Biological Membranes

1
Biological Membranes

• Solvent solute(s) solvent
• examine diffusion of solutes
• examine diffusion of the solvent (water)
• osmosis

2
Diffusion exercise

• Movement of molecules from high concentration to
  low concentration (down the concentration
  gradient)
• diffusion through
• solid (agar plates)
• liquid
• gas

3
Diffusion cont.

• Rate
• temperature (increase diffusion w/ increase
  temp)
• MW (increase diffusion w/ decrease MW)
• solute MW T in oC
• potassium permanganate 294.21 5o, 25o
• Janus Green 511.09 5o,25o

4
Osmosis exercise, demo movement of water across a
differentially permeable membrane

• Setup 1
• water molasses

• Setup 2
• water molasses

5

• water 10 sucrose, water 20 sucrose, water
• 40 sucrose, water water, 40 sucrose

6
Permeability of Membranes, exercise

• 10 ml of starch protein NaCl Na2SO4
• test water for
• Starch w/ iodine
  (blue-black ppt.)
• Cl - w/ AgNO3( milky white ppt.) SO4-
  w/ BaCl2 ( white ppt.)
• Protein w/ biuret

7
Tonicity exerciseplant cells

• Turgid
• hypotonic solution
• water enters cell
• chloroplasts are at the periphery of the cell

• Plasmolyzed
• hypertonic solution
• water leaves the cell
• chloroplasts are at the center of the cell

8
Tonicity exercise animal cells

• normal (0.85 NaCl)
• isotonic
• no net movement of water
• crenated (10 NaCl)
• hypertonic 0.85 NaCl
• water leaves in the cell
• hemolyzed (0.45 NaCl)
• hypotonic
• water enters