Chem Intro / Name:
Ms. Manning’s Potatoes need an Upgrade
Your job title: Lab Technician
Scenario: You are a lab technician working for Monsanto, a large agricultural company that uses genetic engineering to grow different types of crops. Ms. Manning, a potato farmer in P.E.I. has contacted your company and explained that she thinks the starch content of her potatoes is too low. She would like to grow a potato that contains more starch because the paper company that is using her starch to make photocopy paper is paying her for the amount of starch that she provides, not by the number of potatoes. The genetic engineering division of Monsanto has developed a new potato for Ms. Manning which she has recently used to grow her crop this season. Your boss at Monsanto would now like you to determine whether or not the starch content has increased in the new crop of potatoes. In a previous test on the old potato variety, another lab technician determined that the solute concentration within the potato was 10%. You must test the new variety of genetically engineered potato and determine if the solute concentration is higher or lower than 10%.
Background information: The cells of potatoes, like all plant cells, are surrounded by a selectively permeable membrane which is able to control the amount of water and solutes within the cell. Inside the cells of the potato are molecules of starch (complex sugar). The large size of the starch molecules prevents them from moving across the membrane. During this lab you will use your understanding of osmosis and diffusion to determine what the solute concentration of the inside of a potato cell is by investigating the effect that various sugar concentrations has on each potato slice. The definitions of the terms hypotonic, hypertonic, and isotonic will help you.
This is an Inquiry Lab, therefore you will not be given a procedure to follow. It is up to you to determine how you will determine the solute concentration of Ms. Manning’s potatoes.
Remember: your results on day two will not tell you anything if you do not take measurements on day one. What should you be measuring on day one if you are hoping to find the difference that the solutions have on the potato slices?
DAY ONE
The following solutions have been prepared for you.
- 0% (distilled water)
- 5% table sugar solution
- 10% table sugar solution
- 15% table sugar solution
- 20% table sugar solution
- 25% table sugar solution
- 30% table sugar solution
- 35% table sugar solution
- 40% table sugar solution
- 45% table sugar solution
- you must cut sections of potato that are equal in size and shape and small enough to be completely submerged in a test tube.
- cover your test tubes with rubber stoppers when you are finished
DAY TWO
Measure your potato slices and consider the following questions when you are preparing your Results and Discussion sections.
- Record the changes in your potato slices in a chart. I recommend that you use the % change that occurs.
- Create a bar graph of your results.
- Which sugar concentration(s) caused the greatest change to the potato slices? Explain why you think that this happened.
- Which sugar concentration(s) caused the smallest change to the potato slices? Explain why you think that this happened.
- What is the best estimate of the solute concentration inside the potato slices?
Do you recommend that Monsanto develop another genetically engineered potato for Ms. Manning or does the new variety show an increased starch content?
Your Lab Report Must Include:
1. Title
2. Brief Introduction
3. Purpose
4. Materials
5. Hypothesis
6. Procedure (in past tense)
7. Observations/Results
8. Discussion
9. Conclusion