1. Diffusion and Osmosis
Kidney Dialysis Simulation Lab
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2. After completing this activity,
students will be able to:
 Define the terms diffusion, osmosis,
hypotonic, hypertonic, isotonic
 Construct a model to simulate the action
of a kidney
 Relate changes in color, turgor, and salt
concentration to evidence of osmosis
 Evaluate the function of the kidney as an
evolutionary adaptation to life on land.
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3. Think about the diffusion of…
 Molecules
Perfume
Smells and Gases
Sugar in iced tea
A drop of food coloring in
water
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4. Diffusion: High concentration
to low concentration
#NSB2014 Diffusion is passive – doesn’t require any energy 4

5. Perfume molecules expand to
fill all the space (because
they are in motion)
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6. Semi permeable membrane
– allows certain molecules to
diffuse through it
Small molecules fit through the
membrane, larger ones do not
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7. Osmosis
 The spontaneous net movement of solvent
molecules through a semi-permeable
membrane into a region of
higher solute concentration, in the
direction that tends to equalize the
solute concentrations on the two sides
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8. Turgor Pressure – internal
cellular pressure
A B C D
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9. Water (osmosis) balance in cells
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The outside of a red blood cell is a semi permeable membrane

10. What affects the rate of diffusion?
 Temperature
 higher temperature = faster diffusion
 Adding energy
 (when you stir sugar into your coffee, does it dissolve
faster or more slowly?)
What affects rate of diffusion across a semi-permeable
membrane?
 Difference in concentration of a substance inside vs.
outside the membrane –> bigger difference = faster
diffusion
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11. Vocabulary to know
 Isotonic – water enters and leaves at
same rate (equilibrium, balance,
homeostasis)
 Hypertonic – salt water (what would
happen to your body if you ate too much
salt?)
 Hypotonic – distilled water (what would
happen to your body if you drank too
much water?)
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12. Vocabulary to know
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13. Could we put a salt water fish
like a clownfish in a freshwater
fish tank with a goldfish?
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14. Today’s Lab: Simulated
Kidney
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15. Why are we going to talk
about Kidneys?
• Metabolism, Homeostasis
• All the blood in the body must pass
through the kidneys.
• Kidneys filter all waste out of your
body (urea, ammonia, salts, drugs,
water, and other toxic substances)
• If you have no kidney function, you
have to get dialysis, or you will be
poisoned with waste.
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16. Kidney Dialysis
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17. What is Dialysis Tubing?
 Dialysis Tubing is a type of semi-permeable membrane
tubing made from regenerated cellulose (plant
material) or cellophane. It is used for diffusion. It
allows the passage of small molecules but not larger
ones.
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18. Biological Processes
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19. Things that affect diffusion
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