In a hypothetical cell the intracellular and extracellular environments
differ in that the concentration of chloride
outside the cell is 500mm ([Cl]o=500mm) and the concentration of chloride
inside the cell 100mm ([Cl]i=100mm)
. All other ions are equally concentrated on the inside and outside.
1. Given the above situation what electrical potential would be required
to exactly balance the force generated by
the chemical gradient? Be able to show your work.
2. At equilibrium is the inside or the outside relatively negative?
3. This is somewhat of a trick question. What is the Nernst potential
for potassium
(permeable to a single ion species)
In a hypothetical cell the intra and extracellular environments are
as follows:
inside
outside
Sodium
50
440
Chloride
100
560
Calcium
.4
10
Potassium
400
20
1. What would the membrane potential be if the membrane were only permeable
to potassium? Be able to show
your work.
2. What would happen to the membrane potential if the concentration
of potassium in the extracellular media were
doubled? Explain.
3. What would the membrane potential be if the membrane were only permeable
to calcium?
(permeable to a multiple ion species)
In a hypothetical cell the intra and extracellular environments are
as follows:
inside outside
ratio of permeabilities
Sodium
50 337
.019
Chloride
41 340
.381
Calcium
.04 10
.002
Potassium 168
6
1
1. What would the membrane potential be if the membrane were only permeable to potassium and sodium?
2. What would the membrane potential be if the membrane were permeable to all ions?
3. Does the membrane hyperpolarize or depolarize when the potassium conductance increases? Why?