Plasma Membrane

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Three Forms of Transport Across the Membrane
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Active Transport

• moving upstream against the concentration
  gradient.
• B) Moving the Big Stuff in and out

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Active TransportPumps

• Requires energy or ATP
• Moves solutes from LOW to HIGH concentration
• Solutes move UP concentration gradient

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Pumps

• It takes a lot of energy to Swim upstream
• Likewise, it takes a lot of energy to move
  molecules UP a concentration gradient.
• This is Active Transport ATP Req.

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Pumps - Example

• Na (sodium ions) are pumped out
• K (potassium ions) are pumped in against
  strong concentration gradients.
• UPHILL
• Called Na-K Pump

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Sodium-Potassium Pump

• 3 Na pumped in for every 2 K pumped out
  creates a membrane potential
• Animation http//highered.mcgraw-hill.com/sites
  /0072495855/student_view0/chapter2/animation__how_
  the_sodium_potassium_pump_works.html

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Pump Review Compare with Facilitated Diffusion

• The use of Energy to move things in and out of
  the cell.
• ATP needed
• Similarities Both use membrane proteins

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Moving the Big StuffIn and Out

• Endocytosis INCOMING!!
• Exocytosis Making and Exit

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Endocytosis

• Membrane folds inward and creates a vesicle
  containing the particles

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Endocytosis 2 typesbased on size of material
moving in and out

• A) Pinocytosis Cell Drinking
• Pino Drink Cyto - cell
• Process by which cells engulf and incorporate
  droplets of fluid.
• Cells engulfing small particles and breaking them
  down.
• B) Phagosytosis Cell eating
• Phage eat Cyto cell
• Process by which cells engulf and incorporate
  large particles and break them down.

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Pinocytosis - Cell Drinking Most common form
of endocytosis.

• Materials dissolve in water to be brought into
  cell
• Cell forms an indentation

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Example of Pinocytosis
mature transport vesicle
pinocytic vesicles forming
Transport across a capillary cell (blue).
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Pinocytosis
Takes in dissolved molecules as a vesicle. Large
quantities
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Moving the Big Stuff
Large molecules move materials into the cell by
one of endocytosis.
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• Receptor-Mediated Endocytosis
• Needs to match the correct receptor ( usually a
  protein) before it can enter the cell
• Membrane forms a vesicle around the particles

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Receptor-Mediated Endocytosis
Some integral proteins have receptors on their
surface to recognize take in hormones,
cholesterol, etc. Animation http//www.sumanasinc.
com/webcontent/animations/content/endocytosis.html

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Receptor-Mediated Endocytosis
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Endocytosis Phagocytosis

• The engulfing and ingestion of bacteria or other
  foreign bodies by phagocytes
• LARGE PARTICLES

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Endocytosis Phagocytosis
Used to engulf large particles such as food,
bacteria, etc. into vesicles
Called Cell Eating
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Phagocytosis About to Occur
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Phagocytosis animation

• http//highered.mcgraw-hill.com/sites/0072495855/s
  tudent_view0/chapter2/animation__phagocytosis.html
  
• http//www.mydr.com.au/default.asp?Article4278

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• Phagocytosis
• Capture of a Yeast Cell (yellow)
• Using Membrane Extensions of an Immune System
  Cell (blue)

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Exocytosis The opposite of endocytosis is
exocytosis.
Inside Cell
Cell environment
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Exocytosis- moving things out.

• LARGE Molecules are moved out of the cell by
  vesicles that fuse with the plasma membrane.
• hormones are secreted this way
• nerve cells communicate with one another this
  way.

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Example Protein Release

• Vesicle moves up to and fuses with the membrane
• Proteins released outside the cell

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Exocytosis
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Review-- Three types of Active Transport

• Pump Membranes have proteins that pump certain
  compounds in and out against the concentration
  gradient. (e.g. sodium potassium pump)
• Endocytosis- cell membranes wrap around large
  particles (liquids or solids) and bring them into
  the cell. (white blood cells)
• Exocytosis- The cell membrane is used to expel
  large molecules. (vesicles from the golgi
  apparatus)