Question

What is tonicity?

Answer 1

Hint: The total passage of water over a semipermeable membrane from a decreased solute proportion to an increased solute level is known as osmosis. Many biological activities rely on osmosis, which occurs frequently at the same time as solute diffusion or transport.

Complete answer
Tonicity refers to an extracellular solution's capacity to induce water to migrate into or out of a cell via osmosis. Tonicity considers both relative solute concentrations and the porosity of the plasma membrane to those solutes.
To understand whether a solution will allow water to move into or out of a cell, three terminologies are used: hypertonic, hypotonic, and isotonic.
If the amount of solute in a solution is higher than that inside the cell, and the solutes cannot permeate the membrane, the solution is hypertonic to the cell.
The solution is hypotonic to the cell if the solute concentration outside the cell is lesser than inside the cell and the solutes cannot permeate the membrane.
When a cell is under an isotonic solution, there is no net movement of water inside or outside, and the capacity of the cell remains constant. The solution is isotonic to the cell if the concentration of the solute exterior to the cell is similar to the interior of the cell and the solutes cannot permeate the membrane.

Note:
When a cell is immersed in a hypertonic solution, water escapes and the cell diminishes. There is no net water movement in an isotonic environment, hence the cell size does not change. Water will enter a cell when it is placed in a hypotonic environment, causing it to inflate.