Osmosis 5.5 Flashcards
Water Potential
The pressure exerted by water as it collides with the container or membrane. It is measure in pascal but the symbol is psi which looks like a trident
Solute
The substance that is dissolved in the solvent to make a solution
Concentration
The amount of solute that is present in an aqueous solution.
What is the water potential of pure water
It will be 0kpa and is the maximum, all water potentials of solutions are negative
Osmosis
The net movement of water molecules from a high water potential (low concentration) to a low water potential ( high concentration)
What happens as water diffuses across the membrane?
If it’s in a closed system like a cell, then the hydrostatic pressure will increase which can be very damaging.
What happens if an animal cell is placed in a solution with higher water potential than itself?
The water potential is higher on the outside of the cell than the inside so the water molecules will diffuse down the concentration gradient and into the cell which will result in the water potential inside the cell increases. Sometimes, too much water moves in at one time which increases the hydrostatic pressure and because the cell has a thin cell membrane, it cannot withstand a lot of pressure so it will burst which is called cytolysis.
What happens if an animal cell is placed in a solution with lower water potential than itself?
The water will move outside of the cell to try and reach equilibrium which will reduce the hydrostatic pressure of the cell and result in it becoming crenated.
How does the body prevent cytolysis or crenation
It will have an aqueous solution around at all times to maintain an equal water potential on both sides and keep it isotonic. This is blood plasma in the body.
How do plants deal with osmosis?
They cannot control the amount of water potential like animals, so instead, they have a thick cell wall made of cellulose that can withstand a big in hydrostatic pressure.
What happens when a plant cell is placed in a solution with higher water potential than itself?
The water will move into the cell by osmosis which will increase the hydrostatic pressure and the contents inside the cell will push against the plant cell wall. The cell will become turgid
What happens when a plant cell is placed in a solution with lower water potential than itself?
The water will move out of the plant cell by osmosis and the protoplast which is the inner layer will pull away from the cell wall and the cell will be plasmolysed.
Osmosis Investigation
You can investigate the effects of osmosis by using potatoes and placing them in solutions of varying solute concentration or water potentials. Then measure the difference in mass and then judge how osmosis has occured.
