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2-simple passive difu.(9 oct) (3-net rate of diffu. Q (Fick's law of…
2-simple passive difu.(9 oct)
1- difus. down conc.
with rand. motion
equal distribution or conc.
mov. of molecules indepe. of other.
not apply with charged molec.
equl dist. of each molc. on either side
2-Flux: Fick's law of diffusion(J)
measuring the amount of difu. or mov. of molec.
def: no. of molec. that pass through certain area in a given amount of time
mol.cm -2. s-1
factors to consider:
we need conc. grad.
the larger the greater
ver. axis: conc.
diagram: outs. the cell: high conc.
decreases in linear way across the len of memb.
ins. low conc
thickness of memb.
inverse. proportional to the distance
the thicker the memb, the smaller the flux of the solote
carachteris. of the solutio.
' ' of the solute
difu. coefficient D
how easly a soliute can diffu. through that solu.
is influenced by:
fluid viscosity: depend: the substance that it id difus. through
R: universal gas constant
T: the absolute temp. higher temp higher flux
r: the size of the molec. = molecular radius of that molec
ralated to molecular waight: size of that molec.
1 more item...
the charge on the molec.
the charge is related to no. of hydrogen bonding groups present on that molec.
2 more items...
lipid solubility
the conc. of the solute in the lipid compared to the conc. of solute in aqueous solution
1 more item...
3-net rate of diffu. Q (Fick's law of diffu.)
diffu. constant
diffu. constant of the solute
permeability of solute and membrane=
4- Membrane permeability is influenced by:
-size,
-lipid solubility
-charge
diffu. well
small hydropho. molec.
small uncharged polar molec.
not diffu. well
large uncharged polar molec
ions
lipid solubility influences:
permeability
elec. charge
mov. of solutes across memb
5- Diffusion requires a permeable membrane
p>0
substance can permeate the memb.
with conc. grad. difu. down conc. grad.
thick arrow : down conc. grad.
thin arrow: rand. mov. of solutes>>>
solutes can move in either direc.
net move down conc. grad.
until equilibrium
p=0
memb. is impermeable to the substance
even if there is conc. grad. >>> no difu.
:question: D has B and MW in it so these factors are squared in final formula
