The negative charge that found inside the plasma membrane is created by movement of potassium ions.
Explanation:
The concentration of the potassium ions is very high inside the cell but low outside the cell whereas the concentration of both Sodium and chloride ions is more outside the cell but less inside the cell. Inside of the cell plasma membrane is negatively charged in spite of having large positively charged potassium ion concentration due to the presence of organic anions in large amount and leaks of potassium ions.
These anions are the charged group of the proteins and other organic molecules. As the membrane is more permeable to the movement of potassium ions outside the cell, the comparative ratio of the concentration of organic anion to cation increases with the decreasing cations concentration and causes the membrane to have a negative charge on the inside.
