B2.1.2 Osmosis Flashcards
Define Osmosis
Osmosis is the movement of water particles from a high water potential to a lower water potential down the concentration gradient
What is water potential?
The concentration of free water molecules
The more concentrated a solution becomes…
The lower the water potential
The greater the distance in water potential…
The greater the rate of osmosis
Why does pure water have the highest water potential?
As is has the lowest concentration meaning more water molecules are free to move around
Explain why cell membranes are described as selectively permeable.
As it allows specific molecules to pass through it
How do plant cells become turgid?
When placed in a solution with a lower concentration than the contents of the cell, the cell takes in water by osmosis, increasing the turgour pressure therefore making the cell turgid
What happens to a plant cell when the surroundings have the same concentration as it’s contents?
There is no net movement of water.
The cell remains the same
What happens to a plant cell when placed in a more concentrated solution (lower water potential) than it’s contents? (5)
Loses water by osmosis
The turgor pressure falls
The cell becomes flaccid
Eventually, cell contents collapse away from the cell wall
This is called a plasmolysed cell
What happens to animal cell when placed in a solution that is less concentrated (higher water potential) than it’s contents?
Takes up water via osmosis
Swells, may burst
This is called lysis
What happens to animal cell placed in solution with same concentration as it’s contents?
No net movement of water
The cell remains the same
What happens to animal cell when placed in solution with higher concentration (lower water potential) than it’s contents?
Loses water by osmosis
The cell becomes cremated (crinkles)
Explain why glucose is not able to enter a cell through the partially permeable membrane:
A glucose molecule is too large to pass through a cell membrane via simple diffusion.
Instead, cells assist glucose diffusion through facilitated diffusion and two types of active transport.
Explain why a person would get dehydrated if they drank salty water:
