Diffusion, Osmosis and Active Transport Homeostasis Diffusion, Osmosis and Active Transport

Homeostasis The process by which an organism maintains a constant internal environment despite the variations in the external environment Ex. Your body stays at 98.6 degrees Fahrenheit even though the temperature outside changes.

Interest Grabber In or Out? Section 7-3 How is a window screen similar to a cell membrane? Read on to find out. 1. What are some things that can pass through a window screen? 2. What are some things that cannot pass through a window screen? Why is it important to keep these things from moving through the screen? 3. The cell is surrounded by a cell membrane, which regulates what enters and leaves the cell. Why is it important to regulate what moves into and out of a cell?

Cell Membrane Lipid bilayer = gives the cell a flexible structure that forms a strong barrier between the cell and its surroundings. Proteins = form channels and pumps that help move material across the membrane. Carbohydrate chains = chemical identifiers, help cells to indentify other cells.

The Structure of the Cell Membrane Section 7-3 Outside of cell Inside (cytoplasm) Cell membrane Proteins Protein channel Lipid bilayer Carbohydrate chains

Homeostasis, Diffusion, and Osmosis Homeostasis is the maintenance of a stable internal state within an organism. Examples of homeostasis in our bodies are: Regulation of water content Regulation of body temperature Regulation of blood glucose levels Hopefully students will mention water content. Growth, getting nutrients, getting rid of wastes

Concentration The mass of solute in a given volume of solution Which has a higher concentration? 12 grams of salt in 3 liters of water 12 grams of salt in 6 liters of water

Diffusion The spontaneous movement of particles from an area of higher concentration to an area of lower concentration.

Transportation of molecules in plant cells: Osmosis The diffusion of water through a selectively permeable membrane. Right click on web site and click on Open Hyperlink. Play all three

Figure 7-15 Osmosis Section 7-3

Types of Solutions Isotonic = concentrations of water and solute are the same on both sides of the membrane. Hypertonic = more concentrated solution (water moves in) Hypotonic = less concentrated solution (water moves out)

Evaluation: Osmosis Think about what happens to the skin on your hands and toes after soaking in water or going swimming. (Osmosis) Next slide:

Evaluation: answer a or b Osmosis 1. Place your hand in salt water. What happens to the cells of the skin? A. Wrinkled hands B. Smooth hands OR A. Wrinkled hands B. smooth hands

Evaluation: answer a, b, or c Osmosis 2. Cells placed in pure distilled water without any minerals will: A. Remain normal B. CELLS SWELL AND BURST B. C.

Evaluation: answer a or b Osmosis Predict what will happen to the cells of the fish. 3. Place a salt water fish from the Gulf of Mexico into an aquarium of fresh water. A. Fish cells swell and burst B. Fish cells lose water and dehydrate OR A. Dead fish because the cells lysed or burst from too much water.

4. Describe the transportation of molecules in these slides of onion cells.

Facilitated Diffusion Molecules that cannot diffuse across the cell membrane’s lipid bilayer on their own move through protein channels instead.

Facilitated Diffusion Section 7-3 Glucose molecules High Concentration Cell Membrane Protein channel Low Concentration

Active Transport Movement of materials from low concentrations to a higher concentration. Requires energy Carried out by transport proteins (pumps) found in the membrane. Diffusion and osmosis are passive transport. Do not need energy.

Active Transport Section 7-3 Molecule to be carried Energy Molecule being carried Energy

Bulk Transport Endocytosis = process of taking material into the cell by means of infoldings, or pockets, of the cell membrane (forms a vacuole in the cell) Phagocytosis – cytoplasm surrounds and engulfs large particles Pinocytosis – cell takes in liquid from the surrounding environment

Bulk Transport Exocytosis = the membrane of the vacoule fuses with the cell membrane, forcing the contents out of the cell.