Grades: Grades 10 - Biology
Author: Danielle Donaldson
Source: Aliginate portion of lab inspired by: http://imaginationstationtoledo.org/content/2011/09/edible-worms/. Osmosis portion of lab adapted from: http://pslc.ws/macrog/kidsmac/activity/bear.htm.
In the first part of the lab activity, students will be making their own "gummies" similar to gummy worms and Boba fruit spheres using sodium alginate, a polymer found in green algae. The student will then make a connection to osmosis properties by soaking their polymers in distilled water, tap water and salt water, and collected data on mass change.
Students should have an understanding of...
Students should be able to...
This lesson can be used as a reinforcement/inquiry activity during the cell transport unit, as a follow up to information on passive transport (diffusion, osmosis). Students will already have a basic understanding of the cell membrane and passive transport concepts. An opening demonstration can be done for students as an introduction to diffusion where the teacher puts a drop of food coloring in a beaker of water, and asks students to describe what is happening as the food coloring moves from an area of high concentration to an area of low concentration. This can open up discussion about diffusion and passive transport in cells, and why is it important for cells to maintain homeostasis. To get students excited about food chemistry and polymers, bring in various gummy candy such as gummy worms, gummy bears, Boba fruit spheres and other foods in which sodium alginate is used, such as fruit flavored popsicles, yogurt and pie fillings. Ask students to list some of the similarities in these kinds of food (they are gel-like, sticks together, smooth, and thick).
For the exploration portion of this activity, students will be combining their knowledge of osmosis properties to explore the polymer created when sodium alginate and calcium chloride are mixed together. The student worksheet first reviews the concept of osmosis and then goes on to introduce students to the definition of a polymer. In the elaboration portion of the activity, polymers and their uses can be discussed in more detail if time permits. Students, working in groups of 2-4 students, will first begin the activity by making their own sodium alginate gummies following the procedure on the student worksheet. Students will then follow the instructions on the worksheet to complete the osmosis portion of the lab activity, soaking the gummies/Boba overnight and collecting data for their results the next day in lab. In the third portion of the lab, students will simulate reverse osmosis according to the directions in the student worksheet and record their results the following day. Each student will complete their own lab worksheet and turn it into the teacher for assessment.
After laboratory data has been collected and analyzed, the teacher should further explain the concept of osmosis and how the results of the lab should reflect osmosis occurring.
Students can explore the different uses of sodium alginate in various field such as the food industry, cosmetics, textile printing and pharmaceuticals at the following website: http://www.kimica-alginate.com/alginate/application.html.
Students must have a basic understanding of cell structure and function, a preliminary knowledge of passive diffusion, laboratory procedure skills and a basic knowledge of the biological polymers
Students should wear gloves during the activity to eliminate the amount of chemicals on their hands, although all materials are safe. Make sure that students understand that unless food grade chemicals and cooking utensils are used, the product IS NOT edible!
This lesson can be applied to biochemical engineering concepts such as drug delivery and tissue engineering
Unit test on membrane transport, lab report
Grouping Suggestions: Groups student according to supplies available, groups of 2-4 students would work best
Pacing/Suggested Time: If food grade chemicals are used and all measuring materials used are food safe, then "gummies" can be eaten. Add sweetener and flavoring to sodium alginate mixture in order to make them more similar to real gummy worms.