Prednisone is an anti-inflammatory corticosteroid that is converted by the liver to an active drug form, prednisolone. T

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Prednisone is an anti-inflammatory corticosteroid that is
converted by the
liver to an active drug form, prednisolone. To measure the ability
of prednisolone to enter cells, researchers
measure the partition coefficient (K D) between octanol and water.
Following separation of the drug between
organic and aqueous phases, they find prednisolone solubility in
octanol is 7.5 mg/mL while solubility in the
water is 1.92 mg/mL.
a) Into which layer (water or octanol) does most of the drug
preferentially partition?
b) What is the calculated partition coefficient (K D)?
c) Given the thickness of the cell membrane is 2.5 nm and the
diffusion coefficient of prednisolone
in the lipid bilayer is 6×10 -7 cm2s -1, what is the permeability
coefficient in units of cm/s?
d) If previously untreated cells are in culture are exposed to
media containing 5 μM prednisolone,
what is the initial diffusion rate of drug into the cells in mol/s?
The average cell diameter is 20 microns
and the drug’s molecular weight is 360g/mol. You can assume the
cells are in suspension, so they are
roughly spherical and exposed to media on all sides.