B4d-diffusion and osmosis Flashcards
What is diffusion?
The net movement of particles from an area of higher concentration to an area of lower concentration
What is diffusion a consequence of?
The random movement of individual particles
What do cell membranes do in diffusion?
- They let molecules in and out
- only small molecules can diffuse through
What is the rate of diffusion increased by?
Shorter distance
Greater concentration difference(gradient)
Greater surface area
How does a short distance affect the rate?
Substances diffuse quicker when they dont have to move as far
How does concentration gradient affect the rate?
- Substances diffuse faster if there is a bigger difference
- more on one side means more to move across
How does surface area affect the rate?
- More surface area means more room for molecules to move across
- faster they can get to one side
What is osmosis?
The net movement of water molecules across a partially permeable membrane from a region of higher water concentration to a region of lower water concentration
What does partially permeable mean?
A membrane with very small holes in it
What does the plant cell wall provide?
Support
How does turgor pressure help support the plant tissues?
Contents of cell push against the inelastic cell wall
Why does a plant wilt because of lack of water?
The cells start to lose water and so lose their turgor pressure
What is flaccid?
When a cell loses turgor pressure
What is plasmolysed?
When the cytoplasm inside the cell shrinks and the membrane pulls away from the cell wall due to lack of water
What is turgid?
Plump and swolllen
Where does water move in and out in animal cells?
Through the cell membrane
What is lysis?
When an animal cell takes in tok much water and it bursts
What is crenation?
When an animal cell loses too much water and it gets shrivelled up
Why are animal cells affected by changes in the amount of water?
They have no cell wall so they have to make sure the amount of water in their cells is constant
