Concepts of Biology (BIOL116) - Dr. S.G. Saupe; Biology Department, College of St. Benedict/St. John's University, Collegeville, MN 56321; ssaupe@csbsju.edu; http://www.employees.csbsju.edu/ssaupe/

"Spuds" McSaupe Studies Membranes

 Setting:  The famous scientist Dr. Spuds McSaupe, Ph.D., will visit our class today to discuss osmosis, diffusion and cell membranes. He will show us an experiment involving potato tubers. Spuds will obtain a beaker of water and a beaker of concentrated salt solution. He will then cut cores from a potato, measure the length of each, and then incubate them in either water or a salt solution, respectively. This "experiment" is diagrammed as follows:

Make some predictions:

1. The length of the core in water will:   increase, decrease, or remain the same
2. The water pressure in the cells of the core incubated in water will: increase, decrease, or not change.
3. The turgidity of the core in salt will:  increase, decrease, not change
4. The concentration of water in the cells of the potato core incubated in the salt solution will:   increase, decrease or not change
5. The concentration of salt in the beaker will:   increase, decrease, not change
6. In which core will the cells of the potato be most likely to plasmolyze?   water, salt

 Results:

• How accurate were your predictions?
  
  
• Describe the experiment using the following terms: hypertonic, isotonic, hypotonic, osmotic pressure, osmosis, turdigity, plasmolysis, and  osmotic concentration.