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Cell Transport

Cell Transport. Modern Biology Chapter 5. Passive transport. Transport across a membrane without the expense of energy Video. Equilibrium. Equal concentration of molecules of a substance throughout a space All things move toward equilibrium unless energy is added. Diffusion.

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Cell Transport

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  1. Cell Transport Modern Biology Chapter 5

  2. Passive transport • Transport across a membrane without the expense of energy • Video

  3. Equilibrium • Equal concentration of molecules of a substance throughout a space • All things move toward equilibrium unless energy is added

  4. Diffusion • random movement of molecules • Involves molecules that are small enough to fit between the phospholipids • Molecules move from areas of higher concentration to areas of lower concentration • Example: perfume or food dye

  5. What affects the rate of diffusion?

  6. Osmosis • Diffusion of water across a semi-permeable membrane • Water moves from areas of high water concentration to areas of lower water concentration

  7. Osmotic Pressure

  8. Osmotic pressure • Hypertonic • [solute] inside cell < [solute] outside cell • Water moves out of cells • Cell collapses • Video

  9. Hypotonic [solute] outside cell < [solute] inside cell Water moves into cells Cell explodes Osmotic pressure

  10. Osmotic pressure • Isotonic: water levels are even inside and outside cell • [solute] outside cell = [solute] inside cell • Cell remains in balanced equilibrium

  11. Osmotic pressure • Cells attempt to prevent death due to osmotic pressure in a number of ways • Cell wall: rigid cell wall prevents membrane from rupturing (turgor pressure) • Pump out water: specialized organelles called vacuoles remove excess water • Bathe cells in blood: blood is fairly isotonic with cells

  12. Facilitated diffusion • Diffusion of specific molecules • Works with the aid of carrier proteins • Each carrier protein is molecule specific • Diffusion through ion channels • Facilitated diffusion flick

  13. Ion channels • allow passage of ions • ions are not lipid soluble so they need help • each specific to one kind of ion • may always be open or have “switches”

  14. Active Transport Active Transport

  15. Example: Na+/K+ pump • Cells pump Na+ out and K+ in • For every 3 Na+ that exit cell, 2 K+ enter • Ions affect shape of protein causing the appropriate channels to open and close. • Creates a charge across the membrane • Outside membrane has + charge • Inside membrane has a – charge • Allow for electrical conduction • Sodium potassium pump • Another Na+/K+ pump

  16. Active transport • Movement across a semi-permeable membrane that requires the use of energy • Used to move molecules against the concentration gradient • Video

  17. Active Transport • Endocytosis: movement of large molecules into cell by pinching off of the cell membrane • Pinocytosis: movement of water • Phagocytosis: movement of solids • Exocytosis: endocytosis in reverse • Endo and Exocytosis • ER and Golgi animation • Internal Transport

  18. Transport movies • More transport • Cotransport • The Inner Life of Cells • Inner Life with Narrative

  19. Evolution of multi-cellular organization The origin of eukaryotic cells The endosymbiont theory: Lynn Margulis

  20. Stromatolites are good evidence Stromatolites and their close cousins the thrombolites, are rock-like buildups of microbial mats that form in limestone- or dolostone-forming environments.

  21. Evolution of Multicellular Organisms

  22. Some Bacteria were more useful “confined and alive” than as food

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