Membrane potential

Question 1

Is sodium higher inside or outside the cell?

Answer 1

Outside

Question 2

Is potassium higher inside or outside the cell?

Answer 2

Inside

Question 3

Is calcium higher inside or outside the cell?

Answer 3

Outside

Question 4

Is chloride higher inside or outside the cell?

Answer 4

Outside

Question 5

What are properties of active transporters?

Answer 5

1. Actively move selected ions against concentration gradient2. Create ion concentration gradients

Question 6

What are properties of ion channels?

Answer 6

1. Allow ions to diffuse down concentration gradient2. Are selectively permeable to certain ions

Question 7

What constitutes the chemical force on an ion?

Answer 7

Only due to the chemical concentration gradient

Question 8

What is provided by the Nernst equation?

Answer 8

Strength of the chemical driving force due to the concentration gradient of an ion

Question 9

What is the Nernst potential?

Answer 9

1. Value of a (hypothetical) membrane potential which would prevent any net diffusion of the ion2. Hypothetical electrical force equal and opposite to the chemical driving force due to the chemical gradient

Question 10

What is the principle of electroneutrality?

Answer 10

Any macroscopic region of a solution must have equal number of positive and negative charges

Question 11

At rest is the membrane potential closer to Ek or Ena?

Answer 11

1. Ek2. At rest cell is much more permeable to K

Question 12

What is indicated by the equilibrium potential?

Answer 12

Strength of the chemical driving force

Question 13

What does ouabain do?

Answer 13

Na/K ATPase inhibitor

Question 14

What is explained by the Goldman-Hodgkin-Katz equation?

Answer 14

1. Deals with how the permeability of the membrane to different ions affects the value of the membrane potential2. Can figure out how a change in ion concentration or ion permeability can change the membrane potential

Question 15

What happens to the membrane potential of the cell as the relative permeability of the membrane to an ion increases?

Answer 15

Moves closer to the equilibrium potential of that ion

Question 16

What happens to the membrane potential of a cell if the permeability of the membrane to K increases?

Answer 16

Moves closer to the equilibrium of K

Question 17

Why does a higher than normal extracellular concentration of K (hyperkalemia) depolarize a cell?

Answer 17

Not as much K has to leave cell before a depolarization occurs

Question 18

How does the Na/K pump maintain membrane gradient?

Answer 18

By counteracting constant Na and K leakage

Question 19

How does the Na/K pump regulate cell volume?

Answer 19

By pumping Na out of the cell it decreases the osmotic pressure in the cytoplasm and increases the osmotic pressure of the extracellular fluid

Question 20

Does calcium contribute to the resting membrane potential?

Answer 20

1. No2. Membrane is usually impermeable to calcium at rest3. Equilibrium potential of calcium is always a large positive number

Question 21

What is the definition of hyperpolarization?

Answer 21

Membrane becomes more negative inside

Question 22

What is the definition of depolarization?

Answer 22

Membrane becomes less negative inside

Question 23

What is the extracellular concentration of chloride ion?

Answer 23

Always higher than intracellular concentration