In: Biology
At 2 pm, you start a culture of microbe with 2,000 cells. The cell growth has a lag phase of 4 hours. At 9 pm, the culture enters stationary phase with 128,000 cells. How many cells does this culture have at 8 pm? a. 4,000 b. 8,000 c. 16,000 d. 32,000 e. 64,000
SHOW YOUR WORK
Given,
Nt1 = 128,000 cells
No = 2000 cells
n1 = number of generations
t = time
Therefore, using general equation for growth curve
Nt1 = No x 2n1
128,000 = 2000 x 2n1
2n1 = 64
2n1 = 26 (64 = 26)
n1 = 6
Number of generations (n1) = 6
time (t2) = 2 hrs (this is because starting from 2 p.m. till 6 p.m. there was lag phase so no growth and after 6 p.m. log phase initiates, so given at 8 p.m. the time till be 2 hrs :(8p.m -6p.m.))
At t1 =3 hrs previously, n1 = 6
So, at t = 2 hrs now, n2 = 6/3 x 2 = 4
Hence number of generation at 8 p.m. is 4 (n2)
Therefore, using equation to calculate number of cells at 8 p.m. i.e after 2 hrs
Nt2 = No x 2n2
= 2000 x 24
= 2000 x 16
= 32,000
Hence, Nt2 after 2 hrs at 8p.m. is 32,000 cells
So, option d is correct.