Download cell transport in yeast cells

Osmosis and Active Transport in Cells
NAME: _______________________________DATE: ________PERIOD: _____
OBJECTIVE:
 To observe various methods of transport across the membrane of elodea
and yeast cells and to differentiate between the types of transport taking
place.
MATERIALS:
elodea leaves
yeast suspension
salt water solution
fresh water solution
methyl blue stain
Congo Red stain
hot plate
hot water bath
two test tubes
two medicine
droppers
two microscope slides
two cover slips
digital microscope
Motic Images
Software
PROCEDURE:
Part 1
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. Record the color of the yeast cells in Table 1 on the next page.
Part 2
1. Prepare a wet mount slide of the elodea leaf stained with methyl blue.
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 2 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!
TABLE 1
Sample
Observations
Yeast
Boiled
Yeast
QUESTIONS:
1.
What does boiling do to the live yeast cells? (What would boiling do to
most living organisms?)
2.
How do the boiled yeast appear different from the unboiled yeast cells?
3.
Are the cell membranes of the yeast permeable to Congo Red? _______
How do you know?
4.
What are the unboiled cells able to do that the boiled cells could not do?
5.
Was this lab an example of active or passive transport? Think carefully
about this question and explain your answer.
6. What process is at work in the elodea cells?
7. Describe how the elodea cells change shape during the different phases of the
experiment.
8. Why don’t the elodea cells burst when they are exposed to the fresh water?