1. CELL (PLASMA) MEMBRANE FLUID-MOSAIC MODEL FIRST DETERMINED BY S.J. SINGER

2. The current best model of what a cell membrane looks like is in the figure below. As you can see it is made up of two parts. They are the phospholipids (magenta and green), the proteins (orange and red), and the carbohydrates (black). The current best model of what a cell membrane looks like is in the figure below. As you can see it is made up of two parts. They are the phospholipids (magenta and green), the proteins (orange and red), and the carbohydrates (black).

3. \\FHS-dc1\SHARE\Biology\CIRCLE\Cells\Videos\bilayer.mov \\FHS-dc1\SHARE\Biology\CIRCLE\Cells\Videos\bilayer.mov Phospholipid bilayer \\FHS-dc1\SHARE\Biology\CIRCLE\Cells\Videos\bilayer.mov The heads of the PHOSPHOLIPIDS are composed of glycerol and a phosphate group and like to dissolve in water. The tails of the PHOSPHOLIPIDS are mostly fatty acids made up of long carbon and hydrogen chains. Carbon and hydrogen chains are not polar and do not like to dissolve in water.

5. Passive Transport DIFFUSION Diffusion is the movement from a high concentration of molecules to a low concentration of molecules. Molecules can diffuse across membranes through the phospholipid bilayer or using a special protein (facilitated diffusion). Either kind of diffusion does NOT need energy from the cell.

6. Some special proteins move certain molecules across cell membranes only with the help of cell energy (either directly or indirectly).

7. DIFFUSION

8. OSMOSIS  When water diffuses, the process is called osmosis. Water moves from a high concentration of water (less salt or sugar dissolved in it) to a low concentration of water (more salt or sugar dissolved in it). LYSIS OF A RED BLOOD CELL TURGID ELODEA CELLS

9. If the concentration of solute (salt) is equal on both sides, the water will move back and forth but it won't have any result on the overall amount of water on either side. "ISO" means the same EFFECTS OF OSMOSIS ON ANIMAL & PLANT CELLS

10.  The word "HYPO" means less, in this case there are less solute (salt) molecules outside the cell, since salt sucks, water will move into the cell.  The cell will gain water and grow larger. In plant cells, the central vacuoles will fill and the plant becomes stiff and rigid, the cell wall keeps the plant from bursting  In animal cells, the cell may be in danger of bursting, organelles called CONTRACTILE VACUOLES will pump water out of the cell to prevent this.

11. The word "HYPER" means more, in this case there are more solute (salt) molecules outside the cell, which causes the water to be sucked in that direction. In plant cells, the central vacuole loses water and the cells shrink, causing wilting. In animal cells, the cells also shrink. In both cases, the cell may die. This is why it is dangerous to drink sea water - its a myth that drinking sea water will cause you to go insane, but people marooned at sea will speed up dehydration (and death) by drinking sea water.

12. Water will move in the direction where there is a high concentration of solute (like salt) and hence a lower concentration of water.

14. ACTIVE TRANSPORT  Active Transport - this type of transport requires that the cell use energy, because substances are moving against the concentration gradient.  Endocytosis - cell takes in small & large particles. Ex. Pinocytosis & Phagocytosis  Exocytosis - cell gets rid of particles, opposite of endocytosis --------------------------------------------------------------  CYCLOSIS- Circulation or streaming of the cytoplasm. Ex. Chloroplasts

15. Cyclosis of chloroplasts

16. Moving molecules with cell energy is called active transport. The cell energy is the ATP made in the mitochondria.