Flux through membranes
- Assume membrane in steady state as before
- concentrations of charge charge can't change so current is constant
- Four inputs: voltage on inside and outside, concentration on inside and outside
- Jn = Gn(Vm − Vn)
- (electrical conductivity)
- always greater than zero, means transport will always go down electrochemical gradient (lose energy)
- Not really constant (depends on concentration) but in real cells, will seldom see much change in concentrations so we will assume Gn is constant.
- Vm = ψ(0) − ψ(d) (potential difference across membrane)
- (Nernst equilibrium potential)
- this constant is part of the model and not directly measurable (not physical)
- is electrical representation of chemical phenomenon
- But can indirectly measure this by changing Vm. The Nernst potential is the same potential that when applied externally to the membrane causes no current.
- at room temperature
- , so can use