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Cell Transport

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									Cells and Cell Transport

      Pre-AP Biology
           Cell Structure
 Despite differences in size and
  shape, certain structures are
  common to almost all cells.
 –Cell membrane- surrounds the cell
 –Nucleus or a concentrated area
  where the DNA is contained
 –Cytoplasm- jelly in the cell
     Two Types of Cells
 Prokaryotic- Cells that do not
  have a membrane bound
  nucleus or organelles.
 Only Bacteria
        Two Types of Cells
 Eukaryotic- Cells that have a
  membrane bound nucleus.
 Everything but
  bacteria.
     Transport Across the Cell
           Membrane
   All cells exist in a liquid environment
   This liquid environment makes it easier
    for materials such as food, water, and
    oxygen to move in and out of a cell.
   Cell membrane is selectively permeable
    – some materials can pass and others
    cannot.
           Cell Membrane
   Cell membrane is made of phospholipids.
           Cell Membrane
   Phospholipids align to form a
    phospholipid bilayer with hydrophilic
    heads on the outside and hydrophobic
    tails on the inside.
           Cell Membrane
   Molecules that can pass through cell
    membrane are small, hydrophobic, or
    uncharged.
   Molecules that cannot go through easily
    are large, hydrophilic, or charged and
    have to be let in another way
           Cell Membrane
   4 ways that molecules get across the
    cell membrane:
    - diffusion
    - osmosis
    - facilitated diffusion
    - active transport
                  Diffusion
   Definition: molecules moving from an area
    of high concentration to an area of low
    concentration until reaching an equilibrium.
   Molecules have kinetic energy which
    causes them to bounce around.
   Some molecules can pass through the cell
    membrane by diffusion.
                  Osmosis
   Definition: the diffusion of water across a
    selectively permeable membrane
   Water moves until the concentration of
    molecules on
    either side of a
    selectively
    permeable
    membrane has
    reached an
    equilibrium.
                Osmosis
   The force exerted by osmosis, or
    osmotic pressure, tends to move water
    across membranes from a more dilute
    solution into a more concentrated
    solution.
   Osmotic pressure can cause serious
    problems for a cell.
          Isotonic solution
   In a solution that is just as salty as
    inside of the blood cells (0.9% NaCl).
         Hypotonic solution
   In a solution that is less salty than the
    inside of the blood cells (0.65% NaCl).
        Hypertonic solution
   In a solution that is saltier than the
    inside of the blood cells (1.01% NaCl).
    Other Types of Transport
   We are going to look at ways to
    transport those large, charged, and
    hydrophilic molecules that have to be
    carried across the cell membrane.
       1. Facilitated Diffusion
   No ATP energy required.
   Molecules move down a concentration
    gradient (from high to low).
   Uses a transport protein.
          2. Active Transport
   Requires ATP energy.
   Pumps particles against concentration
    gradient (low to high).
   Keeps important ions and nutrients in cells
    (ion pumps).
        2. Active Transport
   Cotransport – 2 materials passing
    through the membrane.
   Na+ - K+ pump – conducts nerve
    impulses in animal cells.
           3. Endocytosis
   Cell takes in molecules by forming
    vesicles around molecules with the cell
    membrane.
              4. Exocytosis
   Vesicles from the ER or
    Golgi fuse with cell
    membrane and dump
    the contents outside of
    the cell.
   Secrete products into
    blood, like insulin from
    pancreatic cells.

								
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