Monday, October 6, 2008

Lab 1

Today we received our packets for Lab 1. The lab includes several experiments having to do with osmosis and diffusion.

This lab focuses on:

  • Investigation the processes of diffusion and osmosis in a model membrane system
  • Investigating the effect of a solute concentration on water potential as it relates to living plant tissues

For this lab you must understand:

  • Mechanisms of diffusion and osmosis and their role in cells
  • The effects of solute size and concentration gradients on diffusion across selectively permeable membranes
  • The effects of a selectively permeable membrane on osmosis and diffusion between two solutions separated by the membrane
  • The concept of water potential
  • The relationship between solute concentration and pressure and the water potential of a solution
  • The concept of molarity and its relationship to osmotic concentration

Properties of water potential will be useful in this lab

  1. Water moves across a selectively permeable membrane from an area of higher water potential to an area of lower water potential
  2. Water potential can be positive or negative.
  3. Solute potentials result from the presence of solutes and are always negative. The higher the concentration of solutes the smaller, or more negative, the pressure is.
  4. Pressure potential is zero unless some force is applied, like that applied by a cell wall
  5. Pure water at atmospheric pressure has a water potential of zero

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