Diffusion and Osmosis Please take notes on page 71

The Cell Membrane Gatekeeper Regulates what comes in and out of the cell Are semi-permeable; allow certain molecules and ions in and out In both plant and animal cells

Cell Wall Found only in plant cells and bacteria cells Main function is support Have holes to allow stuff in and out

Diffusion The movement of molecules from an area of high concentration to an area of low concentration Molecules tend to “spread out” and equalize Requires no energy

Equilibrium When molecules are evenly spread throughout a space

Osmosis The diffusion of water across a membrane The cell membrane is selectively permeable and water is one of the lucky ones! Watch the animationanimation

Rule for Osmosis If the area outside the cell has more salt – then water will be sucked out of the cell

U - Tube

Cells In Different Solutions Isotonic Solutions “ISO" means the same Amount of dissolved material is the same inside and outside the cell –Animal cells do well in this type of solution

Hypo = less Hypotonic Solutions Cells without a cell wall will swell and may burst in this solution Cells with a cell wall will swell, but once firm the cell wall prevents any more water from entering the cell –Plant cells like this solution!

Hyper = more Hypertonic Solutions Cells without cell walls will shrink or die Cells with cell walls will shrivel; the membrane will pull away from the cell wall No cells like this solution and in both cases they may die  So don’t be hyper!

1. Why is the water moving toward the left side of the beaker? 2. Which side of the beaker is hypertonic?

WORD LIST Diffusion Osmosis Selectively permeable Equilibrium Hypertonic Hypotonic Isotonic Know all of these words for the test