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Warm up

Explore how indicators and membrane permeability affect diffusion in this lab activity. Learn about the concepts of diffusion and osmosis through various experiments.

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Warm up

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  1. Warm up How did we use indicators in the Diffusion Lab? Find your Diffusion Lab

  2. Diffusion Through a Membrane DIN – Turn your lab over to the back. Write down a few sentences about what is happening in the video AND why it is happening. EGG VIDEO

  3. Review of the Cell Membrane • The Cell Membrane is Semi-Permeable or Selectively Permeable • Small molecules (like glucose) are able to pass through the membrane while large molecules (like starch) cannot pass through

  4. Diffusion Through A Membrane glucose molecule PART of a starch molecule

  5. What we used for the lab • Dialysis Tubing – used to make a “cell” that will allow small particles to pass through and not large particles • Glucose Solution – a simple sugar made of one small molecule of sugar • Starch Solution – a complex carbohydrate made of hundreds of simple sugars bonded together

  6. Indicators • Starch Indicator Solution – (Iodine), a really small molecule (It’s only 2 atoms big) • Glucose Indicator Solution – Benedict’s solution

  7. Initial Cell “Cell” with glucose and starch Water and starch indicator solution

  8. The Final Cell The water stayed amber The cell turned blue-black Water from outside the cell tested positive for glucose

  9. Quick Video of Iodine (Starch Indicator Solution) diffusing INTO the Cell!

  10. What Happened?? • Glucose was small enough to pass through the membrane so it ended up in the water outside the cell • Starch was too big to pass through the membrane so it didn’t get out of the cell • Iodine (starch indicator solution) was small enough to pass through the membrane so it ended up in the cell turning the cell blue-black

  11. Diffusion Through a Membrane

  12. Diffusion Through a Membrane

  13. RED ONION IN FRESH WATER

  14. Red Onion in Fresh Water cytoplasm red onion cells in tap water cell membrane cell wall

  15. Add Salt Water to Cells bathing the cells in NaCl = salt water, by “wicking” it through NaCl

  16. RED ONION IN SALT WATER

  17. Diffusion Through a Membrane cytoplasm red onion cells in salt water cell membrane cell wall

  18. Diffusion Through A Membrane bathing the cells in distilled water, by “wicking” it through

  19. Diffusion Through a Membrane cytoplasm red onion cells in distilled water – returned to normal cell membrane cell wall

  20. Diffusion Through A Membrane Which cell is in distilled water and which is in salt water?

  21. Diffusion Through A Membrane Applications – • salt on roads to melt snow • intravenous saline solutions • salty foods make you thirsty • salt on slugs to kill them • salty foods do not spoil as easily • gargling with salt water • digestion of starch to glucose

  22. Quick video of what happened to iodine in “cell” tube A diffusion lab for absent students Student summary of diffusion state lab Osmosis demo with raw egg

  23. Activity – Analysis Questions • Your table will be assigned one question from the analysis section on pages 8 and 9 • Work on the question with your table for 5 minutes and put your answer on your easel. • Be ready to share and explain to your classmates ** If you finish early, check that ALL other sections of the lab are complete

  24. REGENTS PRACTICE Reflection Answer on looseleaf and attach to lab • How did we observe diffusion and osmosis in this lab activity? Did this help with your understanding of these concepts? Explain. • Why was lab safety important during this activity? • What was your favorite part of this lab? What was most challenging?

  25. Ticket out the Door Think of our experiment yesterday… • What molecule diffusedOUT of the “cell”? Why was it able to? • What molecule could NOTdiffuse out of the “cell”? Why not? • What molecule diffused INTO the cell? What did it react with in the cell? How could you tell it reacted?

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