Introduction to Cell & Molecular Biology (BIOL121) - Dr. S.G. Saupe (; Biology Department, College of St. Benedict/St. John's University, Collegeville, MN 56321

Study Guide for Diffusion/Osmosis

Goal:  The goal of this unit is to understand how water and solutes move into/out of cells.

Learning Objectives:  Upon completion of this unit the student should be able to:

  1. explain the difference between bulk flow, diffusion and osmosis

  2. compare and contrast isotonic, hypotonic and hypertonic

  3. describe the mechanisms by which cells transport materials across the membrane (consider facilitated diffusion, active transport)

Terms/ConceptsCan you use these in a sentence?  Or, prepare a concept map with them?

  • bulk flow

  • diffusion

  • osmosis

  • dynamic equilibrium

  • solute

  • solvent

  • water potential (Ψ)

  • osmometer

  • hypotonic

  • isotonic

  • hypertonic

  • plasmolysis

  • active transport

  • passive transport

  • facilitated diffusion

  • permease

  • turgor pressure


  1. Compare and contrast hydroxyl and carbonyl function groups

  2. How does the polarity of molecule affects its ability to cross the lipid bilayer?  What types of molecules can cross easily?  which cannot?

  3. What are transport proteins and what do they do?

  4. For each of the following, indicate what kinds of molecules are moved, what parts of the cell membrane involved, how does it work, it is active or passive, which cells do it?:  diffusion, osmosis, facilitated diffusion, exocytosis, endocytosis.

  5. Can you explain the Spuds McSaupe experiment?

  6. Can you answer the questions posted in the Cell Membrane sheet?


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Last updated: July 14, 2009     � Copyright by SG Saupe