B1.3.2 Osmosis Flashcards
The passive movement of water from an area of high water potential to an area of low water potential through a selectively permeable membrane is…
OSMOSIS
Osmosis involves the movement of
water ONLY
By adding more solute the a solution how does this affect the water potential
it lowers the WP - becomes more negative
Why does pure water have a higher water potential than a solution of sugar
there are more ‘free’ water particles in pure water
A potato has a WP of -200kPa was placed in pure water WP 0kPa, what happens?
Water ENTERS the potato by osmosis (water moved from a high WP to a lower WP)
water potential is represented by
psi (greek letter)
water potential is measured in units of pressure which are
kPa
Pure water has a WP of
0kPa
How can you determine the the WP of a potato
place potato in a series of solutions of different WP. Where there is no net gain of water by the potato is the WP of the potato.
What happens if a red blood cell is placed in pure water
it swells and bursts - water enters the cell
What happens if a red blood cell is placed in strong sugar solution
It shrinks - water leaves the cell
What happens if a plant cell is placed in pure water
It swells - water enters the cell - it becomes turgid
What happens if a plant cell is placed in strong salt solution
water leaves the cell - it shrinks - it plasmolysed
What is meant by selectively permeable
Membrane only allows certain molecules through; it is only permeable to water and other small molecules `
During an osmosis practical, how and why do you dry the potato chips?
with a paper towel. To remove surface water - This would add to the mass - which we do not want
