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From Gummy Bears to Celery Stalks: Diffusion and Osmosis


Kevin M. Bonney
Liberal Studies, Faculty of Arts and Sciences
New York University


This is an interrupted case study that intersperses information about diffusion and osmosis with content review and knowledge application questions, as well as a simple experiment that can be conducted without the use of a laboratory. This case study is appropriate for use in undergraduate or high school general biology courses. The case begins with a narrative followed by a set of review questions used to introduce background information about diffusion and osmosis and define the terms active transport and passive transport. The second part of the case includes instructions for a simple experiment using gummy bears soaked in different solution to demonstrate osmosis that can be conducted by students at home or in a classroom. This is followed by an explanation of how the principles of diffusion and osmosis affect animal and plant cells. The case concludes with review questions and discussion of two other simple experiments that further demonstrate osmosis, one of which can be conducted by students at home.

  • Define the following terms: diffusion, active transport, passive transport, osmosis, selectively permeable, hypertonic, hypotonic, and isotonic.
  • Explain and identify what will happen to animal cells and plants cells when placed in a hypertonic, hypotonic, or isotonic solution.
  • Apply knowledge of the above concepts to design and conduct simple experiments that demonstrate osmosis, diffusion, and tonicity.
  • Explain at least two examples of how tonicity and osmosis are relevant to their everyday lives.
Keywords: Diffusion; hypertonic; hypotonic; isotonic; osmosis; passive transport
Topical Area: Scientific method
Educational Level: High school, Undergraduate lower division
Formats: PDF
Type/Method: Demonstration, Discussion, Interrupted, Laboratory
Language: English
Subject Headings: Cell Biology   Biology (General)  
Date Posted: 2/26/2014
Date Modified: N/A
Copyright: Copyright held by the National Center for Case Study Teaching in Science, University at Buffalo, State University of New York. Please see our usage guidelines, which outline our policy concerning permissible reproduction of this work.

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