Question

The concentration of a biomolecule inside a rod-shaped prokaryotic cell is 0.0015M. Calculate the number of molecules inside the cell which is 4.8um long and 1.2um in diameter.

Answer 1

diameter = 1.2 um

diameter = 1.2*10^-6 m

r = diameter / 2

= (1.2*10^-6 m ) / 2

= 6.0*10^-7 m

length = 4.8 um = 4.8*10^-6 m

volume of cylinder = pi*r^2*length

= pi*(6.0*10^-7 m)^2 * (4.8*10^-6 m)

= 5.43*10^-18 m^3

= 5.43*10^-15 dm^3

= 5.43*10^-15 L

molarity = number of mol / volume

0.0015 = number of mol / 5.43*10^-15 L

number of mol = 8.14*10^-18 mol

number of molecules = number of mol * 6.022*10^23

= 8.14*10^-18 * 6.022*10^23

= 4.90*10^6 molecules

Answer: 4.90*10^6 molecules