The great chef and amateur scientist Kahpper Bowles was watching a Nova program

Question

The great chef and amateur scientist Kahpper Bowles was watching a Nova program on cell division one day when he wondered what the growth rate was of his new yeast that he bought (Super Fast Rise Yeast). So. he decided to put both normal yeast and SFR yeast in separate sugar and honey solutions and measure the rate at which the cells grow by determining the relative number of cells in each of the two solutions. Calibrating his spectrophotometer for actual number of yeast cells present, he used his spectrophotometer and obtained the following results: Time Number of Cells Present (cells/ml) (days) Regular Yeast SFR Yeast For the questions below, use the formulas k = In (N_f/N_2)/time and t_d = In (2)/k 1 & 2. What is the doubling-time for cell division (td) for the two types of yeast during the first seven days? 3 & 4. What is the doubling-time for cell division (td) for the two types of yeast during days 7 to 10? 5. Which type of yeast, if either, was growing fastest during the first week (days 1-7)? 6. For each of the cell types, determine if they grew more slowly in days 7-10 than they did during the first week (i.e. was growth during days 7-10 slower than days 1-7)? 7 & 8. If a yeast cell has an approximate volume of 50 mu m3, at day 7 what percentage of the total volume of the mixture is taken up by the yeast cells in each of the two yeast mixtures? [For problems 7 & 8, remember, the numbers given are concentrations (cells/ml) and that 1 ml = 1 cm3 and 1 pm = 10^-4 cm. so that 1 mu m^3 = (1 mu m)^3 = (10^-4 cm)^3 = 10^-12 cm^3]

Explanation / Answer

3&4.

The td can be calculated from the above formula,

Initial time =7

Final time =10

For yeast one,

Substituting the values in the above equation,

k=ln(81920/139264)/3

td=ln(2)/k

= 1.657 hrs.

For yeast 2,

k=ln(139264/312682)/3

td=ln(2)/k

= 2.571 hrs.

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