diffusion and osmosis. passive transport passive transport- movement of molecules across a cell...

Diffusion and Osmosis

Passive TransportPassive transport- movement of molecules

across a cell membrane without energy inputRefresh:

SoluteObject being dissolved

SolventObject doing the dissolving

DiffusionDiffusion: movement of molecules from areas of

high concentration to areas of low concentrationConcentration: number of molecules of a

substance in a given volumeConcentration gradient: difference of

concentration of a substance from one location to another

OsmosisOsmosis: Diffusion of water

Water moves across a semipermeable membrane from an area of high water concentration to an area of low water concentration

Types of SolutionsIsotonic: cell has same concentration of

dissolved particles as cellWater moves into and out of cell at equal rates

and cell size remains constant

Types of Solutions Cont.Hypertonic: Solution has a higher concentration

of dissolved particles than a cellWater concentration is higher in cell than outside

Water flows out of cell, cell shrivels

Types of Solutions Cont.Hypotonic: solution has lower concentration of

dissolved particles than a cellWater concentration is higher outside cell than

inside cellWater flows into the cell, cell swells

Cell may burst, this is called lysed

Plant CellsPlant cells prefer a hypotonic solution

Cell wall provides more support and are less likely to lyse

Plant cells at isotonic solutions are flaccidPlant cells at hypertonic solutions under-go plasmolysis

The cytoplasm and plasma membrane begin to pull away from the cell wall

Plant cell swells to point where it exerts a backward pressure, called turgor pressure This pressure prevents further uptake of water