Lecture 13-15: Resting Membrane Potential

ions move in response to

1) chemical driving force (diffusion down concentration gradient) 2) electrical driving force (positive and negative charged ions on the intra and extra cellular membrane NO ATP used when going down the concentration and electrical gradient

charge separation across a membrane

charge difference is just across the membrane and not across the entire cellular solution. remainder of the fluid is electrically neutral where as the charges on the intracellular and extracellular sides of the membrane are attracted (or repulsed by each other)

macromolecular anions (A-)

high intracellular concentration of nucleic acids and proteins which carry a net negative ionic charge

permeability of ions

measure of how easily ions can move across the membrane

conductance

measure of how much charge can move across the membrane

hydrostatic pressure from osmosis

pressure exerted by water at equilibrium after osmosis due to the force of gravity. cells will burst or shrivel up due to osmotic pressure.

why doesn't movement due to electrical force cause a change in concentration?

the number of ions that have to cross the membrane to generate a resting membrane potential is small compared to the total number of ions in the bulk solution. bulk of the cellular solution is neutral

resting membrane potential (Vm)

voltage difference across the plasma membrane in millivolts when the cell is at rest cells have more negative charges inside at rest (more K+ inside the cell); cells have a resting membrane potential of around -70mV