Lecture 5 Flashcards
What is the charge of inside the cell membrane at resting potential?
slightly negative with respect to outside
Voltage difference across the membrane
membrane potential
Voltage difference across the membrane in excitable cells
resting membrane potential
what is the resting membrane potential value of epithelial cell?
-50mV
What is the resting membrane potential value of excitable cells?
-70~-90mV
Which ion is more concentrated intracellularly. K or Na? And why?
K because sodium potassium ATPase
3sodium out 2 potassium in
How does the potential difference arise? 2 factors
Ionic gradient exist across cell membrane
Cells are selectively permeable to ion : more permeable to K than other ion
What does rate of transport through ion channel depend on?
Depends on frequency of channel opening and duration of opening
How is potassium electrical gradient formed?in terms of equilibrium potential for K?
When K channel open, potassium flows out of the cell with concentration gradient, but as K flows out intracellular becomes more negative, eventually drawing K back inside. Then eventually K flowing out will equal K flowing in due to electrical gradient which achieves equilibrium membrane potential for K.
Value of equilibrium potential for K
-83
Value of equilibrium potential for Na
+69
What is different in Nerst equation when calculating equailibrium potential for Cl
Ratio of concentration outside and inside is reversed: outside/inside (always for anion)
Usually it is inside/outside (for cation)
Value of equilibrium potential for Cl
-46
What is goldman hodgkin katz equation
Modified version of nenerst equation that takes account of all ions and their relative permeability
When is driving force =0?
When membrane potential = equilibrium potential for that ion?
