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
- 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
- At the concentration of the
potassium ion found in the body, the fixed anions
are not totally neutralised once the equilibrium
- Thus a net negative charge exists
inside the cell.