Why can bacteria rely on passive diffusion for their oxygen supply but human bei

Question

Why can bacteria rely on passive diffusion for their oxygen supply but human beings cannot? In the following, use the diffusion coefficient of oxygen in different substances from this table below.

(a) Calculate the time it takes for oxygen to diffuse from the environment to the centre of a bacterium of diameter 2.0 µm. (Bacteria are mostly comprised of water). Time in seconds

(b) Calculate the time it takes for oxygen to diffuse from the external air to an organ 19 cm below human skin. These two values give you a good approximation since humans consist of roughly 10 L extracellular fluid and 30L cells.

How many days does diffusion through water take?

How many days does diffusion through tissue take?

Explanation / Answer

Here ,

Tension in string , T = 100 N

length , L = 1.80 N

third harmonic , f3 = 72 Hz

fundamental frequency , f = f3/3

f = 72/3

f = 24 Hz

Now, f = sqrt(T/(m/L))/2L

24 * 2 * 1.80 = sqrt(100 * 1.80/m)

solving for m

m = 0.0241 Kg

m = 24.1 gm

the mass of string is 24.1 gm

a) for a bateria ,

distance , x = diameter/2

x = 2 um/2

x = 1 *10^-6 m

diffusion coefficient , D = 1 *10^-9 m^2/s

Now, time taken = x^2/(2*D)

time taken = (1 *10^-6)^2/(2 * 1 *10^-9)

time taken = 5 *10^-4 s

the time taken during diffusion is 5 *10^-4 s

B)

Now, for diffusion in human body

x = 0.19 m

for diffusion in water ,

time taken = x^2/(2*D)

time taken = (0.19)^2/(2 * 1 *10^-9)

time taken = 9.025 *10^15 s = 1.044 *10^11 days

diffusion through water will take 1.044 *10^11 days

Now, for diffusion through tissue

time taken = x^2/(2*D)

time taken = (0.19)^2/(2 * 1 *10^-11)

time taken = 9.025 *10^19 s = 1.044 *10^15 days

diffusion through water will take 1.044 *10^15 days

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