An aquaculture scientist wants to estimate the cell concentration of a unicellular green alga (Chlorella vulgaris) in a photobioreactor suspension using a counting chamber under a light microscope. The table below shows the number of algal cells counted across five separate grid areas on the counting chamber:
| Grid Sample | Number of algal cells counted |
|---|---|
| 1 | 34 |
| 2 | 28 |
| 3 | 31 |
| 4 | 35 |
| 5 | 32 |
The dimensions of each grid area on the counting chamber are:
Calculate the mean number of algal cells in the five samples.
Calculate the total area of a grid area on the counting chamber in mm2\text{mm}^2mm2.
Calculate the volume of a single grid area of the counting chamber in mm3\text{mm}^3mm3 using the equation:
volume=area×depth \text{volume} = \text{area} \times \text{depth} volume=area×depthCalculate the mean number of algal cells per mm3\text{mm}^3mm3 of the suspension using the equation:
mean number of cells per mm3=mean number of cellsvolume of counting chamber \text{mean number of cells per }\text{mm}^3 = \frac{\text{mean number of cells}}{\text{volume of counting chamber}} mean number of cells per mm3=volume of counting chambermean number of cells163 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.