1. Part 1- Diffusion and Osmosis

2. I. The Cell Membrane cell membrane into The cell membrane controls what moves into and out of out of the cell lipidbilayer A. Composed of a lipid (fat) bilayer (two part layer) made of molecules called phospholipids hydrophobictails B. The hydrophobic (“water hating”) tails of the away phospholipids move away from the water in the hydrophillic heads cytoplasm, the hydrophillic (“water loving”) heads attracted are attracted to the water of the cytoplasm or external environment of the cell

4. II. Proteins in the membrane Proteinsembedded Proteins are embedded in the lipid bilayer and have several functions: cell markers A. They serve as cell markers to identify the cell transport proteins B. They serve as transport proteins for specific molecules

5. Proteins in the Membrane

6. III. Homeostasis Homeostasisstable changing Homeostasis - maintaining stable conditions inside the cell, even if external conditions are changing maintaindie A. Cells must maintain homeostasis or they will die shivering thermostat B. Examples: sweating/shivering or a room thermostat

7. IV. Diffusion Diffusion - Diffusion - movement of molecules from areas of higherlower higher concentration to areas of lower concentration (from where there are more to concentrations where there are less) until the concentrations are equal naturallyBrownian A. diffusion naturally takes place due to Brownian motion (random movement) of molecules oxygensmall B. water, oxygen, and carbon dioxide are small molecules and diffuse easily across the Membrane oxygen C. Examples: oxygen moving from lungs into red food blood cells, food molecules moving from the waste small intestine into the blood stream, waste molecules of urea moving from the blood into the kidney

8. Diffusion

9. V. Osmosis and Isotonic Situations Osmosiswater A. Osmosis - movement of water molecules across membrane a membrane (such as a cell membrane or artificial membrane) Isotonic same B. Isotonic - (iso- “same”) the concentration of dissolved substances (solute) is the same outside the cell as inside the cell movement Result: there is no net (overall) movement of water molecules (an equilibrium)

12. VI. Hypertonic Situations and Plasmolysis Hypertonic greater outside Hypertonic - (hyper- “above”) the concentration of dissolved substances (solute) is greater outside the cell than inside the cell leave shrink Result: more water molecules leave the cell than enter the cell and the cell will shrink Animal A. Animal cells will shrivel up membranes plasmolysis B. Plant cell membranes will shrink and pull away from the cell wall in plasmolysis

15. VI. Hypotonic Situations and Turgor Pressure Hypotonic outside Hypotonic - (hypo- “below”) the concentration of dissolved substances (solute) is lower outside the cell than inside the cell Result: more water molecules enter the cell than swell leave the cell and the cell will swell burst A. Animals cells will burst if the pressure is too great pushes B. In a plant cell the pressure pushes against the cell wall turgor pressure cell wall and keeps the plant from wilting ( turgor pressure )

17. Part 2- Facilitated Diffusion and Active Transport Larger molecules such as polysaccharides, proteins, and lipids cannot diffuse across the membrane because they are too big.

18. I. Passive Transport Passive transport does not Passive transport - transport which does not require energy energy from the cell because molecules move with with the concentration gradient (from high to low concentrations) Diffusion A.(Simple) Diffusion Facilitated Diffusion B. Facilitated Diffusion - movement of molecules from areas of higher concentration to areas of lower protein channels concentration using protein channels specific 1. Each channel transports a specific type of molecule such as sugar or sodium ions (Na+) signals 2. The channels may open in response to signals from the cell C. Because the cell membrane is controlling what semi - permeable selectively permeable enters and leaves the cell, it is called semi - permeable or selectively permeable

20. II. Active Transport Active Transport does Active Transport - transport which does require energy energy from the cell because molecules move against against the concentration gradient (from low to high concentrations) pump A. Transport proteins pump molecules (such as Na +, K +, and Cl - ) across the membrane ATP B. The energy comes from ATP (more on this later) potassium C. Example - the sodium- potassium pump

22. III. Transporting Large Molecules Endocytosisin environment A. Endocytosis - process of taking in molecules from the environment Phagocytosissolid B. Phagocytosis - “cell eating” taking in solid particles Pinocytosi s liquid C. Pinocytosi s - “cell drinking” taking in drops of liquid Exocytosis rid vacuolevessicle D. Exocytosis - process of getting rid of molecules by merging a vacuole or vessicle with the cell membrane

26. The End!