Diffusion and osmosis lab

1. Diffusion and osmosis lab

2. Outline of the day • Turn in your lab reports at the front • More than 10 minutes late = bad • Any questions on last week’s lab? • Quiz • Introduction to the lab • Lab! • Check out • Get a stamp • Make sure I mark you down for attendance

3. Quiz • Ends 10 minutes after it’s started • Ends at: ____

4. Lab this week! • Exploring diffusion and osmosis • Effect of molecular weight on diffusion • Using agar plates! • Effect of temperature on rates of diffusion • Demonstration! • Using osmosis to determine solute concentration • Using dialysis tubing

5. Diffusion • “The movement of molecules or ions from areas of their higher concentration to areas of their lower concentration. Over time, the random movement of molecules will result in the even distribution of the material?” • Krogh, 2005 • The “random movement of molecules or other particles, resulting in even distribution of the particles when no barriers are present” • Purves et al., 1995

6. Diffusion • Start with a gradient of molecules • End with equal concentrations on both sides Image pd by LadyofHats Mariana Ruiz Villarreal - http://en.wikipedia.org/wiki/Image:Simple_difussion_in_cell_membrane.svg

7. An animation of diffusion • http://www.biosci.ohiou.edu/introbioslab/Bios170/diffusion/Diffusion.html

8. Molecular weight • Sum of the mass of all atoms in the molecule • Three molecules • Silver Nitrate (AgNO3) • Mol. Weight: 170 • Iodine potassium iodide (IKI) • Mol. Weight: 293 • Methylene Blue • Mol. Weight: 373 • C16H18N3ClS AgNO3 image PD by Benjah-bmm27 from http://en.wikipedia.org/wiki/Image:Silver-nitrate-2D.svg; mb image PD by Calvero at http://en.wikipedia.org/wiki/Image:Methylene_blue.svg

9. Osmosis • Diffusion of water across a semi-permeable membrane • Water moves down its concentration gradient, just like any other molecule No net movement of water in or out Concentration gradient: 100% water Cell with pure water inside 100% water These solutions are isotonic to each other Pure water (distilled water) Image pd by LadyofHats Mariana Ruiz Villarreal - http://en.wikipedia.org/wiki/Image:Simple_difussion_in_cell_membrane.svg; other art by Marc Perkins

10. Osmosis • Diffusion of water across a semi-permeable membrane • Water moves down its concentration gradient, just like any other molecule Water moves into the cell by osmosis Concentration gradient: 90% water Cell with 10% NaCl solution 100% water The cell is hypertonic to the surrounding solution Pure water (distilled water) Image pd by LadyofHats Mariana Ruiz Villarreal - http://en.wikipedia.org/wiki/Image:Simple_difussion_in_cell_membrane.svg; other art by Marc Perkins

11. Applying osmosis • We’ve got “urine” of an unknown concentration • You need to figure out what concentration it is, using osmosis • Dialysis tubing is a semi-permeable membrane • Water can cross it, but ions and large molecules cannot. • Methods note: • Wet the string before weighing the bag

12. Before you leave • Clean up your work area • Wash glassware and store upside down • Show me your lab report so I can stamp it • Need to have all data fields filled in • Complete at home and then turn in at the beginning of next lab • Remember that we’ll have a quiz at the beginning of the next class • 6-7 questions on today’s lab • 3-4 questions on the lab we’ll do next week

13. Notes for the instructor: • Add any relevant cleanup instructions to the final slide (that slide is a generic one I’m adding to each presentation).

14. License information • This work is licensed under the Creative Commons Attribution-NonCommercial-ShareAlike 3.0 License. To view a copy of this license, visit http://creativecommons.org/licenses/by-nc-sa/3.0/us/ or send a letter to Creative Commons, 171 Second Street, Suite 300, San Francisco, California, 94105, USA. • The slides in this presentation were originally created by Marc C. Perkins (http://faculty.orangecoastcollege.edu/mperkins). • You are free to use, modify, and distribute these slides according to the terms of the Creative Commons license (e.g., you must attribute the slides, no commercial uses are allowed, and future distributions must be licensed under a similar license). • Attribution should be given to Marc C. Perkins (and any later editors), including a link back to Marc’s current website. This applies both while distributing the slides and during use of the slides; attribution during use can be satisfied by, for instance, placing small text on at least one of the slides that has been shown (see below for an example). Slides in this presentation based on those created by Marc C. Perkins. http://faculty.orangecoastcollege.edu/mperkins

15. History • August 2007: Marc Perkins released first version. http://faculty.orangecoastcollege.edu/mperkins (If you modify these slides and redistribute them, add your information to the list)