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Description of k+ in live cells, using nerst equation
- 1. Description of K+ in live cells, using nernst equation Niraj Kumar AE13B053 Pratham Bhat AE13B055
- 2. Live cell In a live cell a potential difference exists across the cell membrane due to ❖ Difference in concentration of ions ❖ Selective permeability of membrane.
- 3. Live cell Concentration of K+ inside cell = 150 mM Concentration of K+ outside cell = 5 mM Concentration of Na+ outside cell = 142 mM Concentration of Na+ inside cell = 10 mM Concentration of Cl- outside cell = 103 mM Concentration of Cl- inside cell = 4 mM
- 4. Concentration of K+ ions inside the cell is higher than outside This concentration difference is maintained using Na-K Pump, different voltage gated channels and leak channels.
- 5. Due to the concentration gradient, the K+ ions diffuse out of the cell through the different ion channels present in the cell membrane. This leads to accumulation of net negative charge inside the cell.
- 6. In this way an electric field is generated, which tries to get the K+ ions to diffuse into the cell. Now there are two opposing forces acting on the K+ ion. The chemical gradient drives the K+ ion out of the cell The electric gradient causes the K+ ions to diffuse into the cell. For some value of potential difference,these two forces are balanced . This is the membrane potential due to K+ ion
- 8. Nernst Equation Where R : Universal gas constant = 8.314 JK-1 mol-1 T : Temperature in Kelvin (K) Z : Charge on the ion F : Faraday's constant = 96500 coulombs mol -1
- 9. Contribution of K+ to membrane potential Concentration of K+ inside cell = [Ki +] = 155 mM Concentration of K+ outside cell = [Ko +] = 5 mM Substituting the above values, we get V ~ -92 mV
- 10. Membrane potential Membrane potential is weighted sum of potential of individual ions. Weights for each ion depends on permeability of that ion through the membrane.
- 11. So, we get membrane potential closer to the potential due to the ion to which the membrane is most permeable,which is K+ in this case
- 12. Thank You!
Editor's Notes
- Typical Concentrations
- In this presentation we are going on K+ ions As shown in the previous slide Concentration of K+ on the inside is more
- These channels only allow K+ ions to pass through.
- In this way an electric field is generated, which tries to get the K+ ions to diffuse into the cell
- Now there are two opposing forces acting on the K+ ion. The chemical gradient drives the K+ ion out of the cell and the electric gradient causes the K+ ions to diffuse into the cell.
- Here we took concentration of ions same as initial given because even after equilibrium concentration of k+ is very high. It is 10^20 ions per liter so small exchange of ions doesn’t affect concentration much.