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:Define osmosis and explain its role within moleculesExplain why osmoregulation and osmotic balance are important body functionsDescribe active transport mechanismsExplain osmolarity and the way in which it is measuredDescribe osmoregulators or osmoconformers and how these tools allow animals to adapt to different environments

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

Students learn about the different structures that comprise cell membranes, fulfilling part of the Research and Revise stages of the legacy cycle. They view online animations of cell membrane dynamics (links provided). Then they observe three teacher demonstrations that illustrate diffusion and osmosis concepts, as well as the effect of movement through a semi-permeable membrane using Lugol's solution.

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 about the techniques engineers have developed for changing ocean water into drinking water, including thermal and membrane desalination. They begin by reviewing the components of the natural water cycle. They see how filters, evaporation and/or condensation can be components of engineering desalination processes. They learn how processes can be viewed as systems, with unique objects, inputs, components and outputs, and sketch their own system diagrams to describe their own desalination plant designs.

Principles of mass transport and electrical signal generation for biological membranes, cells, and tissues. Mass transport through membranes: diffusion, osmosis, chemically mediated, and active transport. Electric properties of cells: ion transport; equilibrium, resting, and action potentials. Kinetic and molecular properties of single voltage-gated ion channels. Laboratory and computer exercises illustrate the concepts. For juniors and seniors. Students engage in extensive written and oral communication exercises.