Equilibrium Potentials II Answer 6

• On the inside, there are $400\ \text{mM} + 50\ \text{mM}$ of positive charge $= 450\ \text{mM}$, and there are $52\ \text{mM} + 385\ \text{mM}$ of negative charge $= 437\ \text{mM}$; therefore, to maintain electroneurtrality, there must be $13\ \text{mM}$ of negative charges that are unaccounted for on the inside of the cell. These may be other ion species, charged proteins, or something else.
• On the outside, there are $20\ \text{mM} + 440\ \text{mM}$ of positive charge $= 460\ \text{mM}$, and there are $560\ \text{mM}$ of negative charge; this implies there are $100\ \text{mM}$ of positive charges that are unaccounted for outside the cell to maintain electroneutrality. Again, these could be other ion species, like magnesium or calcium.