BIOLOGY - OSMOSIS

Movement of water molecules across a partially permeable membrane from an area of high water potential to an area of low water potential

Tendency of water molecules to move into or out of a cell or solution

Kilopascals (kPa)

Large number of water molecules that are free to move

Pure water

Solute's contribution to the water potential

Negative as it always reduces water potential

When water enters a plant cell it expands the vacuole and pushed the cytoplasm against the cell wall. Pressure then builds up and makes cell Turgid

They don't gain or lose water as water moves in and out at the same rate.

Water moves into the cell which causes it to expand and could lyse

Same amount of water enters the cell as moved out of it, so cell is not damaged

Water leaves the cell and causes it to shrink

Cell membrane pulls away from the cell wall

Animal cell - Cytolysed, Plant cell - Turgid

Animal cell - normal, Plant cell - Flaccid

Animal cell - crenated, Plant cell - Plasmolyzed

50% of the cells are plasmolysed

Increase the rate at which water can enter/leave the cell without allowing other molecules to escape/enter