Question

the concentration of sodium on the inside of the cell is 20 mm. the outside of the cell has a sodium concentration of 115 mm. which mechanism of ion uptake would best move sodium from the inside of the cell to the outside?
osmosis
diffusion
passive transport
active transport

Explanation:

Osmosis is the movement of water, not ions. Diffusion and passive transport move substances from high to low concentration. Here, sodium needs to move from low (20 mM inside) to high (115 mM outside) concentration, which requires energy - active transport is used for such movement against the concentration gradient.

Answer:

A. active transport