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Exchange with the Environment

Exchange with the Environment. Cell Transport. Cell Processes. For a cell to survive, it must get nutrients and water. It must also get rid of wastes How can the cell get materials in and out through the cell membrane?. Cell membrane. Made up of a phospholipid bilayer and several proteins

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Exchange with the Environment

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  1. Exchange with the Environment Cell Transport

  2. Cell Processes • For a cell to survive, it must get nutrients and water. It must also get rid of wastes • How can the cell get materials in and out through the cell membrane?

  3. Cell membrane • Made up of a phospholipid bilayer and several proteins • Phospholipid: • Hydrophillic phosphate head • Hydrophobic fatty acid tail Image from: http://academic.brooklyn.cuny.edu/biology/bio4fv/page/phosphb.htm

  4. Cell membrane

  5. Cell membrane: Proteins • Integral Proteins • Embedded in lipid bilayer • Receptor proteins and transport proteins • Transmit signal or materials into/out of the cell • Peripheral Proteins • Only on one side of membrane • Some act as enzymes • Some act as cell markers

  6. Fluid mosaic model of cell membrane • Phospholipid bilayer acts as a fluid • Lipids and proteins can move in the layer • Sterols (including cholesterol) are used to help keep membrane structure

  7. Cell membrane

  8. Cell Membrane

  9. Diffusion • The movement of particles from an area of high concentration to an area of low concentration down the concentration gradient • Occurs outside of cells and across cell membranes

  10. Diffusion Picture from: http://hyperphysics.phy-astr.gsu.edu/hbase/kinetic/diffus.html

  11. Osmosis • The diffusion of water across a cell membrane • If solution outside a cell has more water than the cell then water will move into the cell

  12. Osmosis Image from: http://hyperphysics.phy-astr.gsu.edu/hbase/kinetic/diffus.html#c3

  13. Movement of small particles • Not all particles are able to slip through a cell membrane through diffusion • Example: sugars and starches aren’t small enough to move between the phospholipid molecules

  14. Types of solutions • Isotonic • Has same concentration as a cell, the cell neither loses nor gains water • Hypotonic • Has less concentration than cell, cell gains water

  15. Types of solutions • Hypertonic • Has more concentration than cell, cell loses water

  16. Osmosis in cells • Paramecia • Control water flow by using a contractile vacuole • Collect excess water and pump it out of the cell • Plant cells • Live in hypotonic environment • Survive because of cell wall • Pressure of water against cell wall: turgor pressure • Too much water leaves the cell: plasmolysis • Water storage in Central Vacuole

  17. Transport of particles • Some particles have to go through “doorways” to enter the cell • Because they are too large or not soluble through cell membrane • These “doorways” are protein channels • These proteins are carrier proteins

  18. Facilitated Diffusion • Diffusion of particles through protein channels in a cell membrane • Particles move from high concentration to low concentration • Example: glucose and salts • Does NOT require energy

  19. Image from: http://www.bios.niu.edu/sims/metabolism/metabolism1.htm

  20. Ion Channels • Allow ions to move across the cell membrane • Specific to specific ions • Some are “gated”

  21. Active transport • Movement of particles against the normal direction of diffusion • Particles move from LOW concentration to HIGH • Requires energy from the energy molecule ATP • Example: sodium/potassium pump

  22. Image from: http://www.cat.cc.md.us/courses/bio141/lecguide/unit1/prostruct/images/u1fig7a.jpg

  23. Image from: http://www.sp.uconn.edu/~terry/images/anim/antiport.gif

  24. Moving larger particles • Endocytosis • Cell membrane surrounds a particle, and encloses it in a vesicle • Phagocytosis • When large particles are taken in by endocytosis • Pinocytosis • Transport of fluids or solutes

  25. Image from: http://www.sirinet.net/~jgjohnso/endocytosissmall.jpg

  26. Endocytosis Image from: http://www.sp.uconn.edu/~bi107vc/images/cell/clathrin.jpg

  27. Exocytosis • Used to remove large particles from the cell • Vesicles formed at the ER or Golgi move to the cell membrane for release

  28. Exocytosis Image from: http://www.sirinet.net/~jgjohnso/exocytosis.jpg

  29. Image from: http://cellbio.utmb.edu/cellbio/end7.jpg

  30. Modeling the cell membrane

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