How does tonicity affect osmosis?

Osmosis refers to the movement of water across a semipermeable membrane from a low solute concentration area to a high solute concentration area. Tonicity determines whether osmosis pushes water into or out of a cell. It impacts the direction and the extent to which water moves by osmosis. 

When a cell is placed in a hypertonic solution (the solute concentration outside the cell is higher than that inside the cell), water flows out of the cell into the extracellular solution, and the cell loses volume and shrinks. 

When a cell is placed in a hypotonic solution (the solute concentration outside the cell is lower than that inside the cell), water flows from the extracellular solution into the cell, and the cell gains volume.

When a cell is placed in an isotonic solution (the solute concentration outside and inside the cell are the same), there will be no net flow of water into or out of the cell, and the cell’s volume remains unchanged.