Transport Through Membranes

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Transport Through Membranes
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Passive VS Active

• Passive no added energy required
• Passive moves materials from areas of high
  concentration to areas of lower concentration
• Active requires ATP energy
• Can move substances from low to high
  concentrations

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Passive Diffusion

• Diffusion movement of any substance from area of
  high concentration to lower concentration
• Facilitated Diffusion moves substance with help
  of non channel carrier protein does not require
  energy to change shape of protein
• Used for substances that cannot cross the
  membrane large or charged

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Passive Osmosis

• Special type of diffusion
• Only water and only through partial/selectively
  permeable membrane
• May pass through protein channels called
  aquaporins
• Hyper-osmotic solution has higher concentration
  of solutes than hypo-osmotic solution
• Water moves from hypo-osmotic solution to
  hyper-osmotic solution through membrane until
  equilibrium of solute concentration is reached

5
Active Transport

• Work required thus ATP
• Move against concentration gradient
• Maintain interior concentrations different from
  exterior
• Potassium pumped in and Sodium pumped out
• Protein channel pump required

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Sodium Potassium Pump

• Specific protein binds 3 intracellular sodium
  ions
• Binding induces phosphorylation by ATP
• Phosphorylation cause shape change
• Sodium ions expelled from cell
• 2 extracellular potassium ions bind to another
  part of protein pump causing release of phosphate
  group producing an ADP from ATP
• Loss of phosphate returns protein to original
  shape and releasing the potassium into cell