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					The Cell Membrane
Active and Passive Transport
                              Goals for Today
• Know the structure of the Cell
  membrane
  – Selectively Permeable
• Understand the concept of Diffusion
• Passive Transport
  – Simple Diffusion
  – Facilitated Diffusion
  – Osmosis
• Active Transport
  – Na+ K+ pumps
  – Endocytosis, Exocytosis
                 Cell Membrane
• Phospholipid bilayer: hydrophilic heads and
  hydrophobic tails
• Semi-permeability
• Transport proteins (passive transport channels)
• Ion pumps (active transport pumps
• Receptor proteins (neurons, hormones, immune
  system)
• Carbohydrate chains ( identification cards)
 Question – you should be asking yourself

• What is another name for the cell
  membrane?
• What is its function?
• What is composed of? Explain with a
  drawing.
• What does the term passive mean?
  Passive transport?
                  Passive Transport
• Diffusion – The Movement of particles from an Area
              High Concentration to an area of Low
              Concentration until an equilibrium has
              been reached.
• Concentration Gradient
  High Concentration to a Low Concentration
• 1) simple diffusion (molecules are small enough and
  soluble can pass directly through the lipid bilayer)
• 2) facilitate diffusion – need transport proteins
  (molecules are either to large or can’t pass through
  the lipid bilayer themselves)
• 3) osmosis – molecules can’t pass through lipid
  bilayer at all, but water can(movement of water)
• Depends on molecule size, lipid solubility, and
  concentration gradient
                     Osmosis




•Isotonic (concentrations of 2 settings are equal),
•hypertonic (cell placed in higher concentration),
•hypotonic solution (cell placed in lower concent.)
Hypertonic, Hypotonic or Isotonic???
Osmotic Pressure
            Active Transport

• Molecules move against the
  concentration gradient
 Low Concentration to a High Concentration

• Requires energy
• Na+-K+- (ATPase) pump
Na+/K+ Pump
          Active Transport

• Endocytosis (pinocytosis,
  phagocytosis):
• Exocytosis: release of materials
  (wastesproteins, hormones,
  neurotransmitters- release of
  proteins, hormones,
  neurotransmitters)
Endocytosis

				
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posted:5/24/2012
language:English
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