Flashcards in Ions, Permeability and the Resting Membrane Potential Deck (13):

1

## What are the three most important factors which determine the 'passive' movement of an ion across the membrane?

###
+ Electrical gradient

+ Concentration gradient

+ Membrane permeability

2

## What is equilibrium potential?

### When the electrical potential precisely offsets the tendency for K+ to diffuse down its concentration gradient (chemical potential difference)

3

## What is the magnitude of the equilibrium potential?

### The greater the chemical potential gradient ( conc. gradient) across a membrane, the greater the electrical gradient required to offset it

4

## In the Nernst equation, what is R?

### R = gas constant

5

## In the Nernst equation, what is T?

### T = absolute temperature

6

## In the Nernst equation, what is F?

### F = Faraday constant

7

## In the Nernst equation, what is z?

### z = valency

8

## What does the Nernst equation prove?

### That the equilibrium potential is proportional to the logarithm of the ratio of the concentrations in the two compartments.

9

## What is the Nernst equation for a monovalent ion at 37°C?

### Ex = 61 x log base10 x conc. of chamber 1 / conc. of chamber 2

10

## What is the Nernst equation for a divalent ion at 37°C?

### Ex = 30.5 x log base10 x conc. of chamber 1 (outside) / conc. of chamber 2 (inside)

11

## What is the net difference between the distribution of Cl- ions and that of Na+ and K+ ions?

###
+ Cl- ions are passively distributed

+ According to the value of the membrane potential - intracellular Cl- ions concentration is set by the membrane potential

+ Na+ and K+ ion concentrations are maintained by the sodium pump and set the membrane potential

12

## Why is the resting membrane potential a negative value?

### Because K+ ions are not accompanied by anions, charge separation occurs and the electrical potential of the cell interior becomes negative with respect to the extracellular solution.

13