Movement across the Cell Membrane

1. Movement across the Cell Membrane 2006-2007

2. Is this a passive or active process? Is this a passive or active process? Diffusion • Diffusion • movement from HIGH→LOW concentration • Down the concentration gradient What did it take to make the concentration gradient?

3. The concentration gradient stores potential energy • It takes energy to generate the gradient • The process is still considered passive 2006-2007

4. HIGH “The Bouncer” LOW Facilitated Diffusion • Diffusion through protein channels • highly specific • passive process what sort of molecules will use this process?

5. LOW “The Doorman” ATP HIGH Active Transport • Cells may need to move molecules against concentration gradient • conformational shape change transports solute from one side of membrane to other • protein “pump” • “costs” energy = ATP Once completed, where has the energy for the active transport gone?

6. ATP ATP Active transport • Many models & mechanisms antiport symport

7. ATP Getting through cell membrane • Passive Transport • Simple diffusion • nonpolar, hydrophobic molecules • HIGH → LOW concentration gradient • Facilitated transport • polar, hydrophilic molecules • through a protein channel • HIGH → LOW concentration gradient • Active transport • against concentration gradient • LOW → HIGH • uses a protein pump (requires ATP)

8. ATP Transport summary simplediffusion facilitateddiffusion activetransport

9. What about large molecules? • Moving large molecules into & out of cell • through vesicles & vacuoles • endocytosis • phagocytosis = “cellular eating” • pinocytosis = “cellular drinking” • exocytosis exocytosis

10. Endocytosis fuse with lysosome for digestion phagocytosis non-specificprocess pinocytosis triggered bymolecular signal receptor-mediated endocytosis

11. What about Osmosis? • Diffusion of water from HIGH concentration of water to LOW concentration of water • across a semi-permeable membrane Why does osmosis need a membrane?

12. water hypotonic hypertonic Concentration of water • Direction of osmosis is determined by comparing total solute concentrations • Hypertonic - more solute, less water • Hypotonic - less solute, more water • Isotonic - equal solute, equal water net movement of water

13. Hypotonic , Hypertonic, Isotonic How does sugar concentration lead to water movement?

14. Let’s watch the video Which way would water move if oil was added to the left side of the tube? 14

15. No problem,here KABOOM! Managing water balance • Hypotonic • Animal cell/protist cell problem? • Solutions? • Plant cells.... • turgid = full • cell wall protects from bursting freshwater

16. I willsurvive! I’m shrinking,I’m shrinking! Managing water balance • Hypertonic • Animal cells: • How can they adjust: • Take up water or pump out solutes. • plant cells • plasmolysis= wilt Why do people make beef jerky, and add syrup to preserve canned fruit? saltwater

17. I couldbe better… That’sperfect! Managing water balance • Isotonic • Animal cell problems: • none • solutes are equally concentrated on both sides of membranes • Plant cell problems • flaccid cells lose structure. balanced

18. Aquaporins • Water moves rapidly into & out of cells • evidence that there were water channels • protein channels allowing flow of water across cell membrane Peter Agre John Hopkins Roderick MacKinnon Rockefeller

19. Which way will water move? .05 M .03 M

20. Hey...watch this