Science
What is Osmosis?
Osmosis is the movement of water across a semipermeable membrane from a region of lower solute concentration to higher concentration, balancing the two sides. It's how cells take in and lose water.
See it, don’t just read it.
Watch a 2-minute lesson with voice + animation that explains osmosis.
Key things to understand
- 1Water moves toward the side with more dissolved solute, through a membrane that blocks the solute.
- 2It continues until concentrations balance or pressure stops it.
- 3It's vital in biology: roots absorb water, cells stay hydrated, kidneys filter blood.
- 4It's a passive process — no energy is required.
Frequently asked questions
- How is osmosis different from diffusion?
- Diffusion is the spread of any particles; osmosis is specifically water moving across a semipermeable membrane.
- Why do plant roots use osmosis?
- Soil water has fewer solutes than root cells, so water flows into the roots by osmosis.
- What happens to a cell in salty water?
- Water leaves the cell by osmosis toward the saltier outside, and the cell shrinks.