1. Diffusion And Osmosis

2. Homeostasis Homeostasis: A stable internal environment. *In a cell, factors such as pH and the concentrations of other substances must ALWAYS remain the same (even when the external environment changes). It is the special properties of the cell membrane that help the cell maintain homeostasis.

3. Quick physics lesson… Atoms and molecules are always in motion. This energy of motion is called kinetic energy. The atoms of gases move about the most freely, but even the molecules of solids move about a fixed point.

4. Diffusion Diffusion: Movement from an area of greater concentration to an area of lesser concentration. *Diffusion occurs because molecules are in constant motion… Diffusion Animation

5. Question: Faster Turns out, temperature is nothing more than a measure of how fast molecules are moving. Do molecules diffuse faster or slower in warm temperatures?

6. Diffusion across membranes is determined largely by the size and the chemical charge of the molecule. Oxygen, glucose, carbon dioxide, and water can diffuse across a cell membrane.

7. * Osmosis * the diffusion of water across a semi-permeable membrane from a region of high water concentration to and area of low water concentration.

8. What does mean? What does “Water Concentration” mean? -water concentration refers to the number of water molecules in a given volume. **Which has greater water concentration, distilled water or salt water?** Osmosis Animation

9. Osmotic Pressure: the increase in pressure resulting from the flow of water in osmosis.

10. Isotonic Isotonic Solution: the environment has the Same concentration of dissolved substances as inside the cell. 80% water 20% dissolved substances 80% water 20% dissolved substances Hypotonic Hypotonic Solution: the environment has a Lower concentration of dissolved substances than inside the cell. Distilled water (100% water) Hypertonic Hypertonic Solution: the environment has a Higher concentration of dissolved substances than inside the cell. 70% water 30% dissolved substances

11. Summed up:

12. “Bulk” Passage into and out of the Cell When the plasma membrane is extended to engulf large particles The reverse process. Proteins or other molecules are secreted out of the cell this way. Phagocytosis: solids/foodsPinocytosis: liquids Endo and exocytosis animation

14. What’s the difference between passive and active transport? PASSIVE TRANSPORT: PASSIVE TRANSPORT: when materials move across cell membranes without using cell energy. *diffusion, facilitated diffucion, and osmosis are examples *water, oxygen, carbon dioxide, glucose ACTIVE TRANSPORT: ACTIVE TRANSPORT: the movement of materials across the cell membrane that requires the use of cell energy (ATP) http://fig.cox.miami.edu/~cmall ery/150/memb/c8x16types- transport.jpg

15. Cells use active transport to: Transport molecules that are too BIG to diffuse~ AND Transport molecules from LOW concentration to HIGH concentration (opposite of diffusion) http://fajerpc.magnet.fsu.edu/Education/2010/Lectures/12_Membrane_Transport_files/image032.jpg

16. Active transport animation