Which of the following is most True for movement of a Na+ ion across the plasma

Question

Which of the following is most True for movement of a Na+ ion across the plasma membrane of a living cell?

A.Movement of Na+ from inside to outside a cell is up its molecular concentration gradient and requires input of energy B.Movement of Na+ from inside to outside a cell is up its electrical gradient and requires input of energy C.Movement of Na+ from outside to inside a cell is energetically favorable and yields energy D.A and B but not C E.A, B, and C Which of the following is most True for movement of a Na+ ion across the plasma membrane of a living cell?

A.Movement of Na+ from inside to outside a cell is up its molecular concentration gradient and requires input of energy B.Movement of Na+ from inside to outside a cell is up its electrical gradient and requires input of energy C.Movement of Na+ from outside to inside a cell is energetically favorable and yields energy D.A and B but not C E.A, B, and C
A.Movement of Na+ from inside to outside a cell is up its molecular concentration gradient and requires input of energy B.Movement of Na+ from inside to outside a cell is up its electrical gradient and requires input of energy C.Movement of Na+ from outside to inside a cell is energetically favorable and yields energy D.A and B but not C E.A, B, and C A.Movement of Na+ from inside to outside a cell is up its molecular concentration gradient and requires input of energy B.Movement of Na+ from inside to outside a cell is up its electrical gradient and requires input of energy C.Movement of Na+ from outside to inside a cell is energetically favorable and yields energy D.A and B but not C E.A, B, and C

Explanation / Answer

Answer is E. Statement A, B, and C are correct.

Concentration of Na+ inside the cell(10 mEq/L) is less than its concentration outside the cell(142 mEq/L). Therefore, the movement of Na+ across the cell membrane against the concentration gradient(inside to outside) requires ATP.

Example: Na+ K+ ATPase.

Inside of the cell is negatively charged compared to outside of the cell. Therefore the movement of positive ions across the cell membrane from inside to outside the cell will require ATP as there is movement of Na+ ion against the electrical gradient.

Movement of Na+ from outside to inside a cell is energitically favorable and yields energy. This energy is released is usually used by the cell to transport other molecules against their concentration gradient along with sodium. This is known as secondary active transport. Example: sodium-glucose co-transport, Sodium co-transport of amino acids.

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