Observing Active Transport in Yeast Cells
Background:
Yeast is a single-celled eukaryote capable of active transport. Methyl blue is a dye used to help scientists
identify intracellular structures. Methyl blue is small molecule capable of diffusing through a semi-permeable
membrane. In high doses it is toxic to living cells. Today you will observe the response of yeast cells when
placed in an environment with methyl blue.
Materials:
 Microscope
 Microscope slide and coverslip
 Dropper
 0.1% methyl blue solution
Methods:
1. Label two test tubes “boiled” and “not boiled”
2. Add 3mL of yeast and warm sugar water to each test tube
3. Place one test tube into a boiling water bath for 2 minutes
4. Let cool 3 minutes
5. Combine test tubes
6. Place a drop of the yeast onto a microscope slide and add a drop of methylene blue dye
7. Let stand 5 minutes
Hypothesis:
8. Place the slide onto the stage of your microscope and focus.
9. Count and record all the blue and clear cells in your field of view.
Data Table:
Analysis Questions:
1. What is the purpose of heating one test tube?
2. Through which process did the methyl blue enter the yeast cell?
3. What color were the living cells?
4. What color were the dead cells?
5. Why is there a difference in color between the living and dead cells?
6. Some archaea (which are single cell organisms) live in extremely salty water such as the Great Salt Lake or
the Dead Sea. Most types of cells would shrivel and die in this very salty water. How do you think these
archaea prevent water loss while living in very salty water?
7. Name a substance (nutrient/water or waste product) that must be maintained within the human body.
Explain how the body regulates this substance in order to maintain homeostasis. Include a system, organ,
tissue and cell involved. (Use the internet or a book- you may not use sugar as your substance).