(a) If a cell has a higher water concentration than the surrounding medium, it will lose water through osmosis, causing the cell to shrink; this is called exosmosis.
(b) If a cell has a lower water concentration than the surrounding medium, it will gain water through osmosis, causing the cell to swell; this is called endosmosis.
(c) If a cell has an equal water concentration to its surrounding medium, there will be no net movement of water, and the cell will remain unchanged; this is called an isotonic condition.
Explanation: Water always moves from a region of higher concentration to a region of lower concentration, a process called osmosis.
Key points:
Hypertonic:
A cell with a higher water concentration than its surrounding medium is considered hypertonic.
Hypotonic:
A cell with a lower water concentration than its surrounding medium is considered hypotonic.
Isotonic:
A cell with an equal water concentration to its surrounding medium is considered isotonic.