Ionic Distribution and Nernst Equation

Question 1

What is a voltage gradient?

Answer 1

separation of charges across a membrane

Question 2

What is the diffusion coefficient?

Answer 2

how fast an ion can defuse through a membrane barrier

Question 3

What are the 2 forces on an ion?

Answer 3

Chemical Force (concentration gradient + temp)
Electrical Force (charge + electrical gradient)

Question 4

What is diffusion potential?

Answer 4

Difference in diffusion coefficients
- K+ diffuse = greater (+) charge = diffusion potential

• positive potential repels (+) charge and attracts (-) charge
• Arc- diffuse to re-establish neutrality = no diffusion potential

Question 5

What happens when membrane is impermeable to anions?

Answer 5

• no (-) charge cross membrane
• accumulation of (+) charge – repels further K+ diffuse

Question 6

When will diffusion of K+ stop?

Answer 6

rate of chemical force = rate of electrical force
- electrochemical equilibrium

Question 7

What is the Nernst Equation?

Answer 7

E= RT/zF ln [K2]/[K1]

R = 2 cal/°K x mole
T = 273 + °C
z = valence of ion
F = 2.3 x10^4 cal/V x mole

Question 8

What is the ion distribution in:out of cell?

Answer 8

Na = 14:140
K = 150:5
Cl = 30:135