Membrane Potentials

Question 1

Are plasma membranes polarised?

Answer 1

yes

Question 2

What is membrane potential?

Answer 2

separation of opposite charges across the membrane

Question 3

What are the units for membrane potential?

Answer 3

mV

Question 4

Is the membrane itself charged?

Answer 4

No

Question 5

Which cells have the ability to produce rapid, transient changes in their membrane potential when excited (e.g. action potentials)?

Answer 5

excitable cells e.g. nerve and muscle cells

Question 6

When is resting membrane potential constant?

Answer 6

in non-excitable cells, and in excitable cells at rest

Question 7

What are the intracellular and extracellular values for chlorine?

Answer 7

extracellular - 110

intracellular - 7

Question 8

What are the intracellular and extracellular values for sodium?

Answer 8

extracellular - 150

intracellular - 15

Question 9

What are the intracellular and extracellular values for potassium?

Answer 9

extracellular - 5

intracellular - 150

Question 10

Is the resting membrane potential more permeable to potassium or sodium?

Answer 10

potassium (100x more)

Question 11

Which gradient, concentration or electrical, moves K+ into the cell?

Answer 11

electrical

Question 12

When both the electrical and concentration gradients acting on K+ are equal, what is this?

Answer 12

equilibrium potential for K+ (EK)

No further net movement of K+ would occur

Question 13

The equilibrium potential for any given ion can be calculated using what?

Answer 13

Nernst equation

Question 14

What is the equilibrium potential for sodium?

Answer 14

+60mV

Question 15

What is the equilibrium potential for potassium?

Answer 15

-90mV

Question 16

What is the value of the resting membrane potential?

Answer 16

-70mV

Question 17

What can be used to calculate the value of the resting membrane potential?

Answer 17

Goldman-Hodgkin-Katz equation

Question 18

What is a specialised use of membrane potential in nerve and muscle cells

Answer 18

Rapidly and transiently alter their membrane permeabilities in response to appropriate stimulation, resulting in fluctuations in Em.
Nerve impulses in nerve cells and triggering contraction in muscle cells.
Changes in Em linked to secretion of insulin from pancreatic beta-cells.

Question 19

What is the single most important factor in setting the cell membrane potential?

Answer 19

K+ equilibrium potential