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Membrane Structure and Function

Membrane Structure and Function. Cell membranes are selectively permeable Made mostly of proteins and phospholipids. Phospholipid. Membrane is a bilayer – hydrophilic heads pointing outwards, hydrophobic tails pointing inwards.

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Membrane Structure and Function

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  1. Membrane Structure and Function

  2. Cell membranes are selectively permeable • Made mostly of proteins and phospholipids.

  3. Phospholipid

  4. Membrane is a bilayer – hydrophilic heads pointing outwards, hydrophobic tails pointing inwards.

  5. The membrane is fluid because lipids and proteins can move laterally. • As temperatures drop, liquid membrane can solidify.

  6. Cholesterol found in membrane helps with fluidity of membrane.

  7. Two different types of proteins are found in membrane. • 1Peripheral proteins not in membrane, bound to surface of protein. • 2Integral proteins in membrane often spanning entire membrane.

  8. http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/M/MembraneProteins.gifhttp://users.rcn.com/jkimball.ma.ultranet/BiologyPages/M/MembraneProteins.gif

  9. Membrane helps keep cell’s shape. • Also aids in cell-to-cell recognition (ability of a cell to distinguish one type of neighboring cell from another)

  10. Diffusion - tendency for substance to spread out in open area. • Substances move from an area of high concentration to low concentration.

  11. No force acting upon it - passive transport.

  12. Difference in concentration - ions move from one area to other. • Solution with higher concentration solutes - hypertonic. • Solution with lower concentration solutes -hypotonic. • Equal concentrations - isotonic.

  13. http://www.biologycorner.com/resources/hypotonic.gif

  14. http://tlt.its.psu.edu/mto/bionutr/graphics/hypertonic.gif

  15. http://www.lucozadesport.com/lucozade/wwwroot/images/ch_1d6.gifhttp://www.lucozadesport.com/lucozade/wwwroot/images/ch_1d6.gif

  16. Cell placed in hypertonic solution – H20 rushes out of cell (cell shrinks). • Cell placed in hypotonic solution – H2O rushes into cell (cell swells).

  17. http://faculty.southwest.tn.edu/jiwilliams/plasmolysis.gif

  18. facilitated diffusion - diffusion of substance with help of transport protein • Gated Channels - channel proteins that can open and close depending on what substances what to pass through.

  19. In this case, the protein actually rotates to dump the materials to the inside of the cell.

  20. Active transport - materials need to be moved from Low to a High concentration. • Requires energy! • Example = sodium-potassium pump in animal cells

  21. http://www.sp.uconn.edu/~terry/images/anim/antiport.gif

  22. http://bioweb.wku.edu/courses/Biol131/images/neuronions.GIF

  23. Other types of Active Transport • Exocytosis - transport vesicle buds from Golgi apparatus and moves close to the cell membrane. • When membranes meet - fuse - material is let out to outside of cell.

  24. http://sparkleberrysprings.com/v-web/b2/images/lotc/exocytosis21a.jpghttp://sparkleberrysprings.com/v-web/b2/images/lotc/exocytosis21a.jpg

  25. Endocytosis - cell brings in macromolecules and matter by forming new vesicles from plasma membrane. • Membrane is inwardly pinched off and vesicle carries material to inside of cell.

  26. http://www.kscience.co.uk/as/module1/pictures/endoexo.jpg

  27. Type of endocytosis • 1Phagocytosis (“cell eating”) - cell engulfs particle by extending pseudopodia around it, packaging it in a large vacuole. • Contents of vacuole are digested when vacuole fuses with lysosome.

  28. 2Pinocytosis (cell drinking) - cell creates vesicle around droplet of extracellular fluid.

  29. 3Receptor-mediated endocytosis - specific in transported substances. • Extracellular materials bind ligands (receptors) - causes vesicle to form. • Allows materials to be engulfed in bulk (i.e. cholesterol in humans)

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