Question

Lab 15 Review esults Date Section LE 15-1 Cell Counts quare number Cell number (live) Cell number (dead) % Viability 1 2 3 Record your cell counts in Table 15.1. Do not calculate the % viability yet. WHY must you count the number of cells in at least four different squares? ivity 3: Calculating the number of cells per milliliter You have counted the number of cells in 0.004 mm of sample. This is not your final answer. Remember: your are being asked to calculate the number of cells in one milliliter of sample, not the number of cells per square You now need to do some math. First, calculate the AVERAGE number of cells in your sample. Do this by adding the 4 numbers from th squares you counted, and then divide this number by 4. For example, if your counts were 12, 14, 15, 10 your average number is 12.75 Write your average number of cells in the block below. Do not round up - record your number with t decimal points. 1.75 Direct Counting Using the Hemocytome LAB 15 tifying Microbial Growth

Answer 1

The suspension loaded on to hemocytometer is assumed to be uniform suspension. However, in practice, the cells may not be uniformly present as single cells. Cells can be clumped. The counting of four separate square will prevent the bias or error that may result. The average number of cells obtained from the 4 squares will give a better representation of what the actual cell count is.

The large squares also allow counting of cells easier. The border gridlines also help to decide whether to count the cell or not.

It is asked not to count the actual % viability in the table 15.1. This is because the % viability is calculated from the average number of cells and not from individual cell count.

Average number of cells= Adding Total number of cells from each square/4

Total number of cells in each square= Dead cell+ viable cell

Total number of cells in square 1= 1+6=7

Total number of cells in square 2= 3+4= 7

Total number of cells in square 3= 1+ 3= 4

Total number of cells in square 4= 2+4= 6

Average number of cells= (7+7+4+6)/4= 24/4= 6

Please note that the 1.75 that is shown is average number of viable cells in suspension (1+3+1+2/4=7/4= 1.75). This is not average number of cells in suspension.

Answer should be 6.