1. You are given a 500 ml culture of Euglena from which a 1 ml sample is taken a
ID: 142865 • Letter: 1
Question
1. You are given a 500 ml culture of Euglena from which a 1 ml sample is taken and put in 49 ml of water. Absorbance was measured on this sample but the reading was off the scale. One ml of this solution is taken and diluted in another 249 ml of water, and this time, the OD675nm gave the reading of 0.27. If the turbidity of 0.27 corresponds to 4 x 10^5 cell/ml, calculate the total cell number in the original culture.
2. When extrapolating the value of an unknown sample from a standard protein curve, a scientist obtained a result although all of her unknowns were higher in concentration than the highest standard. What is the problem with this approach and how can the experiment be rectified?
Explanation / Answer
1) The density of euglena in the final solution is 4 x 10^5 cell/ml. The solution is diluted twice to the tune of 1:12500.
The concentration of euglena in 1/12500 solution is 4 x 10^5 cells/ml
So, the density of euglena in original solution is,
= 4 × 10^5 × 12500
= 50000 × 10^5
= 5 × 10^9 cells/ml
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