1. The Eggsperiment A chicken egg is one cell – one unusually large cell! Manipulating it can teach us how our much smaller cells behave and help us understand much about what goes on in our bodies. http://www.enchantedlearning.com/egifs/eggcrosssection.GIF By the way, this cell, like most of yours, has a NUCLEUS which contains the cell’s DNA.

2. How can we enlarge or shrink this cell? This very specialized cell is especially unusual because it has a calcium carbonate (or calcite) shell which obviously restricts its size. How, then, can we dissolve the shell and leave the membrane intact? Just under the shell is a thin, somewhat flexible CELL MEMBRANE; every one of your cells has a similar membrane

3. Dissolving the shell Calcium carbonate will dissolve in acid CaCO 3 + C 2 H 4 O 2 = CO 2 + H 2 O + Ca(C 2 H 3 O 2 ) 2 This leaves the cell membrane in tact And now this cell is much more like the cells in your body – they have membranes, but they don’t have shells!!

4. And after the shell is dissolved… But why does the cell enlarge??

5. One thing we need to know about molecules… They are always moving! They will spread out or diffuse to distribute themselves evenly through any space. Why don’t the fragrance molecules leave the canister? What happened when they are released from the canister? This is the nature of molecules: they diffuse until they achieve an equilibrium. Where else do you see examples of this in real life?

6. Cell membranes are semi-permeable They let only certain materials in and out http://htwins.net/scale2/?bordercolor=whiteDetail ed%2520Map%2520of%2520the%2520Universe Yolk is FAT – BIG molecules !! Acids like vinegar are mostly water - tiny molecules! White is Protein – BIG molecules!

7. So…. Yolk is FAT – BIG molecules !! The big fat molecules and protein molecules can not diffuse out, but they would if they could. Water is able to DIFFUSE into the cell When WATER diffuses it’s also called OSMOSIS And since the cell membrane is semi-permeable… Since acids like vinegar are mostly water and are tiny molecules…. White is Protein – BIG molecules!

8. Osmosis is the diffusion of water across a membrane Yolk is FAT – BIG molecules !! When will the egg stop expanding? When there’s a balance or EQUILIBRIUM of water on the inside and outside of the membrane.

9. So how can we now shrink this “watery” egg? What environment will make water diffuse OUT of the egg? Yolk is FAT – BIG molecules !!