Osmosis. Question 5: In a lab setting, examine the effects of osmosis on plant cells. Question 6: demonstrate diffusion across a semi permeable membrane.

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Question 5: In a lab setting, examine the effects of osmosis on plant cells.

Question 6: demonstrate diffusion across a semi permeable membrane.

Lab 1: Osmosis and Diffusion

I.        Objectives:

  • Demonstrate diffusion across a semi-permeable membrane
  • Measure the effects of various concentrations of solute in the process of osmosis

  • Differentiate between hypotonic, isotonic, and hypertonic environments

  • Measure and calculate water potential

  • Examine the effects of osmosis on plant cells

II.        Background:

Diffusion: The spontaneous movement of molecules or particles in solution along a concentration gradient (i.e. from areas of high concentration to a low concentration) until there is an equilibrium.

Osmosis: The diffusion of water molecules through a selectively permeable membrane from a region of low solute concentration to a region of high solute concentration.

Equilibrium: A condition in which all influences acting upon it are canceled by others, resulting in a stable, balanced, or unchanging system.

Selectively Permeable Membrane: A membrane that allows only certain materials to pass through it by diffusion.

Hypotonic: A condition in which the inside of the animal or plant cell has a higher solute concentration than its environment.  Osmosis causes a net flow of water into the cell, causing swelling and expansion. This swelling may cause cells without a rigid cell wall to burst.

Hypertonic: A condition in which the environment has a higher solute concentration than inside the animal or plant cell.  Osmosis pressure causes water to flow out of the cells and causing the cell to shrink.

Isotonic:   A solution of equal solute concentration that has no net flow of water across the selectively permeable membrane.

Water Potential: The physical property predicting the direction in which water will flow, governed by solute concentration and applied pressure; the potential energy of


water to move.

Osmotic Potential: The potential for water to move across a selectively permeable membrane, where the osmotic potential of pure water is 0 and any water movement is measured with a negative value.  (Also known as solute potential)

Pressure Potential: The physical pressure on a solution

Osmotic Pressure: The pressure that must be exerted on a solution containing a given concentration of solute separated from a sample of the pure solvent by a membrane.

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III.        Data:

A. Table 1:

Diffusion

B.  Table 2:

Osmosis Investigation



Osmosis


                    C. ...

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