Name:______Block:______Date:______

Virtual Osmosis and Diffusion Lab Activities

Lab Activity #1: Movement Across a Membrane

Log on to:

Directions: Read through the website and conduct the activity by following the instructions. (Typically you press the red dot to advance the activity.) Answer the questions on this paper as you move through the activity.

What did you place INSIDE the dialysis bag? ______

What did you place in the beaker OUTSIDE of the dialysis bag? ______

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The following table describes the indicators that are used to test for different substances.

Test

/ Positive Result /

Negative Result

IKI (iodine) test for starch / dark blue/purple/black solution / no color change or amber solution
Barium chloride (BaCl2) test for sulfate(SO4) ions / milky or cloudy white precipitate formed / no color change or no precipitate
Silver nitrate (AgNO3) test for chloride (Cl-)ions / milky or cloudy white precipitate formed / no color change or no precipitate
Biuret test for protein / light purple solution / no color change or light blue solution

Enter “+” or “-“ for each test :

Results of Tests for Substances in Beaker

Initially / After incubation

Starch

Sulfate ion
Chloride ion
Protein

Results of Tests for Substances in Bag

Initially / After incubation

Starch

Sulfate ion
Chloride ion
Protein

Follow-up Questions:

1) To which substances was the dialysis tubing permeable?

  1. Starch/sulfate ion
  2. Starch/protein
  3. Chloride ion/sulfate ion
  4. Protein/chloride ion

2) To which substances was the dialysis tubing impermeable?

  1. Starch/sulfate ion
  2. Starch/protein
  3. Chloride ion/sulfate ion

D. Protein/chloride ion

3) Suggest a reason for the failure of some substances to diffuse through the membrane. Hint: The chemical formula for sulfate is S04 and for starch (C6H10O5)700. ______

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4) Can different materials diffuse through a membrane in opposite directions at the same time? Support your statement with evidence from your experiment. ______

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5) In what way is the dialysis membrane like the cell membrane? ______

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6) In each case, the molecules moved from ______concentration to ______concentration.

7) Dialysis is a technique used to purify blood in cases of kidney failure. During dialysis, what substances would you want to remove from the bloodstream? What substances would you want to remain in the bloodstream? Hint: You may have to look up how dialysis works online.

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Lab Activity #2: Osmosis in Cells

  • Log on to
  • Click on:
  • The Biology Place (on the right side of the screen)
  • Biocoach
  • Biomembrane I: Membrane Structure and Function
  • Concept 2: Osmosis: Movement of Water Across Membranes (on the left side of the screen)

Osmosis (movement of water across membranes) depends on the relative concentration of solute molecules on either side of the membrane. The presence or absence of cell walls influences how cells respond to osmotic fluctuations in their environment.

Click on Review

Looking at the diagram above. Describe the difference between the three types of solutions.

The small circles represents dissolved solutes like salt, glucose, and amino acids. You can assume that the additional space surrounding the solutes is water.

hypotonic - ______

______

isotonic - ______

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hypertonic - ______

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Click on Next  Cells in Isotonic Solution

  1. What is the concentration of salt in animal cells? ______
  2. When cells are in isotonic solution, is there movement of water into or out of the cell? If so, describe this movement. ______

______

Click on Next  Cells in Hypotonic Solutions

Describe the net movement of water molecules when cells are placed in a hypotonic solution. ______

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Click on A Closer Look  A Closer Look at Plant and Animal Cells in Hypotonic Environments

**Make sure to ANIMATE the graphics.**

1. What happens to plant cells when placed in a hypotonic solution?

______

______

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2. What happens to an animal cell when placed in a hypotonic solution? (3 pts)

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3. Account for the different reactions between plant and animal cells when placed in a hypotonic environment. ______

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4. What cell structure prevents lysis in many single-celled protists living in a fresh water environment? ______

Click  Back to Review then Next  Cells in Hypertonic Solutions

Describe the net movement of water molecules when cells are placed in a hypertonic solution. ______

______

Click on A Closer Look  A Closer Look at Plant and Animal Cells in Hypertonic Environments

**Make sure to ANIMATE the graphics.**

Compare and contrast what happens to plant and animal cells when placed in a hypertonic solution. ______

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