A student diluted their egg white 50-fold before determining the enzyme activity

Question

A student diluted their egg white 50-fold before determining the enzyme activity in the extract. They used 0.6 mL of the dilute extract in their assay. The initial activity of this dilute extract was 0.030 delta A/min. Determine the number of units/mL originally present in the undilute egg white. Remember that one unit of activity in this assay is equal to an absorbance decrease of 0.001/min. Select one: a. 30 Units/mL b. 2.5 Units/mL c. 2500 Units/mL d. 50 Units/mL e. 900 Units/mL f. 0.05 Units/mL

Explanation / Answer

Let the initial concentration = x units / mL

It is diluted to 50 folds so the concentration will become = x units / 50 mL or 0.02 x / mL

0.6 mL of this will have 0.02 X 0.6 x units = 0.012 x units

Now one unit of activity in this assay is equal to an absorbance decrease of 0.001 / min

The assay for diluted extract = 0.030 A / min

for each unit the decrease is 0.001 / minute

So for x units = 0.001 x

0.012 xunit = 0.001 X 0.012 = 0.000012 x

Given 0.000012x = 0.030

x = 2500 units / mL

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