MCB 2210 Lecture Notes - Lecture 10: Calcium Atpase, Neurotransmitter, Symporter
3 Apr 2016
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Document Summary
Diffusion of ions gives rise to electrical potentials: as k+ ions flow out, cl- ions helped maintain charge balance are left behind. Cl- ions distribute themselves beneath the membrane, attracted to cations outside. K+ ion stop flowing out: only relatively few k+ ions acutally have to flow for there to be enough. No net currents are flowing with or without a concentration gradient. In real cells, vm is determined by the conductances of multiple ions: typically, resting cells have k+ conductance (gk) that"s 10x higher than the na+ and cl- conductances. Vm will be closest to the most permeable ion: in real cells, multiple conductances for different ions are active simultaneously. At any given vm, the driving force for an ion is its total electrochemical potential in mv. Vm reflects not equilibrium, but a steady state. There is no net ion flow: na+ current is equal and opposite to k+ current.
