Cell Membrane Permeability
9/15/2017
What does it mean for something to be semipermeable? This week in science, 7th and 8th graders created a model replicating a cell that would demonstrate the answer to this question. They put a starch solution a Ziplock bag and placed it in an iodine solution to see if the plastic was permeable in any way. What they discovered was that it was semipermeable. Only some substances could move through the membrane of the baggie. To their surprise, the starch solution inside the baggie turned purple and the remaining solution outside the “cell” became a lighter yellow/brown than the original iodine solution. So, while the iodine molecule could diffuse through the membrane, the starch compound was too big to pass through. Similar results were found in their original Eggsperiments. Here they used a variety of solutions and measured the size of the egg to verify the direction of osmosis (passive transport). Learning the meaning of the words and concepts they use in science is only one objective of the lab. Students must also think and write in an organized, scientific fashion so that anyone could duplicate their work and get similar results. Students hypothesize about the results they expect. This requires activating all prior knowledge on the subject and applying new concepts that they are learning. Next week, students will test their knowledge and then move on to cell processes which build on what they have been learning about so far. Comments are closed.
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Sarah Mariner
Ms. Mariner earned her Bachelor of Science degree in Biological Science from Colorado State University, and was awarded a teaching certificate through the University of Alaska, Southeast. Her varied background includes being an environmental education field instructor in Massachusetts, Colorado, and Baja, Mexico. She also served two years as a Peace Corps volunteer in the Dominican Republic. Archives
April 2021
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