Ionic Gradients Flashcards
Space charge neutrality
The number of cations in a given volume is equal to the number of anions.
Ions still diffuse across the membrane, but each K+ that crosses the membrane must be accompanied by a Cl− for space charge neutrality to be satisfied.
Donnan potential
Created by presence of negatively charged proteins inside the cell
The distribution of ion species between two ionic solutions separated by a semipermeable membrane or boundary
How does passive distribution lead to higher K+ concentration inside cells?
K+ Leak channels
Space-charge neutrality
Donnan potential
2PK channels
Two-pore potassium channels
Not voltage/ligand gated
TWIK-1 gene encodes
Lipid bilayer
Acts as capacitor with solutions on either side acting as conductors
What would the resting potential of membrane be with just K+?
-90mV
Why are chloride ions pumped out alongside Na+/K+ ATPase?
The pumping of Cl- ions out of the cell by the Na/K ATPase is important for maintaining both the ionic and electrical gradients across the cell membrane.
Why are calcium ions pumped out alongside Na+/K+ ATPase?
the Na/K ATPase does indirectly affect calcium levels by generating a membrane potential that drives the entry of Ca2+ ions into cells through voltage-gated calcium channels.
Signalling molecule that can cause cell death and change protein conformation
Why is the nernst equation important?
The equilibrium potential for any particular ion
Voltage where chemical and electrical forces come to equilibrium is determined by the concentration of ions on either side of the lipid.
Nernst Equation
Es = (RT/zF)ln([S]out/[S]in)
R = gas constant
z = valency of ion
s = particular ion
T = temp
F = faraday’s constant
R gas constant value
8.3 J/k x mol
Faraday’s constant
9.4 x 10^4 J/mol x V
Goldman-Hodgkin-Katz equation
Resting membrane potential = …
Open rectification
Preferential flow of ions in channel in one direction or another
Permeability constant of potassium
20
