Question

Please help with the following!!!

Staphylococcus aureus is a spherical cell approximately 1.0 |mu m in diameter. Assuming it is almost entirely water with a density of 1 g/mL, Compute The mass of the bacterium in kg The mass of the bacterium in kD The number of water molecules it contains How many S aureus in a row would it take to circle the Earth? (Earth radius at the equator is 6378.1 km.) The surface area in m2 The number of phospholipid molecules in its plasma membrane, assuming each lipid molecule has an area of 0.50 nm2

Answer 1

a)

mass --> from density

D = m*V

d = 1 micrmeters = 1*10^-6 meters

V = 4/3*R^3 = (4/3)((10^-6)/2)^3 = 1.6666*10^-19 m3

for kg:

m = D/V = 1 g/mL * 1.6666*10^-19 m3 = 1 kg / L * 1.6666*10^-19 m3 =  1000 kg / m3 * 1.6666*10^-19 m3

m = 1.6666*10^-16 kg

b)

in kD ...

1 Da = 1.66*10^-27 kg

then

Da = (1.6666*10^-16 kg) / (1.66*10^-27 kg / Da) = 100397590361 Da = 100397590.361 kDa

c

if it is water...

1.6666*10^-16 kg of water = 1.6666*10^-19 g of water

1 mol = 18 g

x mol = mass/MW = (1.6666*10^-19)/18 = 9.2588*10^-21 mol

1 mol = 6.022*10^23 molecules

(9.2588*10^-21)*(6.022*10^23) = 5575.64 molecules of water

d)

Diameter = 1 micrometer = 1*10^-6 meters

N = Radius / Diameter = (6378.1*1000) / (1*10^-6) = 6.3781*10^12 bacterias