.
State whether the broth then contains enough bacteria to make the lawn.
The technician spreads the broth onto the agar as soon as the fourth division is complete.
Calculate the time of day when the broth is spread onto the agar.
282 exam-style questions on AQA GCSE Biology 1.1 Cell structure, covering 1.1.1 Eukaryotes and prokaryotes, 1.1.2 Animal and plant cells, 1.1.3 Cell specialisation, 1.1.4 Cell differentiation, 1.1.5 Microscopy, and 1.1.6 Culturing microorganisms. Each one has a worked solution and a mark scheme showing where the marks go.