Osmosis Flashcards
What is osmosis?
Osmosis is the diffusion of water molecules across a partially permeable membrane from an area of high water potential to an area of low water potential down a water potential gradient
What is a ‘solution’?
Mixtures made up of a solute dissolved in a solvent
What is a ‘solute’?
Something that is dissolved in a solvent
What is a ‘solvent’?
Liquid that a solute dissolves in
What is meant by ‘water potential’?
The pressure that is exerted by water molecules on the membrane surrounding a solution
What is water potential measured in?
KiloPascals (kPa)
What is meant by ‘high water potential’ in a solution?
The solution has a high water concentration so not much solute dissolved in it
What is meant by ‘low water potential’ in a solution?
The solution has a low water concentration so has lots of solute dissolved in it
What are the 3 types of solutions?
1) Hypotonic
2) Isotonic
3) Hypertonic
What is a hypotonic solution?
A solution that has a higher water potential than the cell
If a cell was placed in a hypotonic solution, what would happen?
Water molecules would move into the cell and it will swell and burst
- However plant cells don’t burst due to their cell wall
What is an isotonic solution?
A solution that has the same water potential as the cell
If a cell was placed in an isotonic solution, what would happen?
No net movement of water in or out of the cell and the cell remains the same size
What is a hypertonic solution?
A solution that has a lower water potential than the cell
If a cell was placed in a hypertonic solution, what would happen?
Water molecules move out of the cell and the cell will shrink and if the cell is a plant cell, it will also become plasmolysed
What are the 4 key factors that affect the rate of osmosis?
1) Temperature
2) Water potential gradient
3) Thickness of membrane
4) Surface area
How does higher temperatures affect the rate of osmosis?
At higher temperatures, water molecules have more kinetic energy and will diffuse faster
How does the water potential gradient affect the rate of osmosis?
The steeper the gradient, the faster rate of osmosis
How does the thickness of the membrane affect the rate of osmosis?
If a cell membrane is thin, water molecules will travel shorter distances and will diffuse faster
How does surface area affect the rate of osmosis?
Larger surface area allows for more water molecules to cross the membrane at once, which speeds up the rate of osmosis
