Membrane Potential (Contd....)

  • Cellular proteins, phosphate groups and other organic molecules are negatively charged at the intracellular pH.
  • These anions are said to be fixed as they cannot diffuse out of the cell.

  • As a result these fixed anions attract the positively charged ions from the extracellular fluid that can diffuse into the cell.
  • As the cell membrane is more permeable to potassium, potassium accumulates into the cell.
  • This accumulation continues until an equilibrium between the entry of potassium down the electrical gradient and the exit of potassium down its concnetration gradient, is established.
  • At the concentration of the potassium ion found in the body, the fixed anions are not totally neutralised once the equilibrium is established.
  • Thus a net negative charge exists inside the cell.