Assume that a cell culture has a density of 108 cells/mL. You transfer 20 microliters (20 L) of this culture onto a microscope slide. How many cells do you expect will be in this 20 L drop you placed under the microscope?
To calculate the number of cells in the 20 μL drop, we need to know the cell density and the volume being transferred.
Given:
Cell density = 108 cells/mL
Transfer volume = 20 μL
First, we need to convert the transfer volume from microliters (μL) to liters (L) since the cell density is given in cells per mL.
1 mL = 1 x 10^-3 L
20 μL = 20 x 10^-6 L = 2 x 10^-5 L
Next, we can calculate the number of cells in the 20 μL drop by multiplying the cell density by the transfer volume in liters.
Number of cells = Cell density (cells/mL) x Transfer volume (L)
Number of cells = 108 cells/mL x 2 x 10^-5 L
Now, we can substitute the values and calculate:
Number of cells = 108 cells/mL x 2 x 10^-5 L
= 2.16 x 10^3 cells
Therefore, you would expect approximately 2,160 cells to be in the 20 μL drop you placed under the microscope.