Electrochemistry Flashcards
By the law of electroneutrality, if the intracellular conc. of + charges is 6 mM what should the conc. of - charge be?
6 mM
What does it mean to be at an electrochemical equilibrium state?
Force due to charge separation = force due to conc. gradient
What is the intracellular concentration of K+ in a normal cell?
120 mM
What is the extracellular concentration of K+ in a normal cell?
4 mM
What is the nernst equation?
v = RT/zF ln (Cout/Cin)
v = potential R= const. F = const. T = temp. z = signed charge of ion C = concentration
When using the nernst equation what does solving for v tell you?
The point at which EP = CP
What does decreasing the conc. gradient of potassium do?
reduces the voltage across the cell
What if Kin = Kout?
no membrane potential
In a normal cell the intracellular conc. of potassium is 120 mM, while extracellular is 4 mM. This generates a membrane potential of -88 mV. What is the chemical potential?
+88 mV, electrical and chemical potentials must be equal and opposite
What is the difference in Equilibrium and Steady State?
in both there is no net change in ion conc. but
-in steady state ATP is used to be sure certain concentrations are maintained
What would happen over time if Na+/K+ ATPase stopped working?
Na+ would leak in down its conc. gradient
K+ would leak out down its conc. gradient
What is the typical intracellular conc. of sodium?
14 mM
What is the typical extracellular conc. of sodium?
140 mM
T or F: different cell types have different Vm
True
What does the GHK equation take into account?
- concentration gradient across membrane
2. Relative permeability (P) of membrane to ions
What is the relative permeability (Pk) of potassium at rest?
95% - postassium = MUCH MORE PERMEABLE
What is the relative permeability (PNa) of sodium at rest?
5%
T or F: GHK and Nernst eqns. always tell you the charge on the inside relative to outside?
True
What does a resting potential of ~90 mV compared to 60 mV in normal cells suggest?
That K+ is probably even more permeable in cardiac tissue and that different tissues may have different permeabilities
What is the major determining factor of membrane potential?
Potassium
When is hyperkalemia observed?
kidney disease - lots of extracellular potassium
What is true of the cell in hyperkalemia?
it is depolarized (more positive)
What is true of hypokalemia?
Low extracellular conc. of K (cell = hyperpolarized)
When might hypokalemia be observed?
vomitting and disease over a long period