CB24 Membrane Potentials

Question 1

Define equilibrium potential & electrochemical gradient

Answer 1

Equilibrium potential - voltage where the movement of ions down concentration & electrical gradients is equal

Electrochemical gradient - the difference of electrical & chemical charges across a differentially permeable membrane

Question 2

Explain how ion concentration gradients & selectivity in the membrane permeability results in a membrane potential

Answer 2

The Goldman equation determines the resting membrane potential. Em is a combination of the equilibrium potentials of membrane permanent ions

• the resting cell membrane highly permeant to k+ (due to K+ leak channels) therefore Em is closest to Ek+

Question 3

Appreciate the key role of k+ leakage channels

Answer 3

A number of k+ leak channels are open in the resting cell
These allow k+ to leak out of the cell down its concentration gradient
Generates a subtle difference in charge over the membrane - membrane potential

Question 4

Describe the indirect significance of the sodium-potassium pump for the maintenance of membrane potential

Answer 4

Sodium-potassium pump responsible for the unequal distribution of Na+ & k+ ions across the membrane

Concentration gradients & membrane permeability to k+ & Na+ ions are the most important factors in determining a cell’s resting membrane potential

Question 5

What is the Nernst equation used to calculate?

Answer 5

Used to calculate the equilibrium potential of an ion

Question 6

What is the Goldman equation used to calculate?

Answer 6

Determines the resting membrane potential