Lab 3 diffusion and osmosis fall 2014

Diffusion and OsmosisKidney Dialysis Simulation Lab

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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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Think about the diffusion of…

MoleculesPerfumeSmells and GasesSugar in iced teaA drop of food coloring in

water

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Diffusion: High concentration to low concentration

#NSB2014 4Diffusion is passive – doesn’t require any energy

Perfume molecules expand to fill all the space (because they are in motion)

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Semi permeable membrane – allows certain molecules to diffuse through it

#NSB2014 6Small molecules fit through the membrane, larger ones do not

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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Turgor Pressure – internal cellular pressure

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A B C D

Water (osmosis) balance in cells

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The outside of a red blood cell is a semi permeable membrane#NSB2014

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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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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Vocabulary to know

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Could we put a salt water fish like a clownfish in a freshwater fish tank with a goldfish?

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Today’s Lab: Simulated Kidney

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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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Kidney Dialysis

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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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Biological Processes

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Things that affect diffusion

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