1. Diffusion, osmosis; cell membranes
Lab 4

2. Solution
Making a saline water solution by dissolving salt (NaCl) in water. The salt is the solute and the water the solvent.

3. Concentration
These glasses containing red dye demonstrate qualitative changes in concentration. The solutions on the left are more dilute, compared to the more concentrated solutions on the right.

4. Diffusion-Brownian movement
The rate of diffusion is dependent on such factors as the temperature, the size of the molecule, concentration gradient and the type of medium.

6. Diffusion and differentially permeable membranes
A differentially permeable membrane prevents the movements of some molecules but not others.

7. Osmosis Special case of diffusion
Osmosis is the diffusion of water across a differentially permeable membrane.
Water molecules follows its concentration gradient and moves from the area of higher concentration to the area of lower concentration.

8. Osmosis and the rate of diffusion along a concentration gradient
Isotonic- two solutions have equal concentrations of solutes.
Hypotonic- a solution with a lower concentration of solutes, especially those solutes that do not pass across the surrounding membranes.
Hypertonic- a solution with a high concentration of solutes.

9. Osmotic effects on cells
In an hypertonic solution
Animal
cells
Plant
plasma
membrane
chloroplast
nucleus
cell
wall
Vacuoles fill with water
turgor pressure develops
chloroplasts - next to the cell wall
Vacuoles lose wate
the cytoplasm shrinks(plasmolysis)
chloroplasts- in the center of the cell
Water mainly enters the cell, which may
burst (lysis)
No net movement of water
Water mainly leaves the cell, which
shrivels (crenation)
central
vacuole
In an isotonic solution
In an hypotonic solution
No net movement of water
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12. Cellular membranes

13. Thickness: 6-10 nm
Functions:
1. retarding diffusion of selected molecules
2. housing receptor molecules that detect other cells or organelles
3. providing sites for active and passive transport of selected molecules
4. organizing life processes by providing surfaces to accommodate chemical reactions
5. helping maintain the integrity of cells

16. Procedure 9.2
Procedure 9.3
Procedure 9.4 (Start this one first)
Procedure 9.5
Procedure 9.6 (Observe only)
Procedure 9.7 (Observe only)
Procedure 9.8
Procedure 10.1