Chapter 3.5: Membrane Potential

Question 1

what is an excitable cell?

Answer 1

a cell that is capable of getting electrically excited, resulting in an action potential that can be used as a signalling mechanism

Question 2

____ must be performed in order to separate opposite charges

Answer 2

work. (requires energy)

Question 3

the electrical ___ of ____ between the oppositely charged ions can be harnesed to perform work when the charges are permitted to come together in

Answer 3

force of attraction

Question 4

membrane potential

Answer 4

the difference in charges between the ECF and ICF.

Question 5

Resting membrane potential

Answer 5

the difference in charge across a membrane when the cell is not firing.

Question 6

what is the resting potential?

Answer 6

-70mV

Question 7

electrical potential= potential ___

Answer 7

difference

Question 8

voltage

Answer 8

the potential energy per unit charge. Measured in volts.

Question 9

movement of charge

Answer 9

current

Question 10

lipids are (good/bad) conductors

Answer 10

bad conductors. they are isolators

Question 11

how does a membrane act as a capacitor?

Answer 11

it maintains charge separation by storing opposite charge on either sides of the membrane.

Question 12

the thinner the membrane, the ____ its capacitance

Answer 12

larger its capacitance.

Question 13

How is resting potential maintained?

Answer 13

1) Na+/K+ ATPase pump: 3Na+ ions out for every 2K+ it transports in. the pump does create the potential, but it does maintain it once its been created

2) different solubilities and affinities for cell protein.
K+ is more soluble in internal H2O than Na+ because K+ has a smaller HYDRATION SHELL and is attracted to the A- proteins since it can bind easier.

3) K+ leak channels which allow the constant efflux of K+ out of the cell.

Question 14

How to calculate equilibrium potential of an ion?

Answer 14

nernst equation

Question 15

when there is no note movement of K+ from contending concentration or electrochemical gradients, the membrane is in ___ ____

Answer 15

equilibrium potential.

Question 16

what will happen to K+ if the membrane is at its equilibrium potential?

Answer 16

it will stop flowing into the cell because the K+ efflux from concentration gradient = K+ influx from concentration gradient. there is no net movement.

Question 17

the greater the permeability of the plasma membrane for a given ion, the greater the tendency for that ion to drive the membrane potential towward its ___ ___ ____

Answer 17

own equilibrium potential.

Question 18

why is resting potential so close to K+ equilibrium potential?

Answer 18

because the membrane is very permeable to K+. the resting potential is not exactly the potential of K+ because there is still some influence of sodium.

Question 19

What is the Goldman Hodgkin Katz equation?

Answer 19

takes into account the relative permeabilities and concentration gradients of all permeable ions to predict the RESTING potential in a cell membrane

Question 20

at resting potential, Na+ is ____ from ____(in terms of equilibrium)

Answer 20

far from equilibrium

Question 21

at what point would K+ move back into the cell if leak channels were open?

Answer 21

once K+ reached passed equilibium potential (past -90mv)

Question 22

why does Cl- remain on the outside of the cell?

Answer 22

the Na+/K+ ATPase pump pushes more and more Na+ out of the cell, creating a more positive ECF. The Cl- is more attarcted to the positive ECF than the (relatively) negative ICF.