Question

The gut epithelium, which is about 5.5 nm thick, acts as a barrier to drugs. Take for example caffeine, which has a diffusion coefficient in the epithelium equal to 1.1x10^-11 cm2/s. If the concentration of caffeine in the gut is 1x10^-6 moles/cm3, and assuming the concentration inside the body is zero, calculate the flux of caffeine across the gut epithelium. solve in moles/(cm2.s) (b) If the gut surface is 1x10^4 cm2, and assuming that the caffeine flux is maintained at the level calculated in part (a), how long will it take for 1x10^-6 moles of caffeine to diffuse into the body? solve in s

Answer 1

Hi,

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PART A:

We know that, According to Fick's first law, Flux of diffusion is given by,

Where,

is the Diffusion Coefficient (cm²/s).

is the change in concentration (moles/cm³).

is the thickness/distance of diffusion surface (cm)

Given that,

Diffusion Coefficient of caffeine,

Change in concentration=Concentration of caffeine inside body Concentration of caffeine in gut.

Thickness/distance of diffusion surface,

Flux is given by,

PART B:

We know that, According to Fick's first Law, Time for diffusion is given by,

Where,

is the no.of moles of solute (moles).

is the flux (moles/cm².s).

is the area of diffusion (cm²).

Given that,

No.of moles of solute/caffeine,

Flux,

Area of diffusion,

Time for diffusion is given by,

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