b) Cell counting techniques (4)

Question 1

Haemocytometer

Answer 1

A haemocytometer is a specialized microscope slide with a grid used for counting cells in a liquid sample. The number of cells within a defined volume of the grid is counted, and this allows the total cell concentration in the sample to be calculated.

Question 2

Trypan Blue

Answer 2

Trypan Blue is a dye used to distinguish between viable and non-viable cells during counting. Living cells exclude the dye and remain clear, while dead cells take up the dye and appear blue, allowing for an accurate count of viable cells.

Question 3

Serial Dilution

Answer 3

Serial Dilution is used when the cell concentration is too high to count directly. A series of stepwise dilutions is performed to reduce cell density, and the number of cells in a diluted sample is counted, then multiplied back to estimate the original concentration.

Question 4

Automated cell counters

Answer 4

Automated cell counters use image analysis or electrical impedance to rapidly count cells in a sample. These machines can also differentiate cell types and assess viability, providing a faster alternative to manual counting with a haemocytometer.