PSL300H1 Lecture Notes - Resting Potential, Semipermeable Membrane, Action Potential
Document Summary
An enzyme ion pump (e. g. atpase) must work to create a concentration gradient of ion species across the cell membrane. Semi-permeable membrane allows one ion species to diffuse across more than others. Diffusion of that ion species down its concentration gradient creates electrical gradient. Na+/k+ dependent atpase is an enzyme that moves na+ out of and k+ into cell. For each atp molecule broken down, 3 na+ ions are pumped out and 2 k+ pumped in. Na/k inequality -> potential difference of -10mv (inside of membrane with respect to the outside. "resting" membrane is most permeable to k+ ion. K+ diffuses out of cell, down concentration gradient, via "2-pore family" of k+ channels. Cations accumulate outside membrane, leaving a net negativity inside membrane. Anions (proteins) stuck inside cell repels other anions outside. Diffuse (through the 2-pore k channel) out until the point of electrostatic repulsion.
