3. Now put a second red dot on the best fit line that is at exactly the double t

Question

3. Now put a second red dot on the best fit line that is at exactly the double the OD of the first Record the time and OD for that second point. Since the OD doubl from the first to the second point, cenls must have doubled. Therefore, the time it took to go from the first OD reading to cond b reading is the time it took for the culture to double. That is one generation time!!! se the two pairs of numbers you have marked to calculate the generation time for the culture you grew. (Different cultures may give different generation times .) minutes OD at 1t red OD at 2nd red dot8 Generation time 3o minute 1 15 Time at 1st red dot ·25g 45 minutes Time 2nd at red dot 3. If you are told that a culture has an OD reading of 0.03 when there are one million cells per ml, how many cells per ml are present when the OD reads 0.015? 4. For the culture in question 3, what should you expect to get as an OD reading on a sample with six million cells/ml? 5. If you test a sample and find out that one million cells/ml of Escherichia coli has an OD reading of 0.23, would you expect the same OD, a higher or a lower OD if you had one million fungal cells? Explain your answer

Explanation / Answer

3- As the OD is directly proportional to a number of cells per ml. So as the OD doubles the cell number also doubles.

So number of cells in 0.015 OD will be 0.5 million

4- 0.3 OD represents 1 million cells

So 0.6 OD will represent 2 million cells

1.2 OD will have 4 million cells

2.4 OD will have 8 million cells.

So for 6 million cells, OD should be around 2

5-

normally 1 OD of E-coli cells are 8*108 cells

1 -OD of yeast cells are around 2*107 cells

So for One million of Yeast cells, there will be higher OD than Ecoli's one million cells, as the number of cells in yeast is less as compared to E-coli

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