NAME: _______________________________DATE: ________BLOCK: _____
OBJECTIVE:
 To look at different ways of transporting things across the plasma membrane of elodea and yeast cells and to tell the difference between the types of transport taking place.
MATERIALS: elodea leaves yeast suspension salt water solution fresh water solution hot plate hot water bath two test tubes two medicine droppers two microscope slides two cover slips digital microscope
Motic Images
Software Congo Red stain
PROCEDURE:
Part 1 Active Transport in Yeast Cells
1. Put approximately 20 drops of yeast suspension into each of 2 test tubes.
2. Add four drops of Congo Red Stain to each tube of yeast and mix by swirling the test tube.
3. Place one of the tubes containing yeast and Congo Red in the hot water bath and boil for 10 minutes .
4. Make one wet mount slide of the boiled yeast and one of the unboiled yeast. MAKE SURE THAT YOU DO NOT MIX UP THESE TWO SLIDES!
5. Observe and compare the boiled and unboiled yeast cells under low and then high power of the microscope. (Yeast cells appear as very tiny circles. Large circles with dark outlines are air bubbles!)

6. REMEMBER, USE ONLY THE FINE ADJUSTMENT KNOB (THE LITTLE
KNOB) TO FOCUS WHEN ON HIGH POWER!
7. Take one picture of each cell treatment (boiled and unboiled) under high power and save each as a .jpg.
NOTE:
This lab concerns the transport of materials across a cell membrane. The lab has nothing to do with the movement of the yeast or elodea cells.
Yeast and elodea cells have no means of movement. They appear to be moving only because the water molecules are moving.
In the boiling water, the water molecules and therefore the yeast cells are moving faster due to the heating. This movement has nothing to do with this lab! FOCUS ON THE COLOR OF THE
YEAST CELLS IN THE TWO TUBES and the shape of the elodea cell membranes!
Part 2 Osmosis in Elodea Cells
1. Prepare a wet mount slide of the elodea leaf.
2. Capture an image of the cells on this slide under the highest power possible and save it as a .jpg image called ElodeaStart.
3. Introduce the salt solution under the cover slip while drawing the solution out the other end of the cover slip with a tissue or paper towel.
4. Wait 5 min. and Capture an image of the cells.
5. Save image as a .jpg image called ElodeaSalt.
6. Introduce the freshwater solution under the cover slip while drawing the solution out the other end of the cover slip with a tissue or paper towel. Be sure to use plenty of water in order to wash out the salt solution.
7. Wait 5 min. and Capture an image of the cells.
8. Save image as a .jpg image called ElodeaFresh.
NOTE:
This lab concerns the transport of materials across a cell membrane. The lab has nothing to do with the movement of the yeast or elodea cells.
Yeast and elodea cells have no means of movement. They appear to be moving only because the water molecules are moving.
In the boiling water, the water molecules and therefore the yeast cells are moving faster due to the heating. This movement has nothing to do with this lab! FOCUS ON THE COLOR OF THE
YEAST CELLS IN THE TWO TUBES and the shape of the elodea cell membranes!

QUESTIONS:
1. What does boiling do to the live yeast cells? (Hint: What would boiling do to most living organisms?)
2. What is different about the color of the boiled yeast compared to the color of the unboiled yeast cells?
3. Are the cell membranes of the yeast permeable to Congo
Red? _______
How do you know this?
4. Using the different types of membrane transport as a guide, what can the unboiled cells do that the boiled cells could not do?
5. Was this lab an example of active transport, passive transport, or both? Think carefully about this question and explain your answer.

6. What type of membrane transport is at work in the elodea cells?
Use your notes as a guide.
7. Describe how the elodea cells change shape as they are exposed to different solutions in this experiment.
8. Why don’t the elodea cells burst when they are exposed to the fresh water?
Writeup: This lab will be graded as by the formal lab report that you will write. This report will contain all five of the pictures that you take for this lab and will follow a format that Mr. Hovan will review with you in class.