Lecture 4 Flashcards
(8 cards)
What does the Na/K ATPase pump establish and how does K combat it
It establishes the initial chemical gradient by forcing K+ in and Na+ down its gradient (example of an antiport). To combat being moved against its concentration gradient, K+ leaves through channels taking positive charge out of the cell. Creating the Negative charge in the cell
What happens after sustained combat from K+
The voltage difference increases making it more negative and therefore creating an electrical gradient dragging K+ BACK into the cell. This will continue if uninterrupted until the movement of K+ out matches the flow of K+ in. The transmembrane voltage this occurs at is referred to as the K+ equilibrium potential, as its in electrochemical equilibrium
what is the equilibrium constant equation for K+ and what conditions would be needed to reach it
Ek= 61/1 x log10 x (4)/(140) or more simply = 61 x log10 x 0.028
Leaving us with -94mV, to reach this the cell would need to be permeable to only K+
What is the equilibrium constant equation for Na+ and what conditions would be needed to reach this
Ek = 61/1 x log10 x (140)/(12) or more simply 61 x log10 x 11.7 =+65mV
to reach this condition the cell would need to be permeable to only Na+
What happens when you combine the permeabilities of Na+ and K+ in a cell, like for example when at RMP
You would get a transmembrane voltage of -86mV, the cell would be highly permeable to K+ and slightly permeable for Na+ which is normal conditions of a cell
What is the rough RMP for nerve cells
-90 to -50mV
Describe a cell in a steady state
Electrostatic and chemical forces for Potassium movement are equal and opposite, so there is no net gain or net loss of K.
The cell is relatively impermeable to Sodium, so there is no net gain or net loss of Na
What type of channel when activated can cause another type of channel to open
When active a ligand/chemical gated channel can indirectly open a voltage gated channel
