Lecture 5: Membrane Potential

Question 1

Ohm’s Law

Answer 1

-Calculated conductance (Charge)

I=V/R

I= Conductance
V=Driving force (volts)
R=Resistance

• Conductance is inverse to resistance
• Conductance is direct to driving force

Question 2

Membrane potential (Vm)

Membrane potential at rest

Answer 2

Membrane Potential:

• Ability for ions for more in/out membrane
• Net effect of all charge movements taking place across a membrane
• Usually most effected by K+

Membrane potential at rest: Ion gates are closed, but continuous influx k+ (creating negative charge inside)
Na - K ATPase=rest

Question 3

Electrochemical Equilibrium Potentials

Answer 3

• Net movement of each ion
• Driven by chemical gradients (concentration differences) and electrical gradients (Charge differences)
• When electrical and chemical gradients balance each other out the overall net movement of an ion is 0
• When gradients are uneven the membrane generates a specific electrical charge gradient

Question 4

Equilibrium Potential

Answer 4

Nernst equation:

Equilibrium potential (Em) = -60/z x log (inside conc./outside conc.)
-z= valency (aka charge # of ion)

Question 5

Membrane potential (vm) and Equilibrium potential (Eion)

Answer 5

The bigger the driving for flux when Vm and Em are equal

Question 6

Driving Force

Calcs

Direction

Answer 6

DF= Vm - Em

Vm= Given resting membrane potential (given)
Em= Electrical potential for a specific ion

Directions:
Efflux = same signs
Influx = opposite signs