Students compare and contrast passive and active transport by playing a game to model this phenomenon. Movement through cell membranes is also modeled, as well as the structure and movement typical of the fluid mosaic model of the cell membrane. Concentration gradient, sizes, shapes and polarity of molecules determine the method of movement through cell membranes. This activity is associated with the Test your Mettle phase of the legacy cycle.

Biology is designed for multi-semester biology courses for science majors. It is grounded on an evolutionary basis and includes exciting features that highlight careers in the biological sciences and everyday applications of the concepts at hand. To meet the needs of today’s instructors and students, some content has been strategically condensed while maintaining the overall scope and coverage of traditional texts for this course. Instructors can customize the book, adapting it to the approach that works best in their classroom. Biology also includes an innovative art program that incorporates critical thinking and clicker questions to help students understand—and apply—key concepts.

By the end of this section, you will be able to:Explain why and how passive transport occursUnderstand the processes of osmosis and diffusionDefine tonicity and describe its relevance to passive transport

Worksheet that goes over the types of transport associated with a cell membrane.

Movement of ions in and out of cells is crucial to maintaining homeostasis within the body and ensuring that biological functions run properly. The natural movement of molecules due to collisions is called diffusion. Several factors affect diffusion rate: concentration, surface area, and molecular pumps. This activity demonstrates diffusion, osmosis, and active transport through 12 interactive models.

Using ordinary household materials, student “biomedical engineering” teams design prototype models that demonstrate semipermeability under the hypothetical scenario that they are creating a teaching tool for medical students. Working within material constraints, each model consists of two layers of a medium separated by material acting as the membrane. The competing groups must each demonstrate how water (or another substance) passes through the first layer of the medium, through the membrane, and into the second layer of the medium. After a few test/evaluate/redesign cycles, teams present their best prototypes to the rest of the class. Then student teams collaborate as a class to create one optimal design that reflects what they learned from the group design successes and failures. A pre/post-quiz, worksheet and rubric are provided.

Through two lessons and five activities, students explore the structure and function of cell membranes. Specific transport functions, including active and passive transport, are presented. In the legacy cycle tradition, students are motivated with a Grand Challenge question. As they study the ingress and egress of particles through membranes, students learn about quantum dots and biotechnology through the concept of intracellular engineering.

Students learn that engineers develop different polymers to serve various functions and are introduced to selectively permeable membranes. In a warm-up activity, they construct models of selectively permeable membranes using common household materials, and are reminded about simple diffusion and passive transport. In the main activity, student pairs test and compare the selective permeability of everyday polymer materials engineered for food storage (including plastic grocery bags, zipper sandwich bags, and plastic wrap) with various in-solution molecules (iodine, corn starch, food coloring, marker dye), assess how the polymer’s permeability relates to its function/purpose, and compare that to the permeability of dialysis tubing (which simulates a cell membrane).