NUR968 Membrane Potentials & Action Potentials - Cell Signaling & Second Messenger Systems Test With Solution

NUR968 Membrane Potentials & Action
Potentials - Cell Signaling & Second Messenger
Systems Test With Solution


What is the membrane potential? - ANSWER Defined as the electrical
potential difference across a cell's plasma

How are ions classified? (2) - ANSWER 1. Cations (positively charged)

2. Anions (negatively charged)

Although all positive & negative charges establish membrane potential, what
are the 2 key players (ions)? - ANSWER 1. Sodium

2. Potassium

True or false: The net flux of ions is a continuous dynamic process (never
static) - ANSWER True

How much more permeable is the plasma membrane to potassium? -
ANSWER 100x more permeable

True or false: The Sodium Potassium ATPase Pump moves ions AGAINST
their concentration gradient - ANSWER True

The plasma membrane contains protein channels called "leak channels."
What do these do? - ANSWER They leak ions (they are always open)

Which ions are leaked is dependent on what 3 factors? - ANSWER 1. The
polarity of the electrical charge of the ion & the charge on either side of a
membrane

,2. The permeability or "selectability" (specificity) of the leak channels to an
ion

3. Concentration gradient on either side of the leak channel

With potassium & sodium, which ion has the greatest concentration INSIDE
the cell? What about OUTSIDE the cell? - ANSWER Inside = Potassium

Outside = Sodium

So, why is potassium (a cation) more likely to leak out of the cell? - ANSWER
Because of the permeability to potassium

-As potassium leaves, it takes with it a positive charge leaving the inside of
the cell "more negative". This negativity then pulls potassium back in

Recall from Module 1:

When the Sodium Potassium Pump runs, 3 Na+ move OUT; 2 K+ move IN.
What is happening inside/outside of the cell each time this happens? -
ANSWER The inside of the cell becomes more NEGATIVE & the outside
becomes more POSITIVE (Separation of Charges)

What is a key player in maintaining the concentration gradients?*** -
ANSWER Sodium Potassium Pump

-Overall, sodium is predominately on the outside of the cell

-Potassium is predominately kept on the inside

Nernst Equation

-Nobel prize in 1920

-Relates the __ __ to the electrical force

, -Electromagnetic force (EMF) __ diffusion despite the ion concentration
gradient

-EMF (mv) = +/- __log (Concentration inside/Concentration outside) -
ANSWER -Nobel prize in 1920

-Relates the MEMBRANE POTENTIAL to the electrical force

-Electromagnetic force (EMF) OPPOSES diffusion despite the ion
concentration gradient

-EMF (mv) = +/- 61log (Concentration inside/Concentration outside)

So what does the Nernst equation help us equate? - ANSWER Helps us
equate the potential created by separating ions across a membrane ("helps
us determine what the resting membrane potential is")

-Recall that electrical charges can oppose diffusion

So what is the Resting Membrane Potential (RMP)? - ANSWER The electrical
difference between the inside & the outside of the cell

What is potassium's concentration on the inside to the outside? - ANSWER
35 : 1

What is sodium's concentration on the inside to the outside? - ANSWER 0.1 :
1

True or false: If we took all of the ions on either side of the cell & ran them
through the Nernst equation & then added them up, we would theoretically
get the actual resting membrane potential - ANSWER True

Why is the Nernst Equation considered too simple or flawed? - ANSWER It
only takes into account two ions (sodium & potassium)