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Students investigate diffusion, osmosis and study the role of surface area in facilitating diffusion. They apply what they have learned to a blood cell traveling through different concentrations of oxygen. Then, they explore a 3D aquapore embedded in a membrane. Using the Molecular Rover, they fly through the aquapore, and consider how it facilitated their travel from one side of the membrane to another.
Students will be able to:
• Compare diffusion and osmosis.
• Explain how concentration differences affect the overall flow of molecules.
• Contrast molecular movement of materials in and out of equilibrium and describe the dynamic nature of equilibrium.
• Apply the principles of diffusion to red blood cells in a real biological system.
• Explain how increased surface area increases the rate of diffusion.
Possible student pre/misconceptions
• Molecules move with a purpose. They “know” to move from areas of high concentration to areas of low concentration.
• Molecular motion stops when equilibrium is reached
• Diffusion happens at the same speed and is not affected by concentration difference.
• The process of diffusion is dependent on the type of solute.
Additional Related Concepts
Other SAM activities:
The goal of this activity is for students to explore the concepts of passive diffusion, osmosis (and osmotic pressure), and the pumping of materials across a membrane against the natural equilibrium, a process known as active transport.
From Atoms and Energy students learn about conservation of energy and in Electrostatics they learn about ion transfer, which is important when studying chemical and electrical potential in active transport. A background in Atomic Structure is necessary for students to understand that atoms are made of protons, neutrons and electrons. Ions exist as a result of atoms that have gained or lost electrons. Newton’s Laws at the Atomic Scale focuses on the concept that atoms are in constant motion, moving in a straight line until they collide. This underscores the randomness of the motion involved in diffusion.
Phase Change serves as a reference to the states of matter (particularly solids and liquids) that are addressed in this unit. Gas Laws highlights the random motion of gas particles, which behave much like particles dissolved in water or other solvents seen in this unit. Understanding osmotic pressure is also quite similar to the underlying principles behind gas pressure. The Solubility unit is helps students understand why some things can or cannot cross membranes while the Chemical Reactions and Energy activity allows them to explore the chemical energy used to push ions across a membrane.
ATP‐Biological Energy highlights how ATP is used to move materials across the cell membrane. Four Levels of Protein Structure gives students background in how proteins are organized so they can appreciate the details about aquapores provided in this unit. The Structure and Function of Proteins allows students to recognize that one function of proteins is acting as transmembrane molecules.
Directions: After completing the unit, answer the following questions to review.
Created by CC Project: SAM using Molecular Workbench
Last Update: 12/07/2015
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These materials are based upon work supported
by the National Science Foundation under grant numbers
9980620, ESI-0242701 and EIA-0219345
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