Diffusion

[2.4 Cell Membranes]

•Students complete formative assessment on diffusion in membranes

• Students complete 2.4 assessment statement answers by hand in table form (similar to DP course outline).

Introduce diffusion & solutions-

• diffusion
• define
• osmosis (H₂0)
• solutions:
• solvent (H₂0)
• solute (Na, Cl, erythrocyte, ribosomes, insulin, albumin, etc.)
• concentrations
• hypertonic (crenate, plasmolysis)
• hypotonic
• hypertonic (lyse, turgor)

Students answer questions:

1. Describe the affect of placing an onion cell in hypertonic NaCl solution.
2. Describe the affect of placing an erythrocyte placed in hyptonic solution.
3. Describe the affect of placing a lettuce cell in isotonic solution.
4. List five (5) dissolved substances found in human blood.
5. Since a cell contains many molecules and proteins dissolved in the cytoplasm, the cytoplasm has high osmotic pressure, meaning it tends to attract water from the blood into the cell.  To prevent the loss of blood volume the body has to balance the osmotic pressure of cell contents.  Suggest how blood prevents loss of the water component (since the body needs to maintain a minimum blood volume.)

• Demonstrate dye diffusion in beaker

Membranes

Plasma membrane S/F:

• phospholipid bilayer
• glycerol
• phosphate
• fatty acids
  
• cholestero
• glycoproteins
• integral proteins
• protein channels (facilitated diffusion; ie. glucose, water)
• protein pumps (use ATP to move ions, ie. Na/K)
  
• immobilized enzymes & electrons transport chains (ACR, photosynthesis)
• hormone binding sites (insulin; insulin action animation)
• cell-cell communication
  
• peripheral proteins
• glycoprotein
• cytoskeleton anchoring
• [cell adhesion?]
  

Describe structure to function relationship in plasma membranes.