Question

What do hypertonic, hypotonic, and isotonic mean?

Answer 1

It's an indication of the osmotic pressure (water potential of 2 solutions separated by a semi-permeable mebrane) of cells. Let's say we use the salt concentration in and outside the cell.

When the salt concentration inside the cell is greater than outside the cell, we have a hypotonic solution. The water can only move and will go to the side where the salt concentration is bigger in an attempt to equalize the concentration on both sides. So in a hypotonic solution, the water will go in the cell which will make the cells swell up.

When the salt concentration outside the cell is greater than inside the cell, we have a hypertonic solution. The wate wil go out of the cell and the cells will shrink.

And isotonic means that the concentrations inside and outside the cell are the same. So nothing happens.

A 0.9% NaCl (salt) solution is isotonic for blood cells.
A 2% NaCl solution is hypertonic for blood cells.
And under 0.9% is hypotonic for blood cells.

Answer 2

Thanks.