Question

You have a cation that has an equilibrium potential with a positive charge. Where is that ion more highly concentrated (Intracellular or extracellular)?

How do you know?

If an anion has a higher concentration outside the cell, what will be the charge of its equilibrium potential?

Explain your answer.

Answer 1

1.A cation is a positive charged ion.If the Cation has an equilibrium with a positive charge its is highly concentrated in extracellular. The Resting Membrane Potential of a cell is negative it attracts the positive charge inside the cell but to maintain the negativity of the Resting Membrane potential it do not allow the positive charges to enter inside the cell i.e, even though the cell attracts the positive charge it do not allow the ion to enter into the cell.

• For Example,In humans,we all know the concentration of sodium are higher outside the cell and the sodium ions are positively charged with positive equilibrium potential positive because the membrane of the cell is not permeable to sodium as its entry into cell increases positivity inside the cell
• Likewise,The Potassium is positive charged ion with negative Equilibrium the cell membrane is permeable to potassium because the ion potential is near to the resting cell membrane potential.so,the potassium freely move across the membrane and its concentration is higher inside the cell.
• This shows that The cation with positive equilibrium potential have concentration higher outside the cell (Extracellular)

2.An anion with Higher concentration outside the cell have equilibrium potential have positive Equilibrium because the charge Inside the cell is negative.we know that like charges repel each other.So, the anion is pushed to outside from the cell.As above said the concentration outside the cell is high then their equibrium potential becomes negative.

• For Example,the Chlorine is a negative charged ion with higher concentration outside the cell have Positive equilibrium Potential because the chloride ions present inside and outside the cell but more likely they are pushed to outside because of their like charges and to maintain concentration gradient.
• This shows that an Anion with Higher Conentration outside the cell have Positive Equilibrium Potential

We can also answer the above questions by using Nerst Equation, Equilibrium Potential = RT/zF log [(X)_out/(X)_in]

here R= Universal Gas Constant,T= Temperature in Kelvin,z= Valency,F=Faradic Constant,X_out= Ion concentration outside and X_in = Ion concentration inside