Osmosis and Tonicity

What is Osmosis?

Osmosis is the movement of water from one place to another through a semi-permeable membrane, in an attempt to equalize the concentration. It moves from a place where there is more water to a place with less water to make things even.

This process is important because it moves materials and nutrients in/out of the cell, provides evidence of how different water levels become affected by gravity and forced to stop, even if the concentrations are not even, and helps stomata in plants open and close. Osmosis is also crucial to the human body as it helps us sweat, produce urine, maintain fluid balance, and so much more!

What is Tonicity?

Tonicity is the ability of a solution surrounding a cell to cause that cell to gain or lose water. Relative solute concentrations of two environments become separated by a semi-permeable membrane.

Hypertonic, Hypotonic, and Isotonic Solutions

Hypertonic Solution: A solution that has a higher concentration of solutes than the inside of a cell. Water moves out of the cell and into the solution, causing the cell to shrink.

EXAMPLE OF A HYPERTONIC SOLUTION: Syrup

Hypotonic Solution: A solution that has a lower concentration of solutes (salt or sugar) than the inside of a cell. Water moves into the cell, causing it to swell and potentially burst.

EXAMPLE OF A HYPOTONIC SOLUTION: Distilled water

Isotonic Solution: A solution that has the same concentration of solutes as the inside of a cell. Water moves in and out equally, so the cell remains the same size.

EXAMPLE OF A ISOTONIC SOLUTION: Saline solution