Nernst
   z = # e-   R = gas constant 8.3 J/mol.K     T = absolute temp (273 + C)     F = Faraday 95,600 C/mol
  
 
   What about potassium ???   
K*      So if not passive how do ions get across a membrane ???



 
 
 
 
 
 
 
 
 
 
 
 
 
 
 






Nernst Potential for Potassium...   

    E (mv) = +/- 62 Lg10 [ Co ]
                                     [ Ci ]

                    [ Co ] =  1.0 mM  K  and  [ Ci ] = 7.0 mM

    
    E =  + 62  Lg10  1.0/7.0 

       =  + 62  Lg10   0.1428

       =  + 62  -(0.8453)

    E- 52.4 mV is the value of the calculated Nernst Potential

          since the measured bioelectric potential inside the cell is 
       + 10 mV then, K does NOT move passively across this
          membrane, and therefore
K must move ACTIVELY.
  



 K Nernst



         
        Walther Nernst

     Normal Electrolyte values of Cells   intracellular        
                                                                 Na            12   mmol/L
                                                                 K     140-150   mmol/L
                                                                 Cl               2   mmol/L

   extracellular
     Na      140  mmol/L
     K      3.5-5  mmol/L
     Cl        110  mmol/L

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