osmosis

Osmosis definition

Movement of water molecules from a higher water potential to a lower water potential through a selectively permeable membrane

unit for water potential

greek letter psi (sword shape)

kPa

how is water potential created

pressure created by water molecules

what water potential does pure water have under standard conditions?

zero

what will the addition of solute do to water potential

• lower water potential

• more negative water potential as more concentrated

where will water move to

region of less negative to more negative water potential

how to experimentally find water potential of cells

place in series of solutions of different water potentials

what is the random motion of the solute and water molecules due to

kinetic energy

what happens when the water potentials on either side of the membrane are equal

a dynamic equilibrium is reached and no net movement of water

can solute molecules pass through selectively permeable membrane

No

what is the highest value of water potential

zero

what do red blood cells contain

variety of solutes dissolved in their cytoplasm

what happens when RBC is placed in pure water and why

• water enters by osmosis

• thin cell membrane so will break

• cell bursts and will release its contents

what do they do to prevent this from happening

live in a liquid which has same water potential (blood plasma)

what happens if rbc looses water

shrinks and will have more concentrated haemoglobin so will have a darker red colour

3 components of plant cell

• protoplast

• central vacuole

• cellulose cell wall

what are plant cells unable to do?

Control composition of fluid around cell

what happens to plant cells unable when water is absorbed

• protoplast swells and pushes against cell wall

• pressure build up

• turgid

what happens in incipitent plasmolysis

the protoplast no longer pushes against cell wall

what happens during plasmolysis

the protoplast pulls away from cell wall