1.1 Cell structure

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Question 4
Medium

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 SampleNumber of algal cells counted
134
228
331
435
532

The dimensions of each grid area on the counting chamber are:

  • Width: 0.1 mm0.1\text{ mm}0.1 mm
  • Length: 0.1 mm0.1\text{ mm}0.1 mm
  • Depth: 0.025 mm0.025\text{ mm}0.025 mm
a.

Calculate the mean number of algal cells in the five samples.

[2]
b.

Calculate the total area of a grid area on the counting chamber in mm2\text{mm}^2mm2.

[1]
c.

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×depth

[2]
d.

Calculate 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 cells​

[2]

1.1 Cell structure Questions

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