4.3 - Osmosis Flashcards
The definition of water potential The process of osmosis Factors affecting the rate of osmosis (20 cards)
What is a solution?
Mixture of solute dissolved in a solvent
What is water potential (Ψ)?
Pressure exerted by water molecules on a membrane surrounding a solution
What units is water potential measured in?
kiloPascals (kPa)
What does high water potential mean?
High water concentration (not very much solute dissolved in it)
What does low water potential mean?
Low water concentration (lots of solute dissolved in it)
What is the water potential of pure water?
0 kPa
What is osmosis?
Diffusion of water across a partially permeable membrane from an area of higher water potential to an area of lower water potential
What type of molecules can diffuse through the cell membrane?
OSMOSIS
Water molecules
What happens during osmosis?
Water moves down a water potential gradient to equilibrium
What happens to animal cells in a hypotonic solution?
3 steps
- Higher water potential than the cell.
- Water molecules move into the cell.
- The cell swells and bursts.
What happens to animal cells in an isotonic solution?
- Same water potential as the cell.
- There is no net movement of water into or out of the cell.
- The cell stays the same size.
What happens to animal cells in a hypertonic solution?
- Lower water potential than the cell.
- Water molecules move out of the cell.
- The cell shrinks.
What happens to plant cells in a hypotonic solution?
3 key steps
- Higher water potential than the cell.
- Water molecules move into the cell.
- The cell swells and becomes turgid.
What happens to plant cells in an isotonic solution?
3 key steps
- Same water potential as the cell.
- There is no net movement of water into or out of the cell.
- The cell stays the same size.
What happens to plant cells in a hypertonic solution?
3 key steps
- Lower water potential than the cell.
- Water molecules move out of the cell.
- The cell shrinks and becomes plasmolysed.
What factors affect the rate of osmosis?
4 Key factors
- Temperature - At higher temperatures, water molecules have more kinetic energy and diffuse faster.
- Water potential gradient - The steeper the gradient, the faster the rate of osmosis.
- Thickness of membrane - Water molecules travel shorter distances through thin exchange surfaces, so diffuse faster.
- Surface area - Larger surface areas mean more water molecules can cross the membrane at once, making osmosis faster.
How does temperature affect osmosis?
water molecules have more kinetic energy and diffuse faster.
How does water potential gradient affect osmosis?
steeper the gradient, the faster the rate of osmosis
How does membrane thickness affect osmosis?
travel shorter distances through thin exchange surfaces, so diffuse faster.
How does surface area affect osmosis?
Larger surface areas mean more water molecules can cross the membrane at once, making osmosis faster.
