Why are cells more negative inside if K+ and Na+ are both positive??

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Why are cells more negative inside if K+ and Na+ are both positive??

In: Biology

3 Answers

Anonymous 0 Comments

Proteins tend to have a negative charge and the inside of cells are packed with protein. Also in nerve cells there is the sodium/potassium pump that moves out 3 potassium ions for every 2 sodium ions it allows in.

Anonymous 0 Comments

Firstly there are also lots of negative ions – chloride, bicarbonate, ammonium, phosphates and proteins which have negative charge to balance the positive ions – sodium, potassium, calcium, magnesium.

Secondly the levels of K+ and Na+ are strictly controlled by the cell membrane which won’t let them through except through special channels and the sodium/potassium pump system. This means there is a difference between the inside and outside, with more sodium outside than inside and more potassium inside than outside. This causes a gradient of charge (see Nernst and Goldman equations for non-5 year olds). The gradient means the inside is more negative than the outside by a really small amount (-60-90 millivolts depending on the cell).

This is only really important in cells like nerves and muscles which transmit electrical signals – a channel opens allowing lots of sodium to come in down its concentration and electrical gradients (ie from lots and positive to little and negative) which means a change in the gradient, that gets transmitted along the cell membrane. The cell then corrects the charge gradient by moving potassium then sodium with a special pump as pumps can work against the gradient.

Anonymous 0 Comments

Because they contain Cl- and HCO3- ions. The Cl- ion channel is voltage gated so it doesn’t open until a certain negative electric potential is met. So as the Na-K pump lowers the electric potential of the cell, the cell becomes negative until a certain point.