equilibrium potentials lect 4

Question 1

definition of membrane potential (Vm)

Answer 1

electric potential energy stored across plasma membrane; voltage difference (V) across the membrane (m)

Question 2

what does “potential” in membrane potential refer to

Answer 2

ability to do work: this is possible because ions are far away from thier equilibrium potential

Question 3

what is a resting membrane potential

Answer 3

electrical potential difference across plasma membrane of cell that is NOT firing an action potential

Question 4

the seperation of a greater or lesser number of charges would have a larger membrane potential?

Answer 4

the magnitude of the potential depends on the number of opposite charges seperated; the greater the # of charges seperated the greater the potential

Question 5

What is the concentration of Na+ outside of the cell

Answer 5

150 mM

Question 6

what is the concentration of Na+ inside of the cell

Answer 6

15 mM

Question 7

what is the concentration of K+ inside of the cell

Answer 7

150 mM

Question 8

What is the concentration of K+ outside of the cell?

Answer 8

5 mM

Question 9

What is the concentration of Cl- inside vs outside of the cell

Answer 9

inside: 10mM
outside: 120mM

Question 10

ion channels are polypeptide chains that form what type of pores

Answer 10

water filled

Question 11

some ion channels have gates that are open in the absence of stimuli. What are these called?

Answer 11

background channels

Question 12

name the general types of ion channels

Answer 12

1) ungated channel 2) ligand-gated channel 3) voltage-gated channel

Question 13

when are voltage gated channels closed? when do they open?

Answer 13

at resting membrane potential, channel is closed. Membrane depolarization causes channel to open

Question 14

what is the chemical driving force

Answer 14

concentration gradient across the membrane

Question 15

what is the electrical driving force

Answer 15

seperation of charges cause an electrical gradient across the membrane

Question 16

equilibrium potential

Answer 16

diffusions potential (electrical force) that exactly balances or opposes the tendency for diffusion down the concentration gradient

Question 17

when is a particular ion in equilibrium?

Answer 17

when chemical and electrical driving forces are equal and opposite

Question 18

impearmeable negatively charged ions are found in the extracellular or intracellular environment?

Answer 18

intracellular

Question 19

is K+ or Na+ more permeable? Why?

Answer 19

K+; the cell has many more channels open for passive K+ traffic than for passive Na+ traffic

Question 20

at resting potential, the membrane is about how many time more permeable to K+ than Na+?

Answer 20

50-75

Question 21

what does the nernst equation calculate

Answer 21

calculate the equilibrium potential for AN ion at a given concentration difference across the membrane (Assuming membrane is permeable to ion)

Question 22

what is the nernst equation

Answer 22

Eion= (60/z) log ({ion}out/{ion}in) z= ionic valance of ion (charge +/-)

Question 23

Log 1000 =
Log 100 =
Log 10 =

Answer 23

3; 2; 1

Question 24

Log 1 =

Answer 24

0

Question 25

Log 0.1 =
Log 0.01 =
Log 0.001 =

Answer 25

-1; -2; -3

Question 26

what would resting Vm be for a cell to a certain compound (eg: KCl) if cell membrane is impermeable for both ions

Answer 26

0mV

* the only ions that contribute to Vm are those the membrane is permeable to

Question 27

all living cells have some resting membrane potential, but what two types of cells have the ability to produce rapid, transient changes in their membrane potential when excited

Answer 27

nerve and muscle cells

Question 28

what is the numerical value for the resting membrane potential

Answer 28

-70 mv

Question 29

what is the value of resting potential for K+ and Na+; which has a greater influence on Resting membrane potential

Answer 29

EK+ = -90 mV; ENa+ = +65 mV therefore K+ has a greater influence on RMP