Caroline O’Connor, Melissa Pollesch, John Nguyen, Michelle Boulanger
Lab 7: Membrane Transport
T.A. James Peterman
Ions are flowing normally without counter current, and the ion flux
represents Na+ flux when counter current is applied.
Application of a counter current will inhibit passive diffusion of Cl- ions
through the tight junctions; however, ion flux still is only represented by Na+ flux;
predict that there will be no difference in amperage and no change in ion flux between the control
conditions in A and the experimental conditions in B.
same as control above
Na+ free Ringer’s/Na+ free Ringers:
Because of the absence of Na+ ions, we predict that
there will be no change in amperage, thus no electrical potential, and no ion flux.
Na+ free Ringer’s/Ringer’s:
ATPase Na+/K+ pump is still functionally pumping 3 Na+ ions out
and 2 K+ ions in; however, because there is no Na+ present on the mucosal side,
we predict that there
will eventually be little to no electrical potential, and no ion flux.
same as controls above
Because of the low driving force of Na+ to passively diffuse into
the cell due to a low concentration gradient,
we predict that electrical potential will be lower than the
control and that ion flux will significantly decrease.
At around a 60% concentration of Ringer’s, the Na+ channels will
begin to become saturated: therefore,
we predict that the rate of ion flux will eventually plateau, and
little change will be observed in electrical potential or ion flux.
100% and 120% Ringer’s/Ringers:
we predict that, because of the same saturation concept
in H, there will be no change in electrical potential or ion flux.
Ringer’s/ouabain (over 10 min):
Ouabain works to destroy the ATPase Na+/K+ pump.
Therefore, Na+ will only be passively diffusing through the mucosal side of the membrane. However,
passive diffusion will eventually reach equilibrium.
We predict that, over time, electrical potential
will decrease until it reaches a plateau, and that ion flux will decrease until in reaches 0.