Explain what is happening in this clip.

Objective:Objective: You will be able You will be able to explain how molecules to explain how molecules

move across a semi-move across a semi-permeable membrane due to permeable membrane due to

a concentration gradient.a concentration gradient.

Diffusion & OsmosisDiffusion & Osmosis

DiffusionDiffusion

The movement of molecules The movement of molecules from an area in which they from an area in which they

are highly concentrated to an are highly concentrated to an area in which they are less area in which they are less

concentrated. concentrated.

See an animation of See an animation of diffusion here:diffusion here:

http://lewis.eeb.uconn.eduhttp://lewis.eeb.uconn.edu/lewishome/applets/Diffusi/lewishome/applets/Diffusion/diffusion.htmlon/diffusion.html

How did the gummy bear How did the gummy bear lab illustrate diffusion? lab illustrate diffusion?

Explain or draw a diagramExplain or draw a diagram

OsmosisOsmosis

The diffusion of The diffusion of waterwater across across a selectively permeable a selectively permeable

membranemembrane..

Did the gummy bear lab Did the gummy bear lab illustrate diffusion or illustrate diffusion or

osmosis? osmosis? Explain your answerExplain your answer

OsmosisOsmosis   

Water moves from a high Water moves from a high concentration of water (less salt or concentration of water (less salt or

sugar dissolved in it) to a low sugar dissolved in it) to a low concentration of water (more salt or concentration of water (more salt or sugar dissolved in it).  This means sugar dissolved in it).  This means

that water would cross a selectively that water would cross a selectively permeable membrane from a dilute permeable membrane from a dilute solution (less dissolved in it) to a solution (less dissolved in it) to a

concentrated solution (more concentrated solution (more dissolved in it).dissolved in it).

http://www.usd.edu/~bgoodman/Osmos.htm

What happens when the What happens when the concentration of water differs on concentration of water differs on

both sides of a membrane?both sides of a membrane?

See an animation of See an animation of osmosis here:osmosis here:

http://lewis.eeb.uconn.eduhttp://lewis.eeb.uconn.edu/lewishome/applets/Osmos/lewishome/applets/Osmosis/osmosis.htmlis/osmosis.html

Animal cells in WATERAnimal cells in WATER In this picture a red blood In this picture a red blood

cell is put in a glass of cell is put in a glass of distilled water (all water distilled water (all water with no salt or sugar in it).  with no salt or sugar in it).  Because there is a higher Because there is a higher concentration of water concentration of water outside the cell, water outside the cell, water enters the cell by enters the cell by OSMOSISOSMOSIS.  In this case too .  In this case too much water enters and the much water enters and the cell swells to the point of cell swells to the point of bursting open.  In the end bursting open.  In the end pieces of cell membrane pieces of cell membrane are left in the water. are left in the water.

Normal Distilled water Salt water

Isotonic cells Hypotonic cellsHypertonic cells

Define selectively Define selectively permeable membrane permeable membrane

Selectively permeable membraneSelectively permeable membrane

A membrane that allows only A membrane that allows only certain materials to cross it certain materials to cross it

Materials pass through Materials pass through porespores in the membranein the membrane

For more information on For more information on diffusion & osmosis, click diffusion & osmosis, click

here:here:

http://edtech.clas.pdx.edu/osmosis_thttp://edtech.clas.pdx.edu/osmosis_tutorial/default.htmlutorial/default.html

Why are osmosis & Why are osmosis & diffusion important?diffusion important?

Why are osmosis & diffusion Why are osmosis & diffusion important?important?

All living things have certain requirements All living things have certain requirements they must satisfy in order to remain alive – they must satisfy in order to remain alive – maintain maintain homeostasishomeostasis

These include exchanging gases (usually These include exchanging gases (usually CO2 and O2), taking in water, minerals, CO2 and O2), taking in water, minerals, and food, and eliminating wastes. and food, and eliminating wastes.

These tasks happen at the cellular level.These tasks happen at the cellular level. Molecules move through the cell Molecules move through the cell

membrane by diffusionmembrane by diffusion

Why are osmosis & diffusion Why are osmosis & diffusion important?important?

All living things have certain All living things have certain requirements they must satisfy in requirements they must satisfy in order to remain alive. These include order to remain alive. These include exchanging gases (usually CO2 and exchanging gases (usually CO2 and O2), taking in water, minerals, and O2), taking in water, minerals, and food, and eliminating wastes. These food, and eliminating wastes. These tasks ultimately occur at the cellular tasks ultimately occur at the cellular level, and require that molecules level, and require that molecules move through the membrane that move through the membrane that surrounds the cell. surrounds the cell.

Why are osmosis & diffusion Why are osmosis & diffusion important?important?

This membrane is a complex This membrane is a complex structure that is responsible for structure that is responsible for separating the contents of the cell separating the contents of the cell from its surroundings, for controlling from its surroundings, for controlling the movement of materials into and the movement of materials into and out of the cell, and for interacting out of the cell, and for interacting with the environment surrounding with the environment surrounding the cell. the cell.