Ionic Distributions and Nernst Equation

Question 1

What creates a diffusion potential

Answer 1

concentration difference of an ion across a selectively permeable membrane

Question 2

what is another name for diffusion potential

Answer 2

membrane potential

Question 3

what way do molecules move in terms of energy

Answer 3

from high energy to low energy

Question 4

what kinds of forces create the energy that drive the movement of molecules

Answer 4

chemical
electrical
electrochemical

Question 5

when a molecule exists in a different concentration on either side of the membrane, there is what across the membrane

Answer 5

concentration gradient

Question 6

what symbol symbolizes the difference in concentration

Answer 6

∆C

Question 7

what is the name of the net force driving molecules down a concentration gradient

Answer 7

chemical driving force

Question 8

chemical driving force is directly proportional to what

Answer 8

concentration gradient

Question 9

the greater the concentration gradient, the greater the

Answer 9

force

Question 10

if there is more than one molecule across a membrane, describe their concentration gradients/driving force

Answer 10

they each have their own

Question 11

when molecules move from area of high concentration to an area of low it results in

Answer 11

release of energy

Question 12

when molecules release energy by going to lower concentration it is described as

Answer 12

going down concentration gradient

Question 13

ions, atoms or molecules w/ charge are affected by what force

Answer 13

electrical driving force

Question 14

if there is no concentration gradient but there are differently charged ions, there will still be

Answer 14

electrical driving force, still have movement of ions

Question 15

membrane potential results from

Answer 15

unequal distribution of charges across the membrane

Question 16

if anions and cations are balanced across the membrane, what is the membrane potential

Answer 16

0

Question 17

what is the unit the membrane potential is measured in

Answer 17

mV

Question 18

what does mV stand for

Answer 18

one thousandth of a volt (mili volt)

Question 19

what is membrane potential for most cells

Answer 19

-70 mV

Question 20

in resting cell, cations are attracted to

Answer 20

inside of cell

Question 21

in resting cell anions are attracted to

Answer 21

exterior of cell (outside)

Question 22

magnitude of electrical force depends on what

Answer 22

size of membrane potential

charge of the ion

Question 23

size of membrane potential & charge of ion determine what

Answer 23

magnitude of electrical force

Question 24

the greater the membrane potential or charge of the ion, the greater the

Answer 24

electrical driving force

Question 25

define the electrochemical driving force

Answer 25

total forces acting upon ions, combining chemical and electrical forces

Question 26

the net direction of electorchemical force =

Answer 26

sum of both forces

Question 27

the point at which the chemical and electrical forces (if they are going opposite direction) equal each other is the

Answer 27

equilibrium potential

Question 28

what does the equilibrium potential of an ion depend on

Answer 28

concentration gradient | valence (charge)

Question 29

Eion stands for

Answer 29

electrical potential difference

Question 30

The electrical potential difference (Eion) across the membrane required to oppose the concentration force exactly to prevent net diffusion of an ion is called the

Answer 30

Nernst or equilibrium potential for that ion.

Question 31

what is the nernst equation (write both versions)

Answer 31

``` delta u(x) = RTln[X]A + zF(EA - EB) [X]B ``` Eion (mV) = 60 log Co **THIS IS THE ONE TO KNOW z Ci

Question 32

what is the nernst equation used to determine

Answer 32

equilibrium potential of an ion

Question 33

What does R stand for in nernst equation

Answer 33

gas constant

Question 34

what does T stand for in nernst equation

Answer 34

absolute temperature

Question 35

what does XA stand for in nernst equation

Answer 35

concentration of ion X on side A

Question 36

What does XB stand for in nernst equation

Answer 36

concentration of ion X on side B

Question 37

what does z stand for in nernst equation

Answer 37

valence of ion

Question 38

What does F stand for in nernst equation

Answer 38

Faraday’s constant

Question 39

what does EA-EB stand for in nernst equation

Answer 39

electrical potential

Question 40

what does ∆u stand for in nernst equation

Answer 40

electrochemical potential difference (net force on ion)

Question 41

when chemical and electrical gradients are equal and opposite, ∆u=? it is said to be in

Answer 41

0 | electrochemical equilibrium!

Question 42

What does Co = in nernst equation?

Answer 42

concentration of ion outside of cell

Question 43

what does Ci = in nernst equation?

Answer 43

concentration of ion inside cell

Question 44

If the chemical and electrical forces are in opposite directions and the equilibrium potential > the membrane potential

Answer 44

the chemical force is larger and the combined electrochemical force is in the direction of the chemical force.

Question 45

If the chemical and electrical forces are in opposite directions and the membrane potential > equilibrium potential

Answer 45

the electrical force is larger and the electrochemical force is in the direction of the electrical driving force

Question 46

draw diffusion potential b/w nerve fiber A and B and explain

Answer 46

pg 3 ppt

Question 47

if we were at -94 at nerve fiber A (only permeable to potassium) with no net current, change the electrical driving force (not chemical) to -120 (making membrane potential more neg compared to outside) will there be net current if there is net current, what direction would potassium move

Answer 47

yes - b/c driving force is a different magnitude from chemical driving force inward potassium current b/c potassium is attracted at more negativity

Question 48

membrane potential is the

Answer 48

electrical driving force

Question 49

explain what you are looking at with nernst equation

Answer 49

if you have given chemical concentrations, are going to calculate the other driving force (electrical) and be equal opposite

Question 50

Vm =?

Answer 50

membrane potential (electrical)

Question 51

log of 100 is

Answer 51

2

Question 52

log of 10 is

Answer 52

1

Question 53

log of 1000 is

Answer 53

3

Question 54

. for any univalent ion if there is tenfold difference need what to oppose it

Answer 54

60 mV

Question 55

look at and understand pg 15

Answer 55

pg 15

Question 56

look at and understand pg 16

Answer 56

16

Question 57

hyperkaeilemia is what

Answer 57

outside of cell have higher potassium | increase in extracellular potassium

Question 58

why does potassium have bigger impact on membrane potential than sodium

Answer 58

Leak channels. Theres more leak potassium channels present so theres more movement of potassium and it has more of an impact on membrane potential.

Question 59

10 fold difference in univalent ion needs what as the other driving force

Answer 59

60 mV as other driving force

Question 60

change in driving force of potassium is going to change by factor of

Answer 60

60