Cellular transport

About cell membranes and transport

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  • Created by: Sophie
  • Created on: 25-10-11 11:55

Cell membranes

  • All cells have a cell membrane
  • It controls what enters and exits the cell to maintain an internal balance called homeostasis
  • Provides protection and support for the cell
  • Structure of cell membrane = lipid bilayer
  • Phosphate head is polar (water loving)
  • Fatty acid chains non-polar (water fearing)
  • Proteins are embedded in membrane
  • Have ppores which are slectivley permeable: allows some molecules in and keeps other mollecules out.(http://t2.gstatic.com/images?q=tbn:ANd9GcTFpPqD2cqzskwlwlBDwwBlkRR-njJ_l6dTtn2uHWiw0tv3dFA9)
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Types of cellular transport-passive transport

Passive transport

  • Cell doesn't use energy (e.g diffusion, facilitated diffusion, osmosis)
  • Molecules move randomly
  • Molecules spread out from a high concenttration to a low concentration


  • Random movement of particles from high to low concentration
  • Diffusion continues untill all molecules are evenly spread and equilibrium is reached. (NOTE: molecules will still move, just evenly)

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Passive transport continued

Facilitated diffusion

  • Diffusion of specific particles through transport proteins found in the membrane.
  • Transport larger or charged molecules


  • Diffusion of water through a partial permeable membrane.
  • From high water potential to a low water potential
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Types of cellular transport-active transport

Active transport

  • Uses energy
  • movement from a low concentration to a high concentration

Protein pumps

  • Transport proteins that require energy to do work (e.g sodium/potassium pumps are important in nerve responses)


  • Taking bulky material into a cell
  • In-folds around the "food" particle and forms food vacuole and digests food.


  • Forces material out of cell in bulk. Cell changes shape which requires energy.
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Hypotonic solution, Hypertonic solution and Isoton

Hypotonic: the solution has a lower concentration of the solutes and a higher concentration of water than inside the cell. (Low solute; high water)

RESULT: Water moves from the solution to inside the cell; cell swell and bursts (cytolysis)

Hypertonic: The solution has a higher concentration of solutes and a lower concentration of water inside the cell (High solute;low water)

RESULT:Wter moves from inside the cell into solution; cell shrinks (plasmolysis)

Isotonic:The concentration of solutes in the solution is equal to the concentration of solutes inside the cell

RESULT: Water moves equally in both direction and cell remains sam size. (Dynamic equilibrium)

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