# How would I find the reversal potential for conductance

In summary, the reversal potential for conductance is the membrane potential at which the net flow of ions through a channel is zero. It is calculated using the Nernst equation and determines the direction of ion flow through a membrane channel. It can change depending on the conditions of the cell and is directly related to the membrane potential.
I know the following
ion/inside cell/outside cell
Cl- 5mM 150 mM
K+ 130mM 5mM
Na+ 20mM 140mM
Ca2+ 10^-4mM 2mM

How would I find the reversal potential for conductance equally permeable to sodium and potassium?
How do I find the reversal potential for a conductance equally permeable to sodium, potassium, and chlorine?

To find the reversal potential for conductance, you will need to use the Goldman-Hodgkin-Katz equation. This equation takes into account the relative permeability and concentrations of each ion to determine the overall reversal potential. It is given by:

Erev = (RT/zF) ln((PNa+[Na+]o + PK+[K+]o + PCl-[Cl-]o)/(PNa+[Na+]i + PK+[K+]i + PCl-[Cl-]i))

where R is the gas constant, T is the temperature in Kelvin, z is the valence of the ion, F is the Faraday constant, P is the relative permeability of the ion, and [ion]o and [ion]i are the concentrations of the ion outside and inside the cell, respectively.

For the first question, where the conductance is equally permeable to sodium and potassium, you will need to set PNa and PK to be equal in the equation. This will simplify the equation to:

Erev = (RT/zF) ln((P+[Na+]o + P+[K+]o)/(P+[Na+]i + P+[K+]i))

where P+ is the permeability of both sodium and potassium. You can then plug in the given concentrations for each ion and solve for Erev.

For the second question, where the conductance is equally permeable to sodium, potassium, and chlorine, you will need to set PNa, PK, and PCl to be equal in the equation. This will simplify the equation to:

Erev = (RT/zF) ln((P+[Na+]o + P+[K+]o + P-[Cl-]o)/(P+[Na+]i + P+[K+]i + P-[Cl-]i))

where P+ is the permeability of sodium and potassium, and P- is the permeability of chlorine. You can then plug in the given concentrations for each ion and solve for Erev.

It is important to note that the Goldman-Hodgkin-Katz equation assumes that the membrane is only permeable to these three ions and that there are no other factors affecting the membrane potential. Additionally, the equation assumes that the membrane is at equilibrium, meaning that there is no net movement of ions across the membrane. If these assumptions do not hold, the calculated reversal potential may not accurately reflect the true potential.

## 1. What is the reversal potential for conductance?

The reversal potential for conductance is the membrane potential at which the net flow of ions through a channel is zero. This means that the amount of ions moving into the cell is equal to the amount of ions moving out of the cell.

## 2. How is the reversal potential for conductance calculated?

The reversal potential for conductance can be calculated using the Nernst equation, which takes into account the concentrations of ions inside and outside of the cell, as well as the valence of the ions and the temperature.

## 3. Why is the reversal potential for conductance important?

The reversal potential for conductance is important because it determines the direction of ion flow through a membrane channel. If the membrane potential is higher than the reversal potential, the ions will move into the cell; if it is lower, the ions will move out of the cell. This allows for precise control of ion flow and is crucial for proper cellular function.

## 4. Can the reversal potential for conductance change?

Yes, the reversal potential for conductance can change depending on the conditions of the cell. Factors such as changes in ion concentrations, temperature, or the presence of other molecules can affect the membrane potential and therefore alter the reversal potential.

## 5. What is the relationship between the reversal potential for conductance and membrane potential?

The reversal potential for conductance is directly related to the membrane potential. As the membrane potential changes, the reversal potential also changes. This is because the reversal potential is the point at which the membrane potential is equal to the equilibrium potential for the specific ion, and the equilibrium potential changes with changes in membrane potential.

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