1. Diffusion and Osmosis Bio 21L Spring 2003

2. Molecular Motion Molecules posses kinetic energy. Random motion Rotational, translation & vibration movements Brownian Movement: random, zigzag movement, arising due to collisions of molecules with particles. BM is typical of colloids.

3. Diffusion Net movement of molecules from an area of high concentration to one of lower concentration Fick’s First law of Diffusion: Rate of diffusion is directly proportional to concentration

4. Osmosis Diffusion of molecules across a semi-permeable membrane from a place of higher concentration to one of lower concentration until the concentration on both sides is equal Osmolarity: Concentration of osmotically active particles Tonicity: The osmotic pressure/tension of a solution wrt blood Hypertonic solutions: are @higher osmotic pressure than the reference solution

5. Hypertonic solutions: are @ higher osmotic pressure than the reference solution. Exosmosis Hypotonic: are @ lower pressure than reference. Endosmosis Isotonic: are @ the same osmotic pressure as reference; e.g. 0.9% NaCl Sol; 5% sucrose sol with human blood cells

6. Dialysis Separation of molecules based on size, using a semi-permeable membrane. Semi-permeable membranes: natural-cell membranes; synthetic- nitrocellulose memb. Factors affecting rate: Pore size of memb; Size of molecule; polarity of molecules; tonicity of solution outside dialysis bag

7. Water Potential ۴ & Uptake of Water by Plants Forces of adhesion & cohesion Evaporation & transpiration at leaf tip Generation of water potential Endosmosis into root cells Water uptake

8. Haemeolysis & Crenation: Ghost Studies Loss of water by cells- cell shrinkage or crenation In RBCs-leaves just membranes-used extensively to study memb structure In plant cells- cell shrinkage- allows plant cell memb to be seen Plasmolysis-rupturing plant cells by dunking in hypotonic solution. Turgid cell- plant cells that maintain a good osmolarity & tonicity- appear round & happy!

9. Cool! Let’s get started!