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Chapter 5


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Chapter 5

  1. 1. Chapter 5 Homeostasis and Transport
  2. 2. Types of Transport <ul><li>Passive transport does not require energy to complete. </li></ul><ul><li>Cells move materials across the membrane without energy. </li></ul><ul><li>This includes: diffusion, osmosis, facilitated diffusion, and diffusion through ion channels. </li></ul>
  3. 3. Diffusion <ul><li>Diffusion is the movement of materials across a membrane using a concentration gradient. </li></ul><ul><li>A concentration gradient is the difference between the number of molecules on each side of the membrane. </li></ul><ul><li>Diffusion happens because the molecules wish to be in equilibrium or be equal on both sides of the membrane. </li></ul><ul><li>Even once equilibrium is achieved, molecules still move back and forth across the membrane randomly. </li></ul>
  4. 6. Osmosis <ul><li>Osmosis is the diffusion of water across the cell membrane. </li></ul><ul><li>Only water is moved in osmosis. </li></ul><ul><li>The direction of osmosis depends on the concentration of molecules outside and inside of the cell. </li></ul>
  5. 7. Hypotonic <ul><li>If the concentration of molecules outside the cell is lower than the concentration inside the cell’s cytoplasm, then the solution is called hypotonic. </li></ul><ul><li>Water will move into the cell to create equilibrium. </li></ul>
  6. 8. Hypertonic <ul><li>When the solution outside the cell has more molecules than inside the cell, the solution is hypertonic. </li></ul><ul><li>Water will move out of the cell to create equilibrium. </li></ul>
  7. 9. Isotonic <ul><li>Both the solution and the inside of the cell are equal. </li></ul><ul><li>Water will move both ways randomly to maintain equilibrium. </li></ul>
  8. 11. How Cells Deal with Osmosis <ul><li>Some animals are only single celled organisms like the paramecium. </li></ul><ul><li>The paramecium is a freshwater pond dweller. </li></ul><ul><li>These paramecia are functioning in a hypotonic environment all the time so water is constantly diffusing into the organism. </li></ul><ul><li>Paramecia have contractile vacuoles that remove excess water from their bodies. </li></ul><ul><li>Sometimes when too much water is added, cells burst and this is called cytolysis. </li></ul>
  9. 13. How Plants Deal with Osmosis <ul><li>Since plants have a cell wall, osmosis affects them differently. </li></ul><ul><li>When osmosis moves water into plant cells, the cell membrane swells but stops against the strong cell wall. </li></ul><ul><li>This is called turgor pressure. </li></ul><ul><li>When plants don’t receive enough water, plasmolysis occurs which makes the plants wilt. </li></ul><ul><li>The cell membrane shrinks away from the cell wall. </li></ul>
  10. 15. Facilitated Diffusion <ul><li>This process is used for molecules that can’t move quickly through the cell membrane. </li></ul><ul><li>Carrier proteins help move the molecules. </li></ul><ul><li>The molecules still move down the concentration gradient so no energy is required. </li></ul><ul><li>Transport of glucose is facilitated diffusion. </li></ul>
  11. 17. Diffusion through Ion Channels <ul><li>Ions such as sodium, potassium and calcium need a channel protein because they cannot pass through the membrane on their own. </li></ul><ul><li>Each type of channel is specific to an ion. </li></ul><ul><li>Some channels are always open and some have gates that open and close depending on the need for the ion. </li></ul>
  12. 19. Active Transport <ul><li>This type of transport goes up or against the concentration gradient. </li></ul><ul><li>Since that is working uphill, energy is required. </li></ul><ul><li>This includes: sodium-potassium pump, endocytosis, and exocytosis </li></ul>
  13. 20. Sodium-Potassium Pump <ul><li>This involves a carrier protein. </li></ul><ul><li>To function normally, animal cells must have a high concentration of sodium outside their cells and a high concentration of potassium inside their cells. </li></ul><ul><li>The sodium-potassium pump works to maintain these differences. </li></ul><ul><li>As sodium comes into the carrier protein and moves outside the cell, potassium comes into the protein and moves inside. </li></ul><ul><li>They switch places. </li></ul>
  14. 22. Endocytosis <ul><li>Some substances such as food particles are too large to move through the cell membrane. </li></ul><ul><li>In endocytosis, the cell encloses external materials in a pouch made from the cell membrane and moves them into the cell. </li></ul><ul><li>The pouch is called a vesicle. </li></ul><ul><li>There are two types of endocytosis: pincocytosis involves transport of fluid and phagocytosis involves transport of solids or whole cells. </li></ul><ul><li>Many animals use phagocytosis to ingest bacteria or viruses that invade the body. </li></ul>
  15. 24. Exocytosis <ul><li>Exocytosis is the reverse. </li></ul><ul><li>In exocytosis, molecules or cells are transported to the outside of the cell from the inside. </li></ul><ul><li>Vesicles are used. </li></ul><ul><li>Cells used exocytosis to release large molecules like proteins into the body from the cell. </li></ul><ul><li>Usually the ER and the golgi are involved in this process. </li></ul>