Understanding Homeostasis: Passive and Active Transport Mechanisms in Cells

1. Maintaining Homeostasis Passive and Active Transport

2. Lesson Objectives • Understand how equilibrium is established as a result of diffusion. • Distinguish between diffusion and osmosis.

3. Cellular Membrane • Membrane: function is to control what enters and exits the cell • Selectively permeable

4. Homeostasis • All living cells exists in a liquid environment • Internal conditions need to remain constant • Homeostasis • Equilibrium=everything is balanced • Maintain homeostasis by regulating movement of molecules across the membrane • Passive Transport (no energy required) • Active Transport (energy required)

5. Passive Transport: Diffusion • Movement of materials across the cell membrane without using energy • Diffusion: • Movement of material/molecules from an area of high concentration to an area of low concentration • Concentration Gradient

6. Passive Transport: Osmosis • When water diffuses across the cell membrane • http://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter2/animation__how_osmosis_works.html

7. Effects of Osmosis on Cells Hypotonic: • Lower solute concentration outside of the cell • Water moves into the cell • Cell swells Hypertonic: • Higher solute concentration outside of the cell • Water moves out of the cell • Cell Shrinks Isotonic: • Concentration is the same inside and out • Water moves in and out

10. How does water move? “Salt Sucks”

11. How does water move? “Salt Sucks”

12. How does water move? “Salt Sucks” v v

13. Osmosis In Nature • Cytolysis: in a hypotonic solution red blood cells will continue to swell until they burst • Penicillin killing bacteria • Contractile Vacuole: organelle in protist cells that pumps excess water out • http://www.youtube.com/watch?v=pahUt0RCKYc&feature=related • Turgor Pressure: water pressure placed on the cell wall to give plant cell its shape • Plants wilting if solution is hypertonic • Don’t drink salt water • Diarrhea • Something in stools that is drawing out the water

14. Facilitated Diffusion • Movement of particles from higher concentration to lower concentration • Large molecules may require “help”, they use carrier proteins • Nervous system uses Na and Ca pumps

15. Lesson Objectives • Distinguish between passive and active transport. • Explain how sodium-potassium pumps operate. • Compare and contrast endocytosis and exocytosis.

16. Active Transport Active Transport Passive Transport: down concentration gradient

17. Active Transport Passive Active

18. Active Transport • Requires energy to move molecules up their concentration gradient • Low concentration to high concentration • Sodium-Potassium Pump • Exocytosis • Endocytosis

19. Cell Membrane Pumps • Requires a carrier protein • 3 Na-2 K • Requires energy • http://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter2/animation__how_the_sodium_potassium_pump_works.html

20. Endocytosis • Phagocytosis • Pinocytosis

21. Exocytosis