Lecture 4

CHE 618

Membrane transport

Role of pH

Solvents

Metabolism and transport

)( recsource CCPJ Permeability, m/s

Flux

Fick’s Law

Concentration (molarity, …)

Diffusion-limited mechanism:Diffusion-limited mechanism:

Jdiff = Dm/lm ([M]m,s)

[M]m,s = Kex[M]

Jdiff = Dm/lm• Kex[M]

P = (DmKex)/lm

permeability

Water Membrane Water

layerBoundary Boundary

layer

ls

lm

l r

Js = Ds/ls ([M]s - [M]m,s) Jin = k1[M]m,s - k-1[M]m,s

Jdiff = Dm/lm ([M]m,s - [M]m,r)

Jout = -k1[M]m,r + k-1[M]m,r Jr = Dr/lr ([M]m,r - [M],r)

DMSO

b.p. 189 C

Poly(ethylene oxide)

Solvent-facilitated transport

Carrier – facilitated transport

Active transort

Ion channels and ion pumps

First-order process

DRUG half-life(hours)

Penicillin 0.5Insulin 0.7Aspirin 6Tetracycline 9Sulfadimethoxine 30Vitamin D 40

First-order elimination kinetics

log C

time

log C

time

One-compartment kinetics Two-compartment kinetics

[B]

time

First order consecutive process

¼ mg /mL cocaine

0.05-0.10 mg/mL cocaine

Cocaethylene

H

Methylecgonine

benzoylecgonine

Ecgonine

3-hydroxy-8-methyl-8-azabicyclo [3.2.1]octane-2-carboxylic acid

Cocaine metabolic profile. BE-benzoylecgonine, EME-ecgonine methyl ester,CE- cocethylene

6-MAM