5.5 Osmosis
First review @October 16, 2023
Practise Q's Done
diffusion of water across a partially permeable membrane down a water potential
gradient
Water potential
Solute— substance dissolved in a solvent (e.g. water ) to form a solution
Concentration— measure of how much solute is present in a certain volume of aqueous
solution
Water potential (kPa)— the pressure exerted by water molecules on a container/
membrane as they collide with them, symbol is psi
Pure water has a water potential of 0 kPa at RTP which is the highest possible water
potential value, presence of solute in water lowers the water potential below 0
The more concentrated the solution, the lower the water potential
when solutions with different water potentials are separated by a partially permeable
membrane, water molecules are free to move between solutions but the solutes usually
don’t
net movement of water molecules from area of high water potential to low water
potential until equilibrium is reached
Effects of osmosis and plant animal cells
diffusion of water into a solution results in an increase in volume of solution
in a closed system this results in an increase in pressure e.g. inside a cell—
hydrostatic pressure (kPa) relatively large and can be damaging to cells
animal cells
if an animal cell is place in a solution with a higher water potential than that of the
cytoplasm, water will move into the cell via osmosis and increase the hydrostatic
pressure within the cell
5.5 Osmosis 1
First review @October 16, 2023
Practise Q's Done
diffusion of water across a partially permeable membrane down a water potential
gradient
Water potential
Solute— substance dissolved in a solvent (e.g. water ) to form a solution
Concentration— measure of how much solute is present in a certain volume of aqueous
solution
Water potential (kPa)— the pressure exerted by water molecules on a container/
membrane as they collide with them, symbol is psi
Pure water has a water potential of 0 kPa at RTP which is the highest possible water
potential value, presence of solute in water lowers the water potential below 0
The more concentrated the solution, the lower the water potential
when solutions with different water potentials are separated by a partially permeable
membrane, water molecules are free to move between solutions but the solutes usually
don’t
net movement of water molecules from area of high water potential to low water
potential until equilibrium is reached
Effects of osmosis and plant animal cells
diffusion of water into a solution results in an increase in volume of solution
in a closed system this results in an increase in pressure e.g. inside a cell—
hydrostatic pressure (kPa) relatively large and can be damaging to cells
animal cells
if an animal cell is place in a solution with a higher water potential than that of the
cytoplasm, water will move into the cell via osmosis and increase the hydrostatic
pressure within the cell
5.5 Osmosis 1
