Lab: Cell Transport

Essential Question:How do the materials needed for life

get in and out of cells?

Pure H2O H2O + salt Corn syrup

Explain in terms of diffusion what happened to each egg….

80% water

Explain in terms of diffusion what happened to each egg….

Pure H2O(100% water)

H2O + salt(80% water20% salt)

Corn syrup(55% water45% sugar)

Hypotonic HypertonicIsotonic

80% water

80% water

Water diffused into egg,Making it swell (get bigger)

Water diffused out of egg,Making it shrink

Water moved in & out of egg at same rate,So egg stayed same size

What’s the difference between osmosis and diffusion?

• Diffusion = movement of molecules from area of high concentration to low.

• Osmosis = diffusion of water molecules across a membrane.

Red food coloring diffuses through a glass of water

Water moves by osmosis from left to right

1. Based on your observations, which substance passed through the dialysis tubing, the iodine or the starch? How do you know this?

• Iodine.• Starch solution

in bag turned blue-gray.

2. How do you think this substance got through the tubing (assuming the ends were sealed)?

Iodine molecules diffused into bag through tiny holes in membrane.

3. Define diffusion.

• Movement of molecules from area of high concentration to low

4. Sketch the beaker and baggie in the space below. Draw arrows to explain how diffusion occurred in this experiment.

• Iodine molecules diffused into baggie.

5. Based on your observations, which substance passed through the dialysis tubing, the sugar or the Benedict’s solution? How do you know this?

• Sugar.• Water outside

baggie turned orange.

6. Sketch the beaker and baggie in the space below. Draw arrows to explain how diffusion occurred in this part of the experiment.

• Sugar molecules diffused out of the baggie.

starch

Glucose(sugar)

7. How would differences in size of starch and sugar molecules explain the different results observed in parts A and B?

Starch molecules too big to go through holes in membrane.Sugar molecules small enough to go through.

Cell membrane

8. How does this experiment show one important way that life depends on water?

Water is needed to dissolve materials needed for life – oxygen, nutrients, etc. – so they can be transported in & out of cells, and around body.