PRINCIPLES OF MODERN MICROBIOLOGY
Mark Wheelis
ANSWERS TO STUDYQUESTIONS
CHAPTER 1
Introduction to Microbiology
2. The procaryotic cell is small and structurally simple compared to thee eucaryotic cell. It has a
nucleoid instead of a membrane-bound nucleus, and it is rarely compartmentalized by intracellular
membranes.
4. Before we can calculate concentrations, we have to convert cell volume in m3 to liters. We can do
this by recognizing that one milliliter is equal to 1 cubic centimeter:
10-3 L = 1 cm3 = (104 m)3 = 1012 m3
thus 1 L = 1015 m3 and 1 m3 = 10-15 L
Now we can solve for small molecule concentration:
(8 X 10-15 g/cell) / (200 g/mole) = 4 X 10-17 moles/cell
(4 X 10-17 moles/cell) (1015 L/cell) = 4 X 10-2 moles/L = 40 mM
6. (10-3 moles/L) (6 X 1023 molecules/mole) (10-15 L/cell) = 6 X 105 molecules/cell
8. If it takes 4 X 10-2 moles of ATP to make one gram of cells, it takes
(4 X 10-2 moles/g) X (3 X 10-13 g/cell) = 12 X 10-11 = 1.2 X 10-10 moles of ATP to make one new
cell, or
(1.2 X 10-10 moles/cell) X (6 X 1023 molecules/mole) = 7.2 X 1013 molecules ATP to make one new
cell.
In question 6 we calculated that each cell has a pool of ATP of about 6 X 105 molecules, so
(7.2 X 1013 molecules/new cell) / (6 X 105 molecules/pool) = 1.2 X 108 pools/new cell).
Since it takes 40 minutes = 2.4 X 103 seconds to make a new cell, the ATP pool turns over
(2.4 X 103 seconds/new cell) / (1.2 X 108 pools/new cell) = 2 X 10-5 seconds, or 20 microseconds for
the ATP pool to turn over.