Transport In and Out of the Cell

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Transport In and Out of the Cell
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How Diffusion Works

• A little video
• Video

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Diffusion

• This is also known as passive transport and
  simple diffusion
• Passive transport is the movement of molecules
  down a concentration gradient from a region of
  higher concentration to lower concentration.
• Passive transport NEVER requires energy. (ATP)

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• The steeper the gradient, the faster the rate of
  diffusion.
• Humans obtain oxygen by simple diffusion across
  moist membranes in the air sacs in our lungs
  called alveoli.

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Diffusion

• It is also affected by
• Temperature- the higher the temp. the faster the
  molecules are moving
• Size of the Molecules- the bigger the molecule is
  the harder it is to pass through the membrane,
  possible not pass at all.

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How Osmosis Works

• http//highered.mcgraw-hill.com/sites/0072495855/s
  tudent_view0/chapter2/animation__how_osmosis_works
  .html

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Osmosis

• Osmosis- the diffusion of water (across a
  membrane)
• Water will move in the direction where there is a
  high concentration of solute (and hence a lower
  concentration of water.
• Salt is a solute, when it is concentrated inside
  or outside the cell, it will draw the water in
  its direction. This is also why you get thirsty
  after eating something salty.

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SALT SUCKS
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Isotonic Solution

• If the concentration of solute (salt) is equal on
  both sides, the water will move back in forth but
  it won't have any result on the overall amount of
  water on either side."ISO" means the same

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Hypotonic Solutions

• The word "HYPO" means less, in this case there
  are less solute (salt) molecules outside the
  cell, since salt sucks, water will move into the
  cell.
• The cell will gain water and grow larger. In
  plant cells, the central vacuoles will fill and
  the plant becomes stiff and rigid, the cell wall
  keeps the plant from bursting

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Hypertonic Solutions

• The word "HYPER" means more, in this case there
  are more solute (salt) molecules outside the
  cell, which causes the water to be sucked in that
  direction.
• In plant cells, the central vacuole loses water
  and the cells shrink, causing wilting.

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Hypertonic Solution

• In animal cells, the cells also shrink
• This is why it is dangerous to drink sea water -
  its a myth that drinking sea water will cause you
  to go insane, but people marooned at sea will
  speed up dehydration (and death) by drinking sea
  water.

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How Facilitated Transport Works

• A little video to show you
• http//highered.mcgraw-hill.com/sites/0072495855/s
  tudent_view0/chapter2/animation__how_facilitated_d
  iffusion_works.html

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Facilitated Diffusion

• Facilitated diffusion relies on special protein
  channels to assist in transporting specific
  substances across membranes.

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Facilitated Diffusion

• The proteins helps or facilitated the diffusion
  by changing shape and moving the molecule down
  the concentration gradient.
• This is very similar to diffusion in that both
  involve the movement of molecules down the
  concentration gradient with out energy
• They differ in the fact that this needs special
  proteins (carrier proteins)

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Dynamic Equilibrium

• When the rates of the forward and reverse
  reactions are equal. The system is dynamic
  because individual molecules react continuously.
  It is at equilibrium because no net change
  occurs.

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• All of the previous require
• NO ENERGY or
• ATP

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Active Transport

• This is the movement of molecules against a
  gradient.
• This is like driving a car in traffic, going in
  the wrong direction. It takes more energy to go
  against the path then it does to go with the
  traffic.
• This requires ENERGY, ATP.

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Active Transport

• Active transport occurs with the aid of carrier
  proteins, which are commonly known as pumps.
• The cell maintains the proper balance of
  substances it needs due to this active transport.
• This helps maintain homeostasis.

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Endocytosis

• This is the process by which a cell surrounds a
  substance in the outside environment, enclosing
  it in a portion of the plasma membrane.
• The membrane pinches off and leaves the substance
  inside the cell and the resulting vacuole, with
  the contents moves to the inside of the cell.
• http//www.coolschool.ca/lor/BI12/unit4/U04L05/end
  ocytosis_final.html

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Exocytosis

• This is the active release of molecules from a
  cell. This is the opposite of endocytosis.
• The cell uses this to get rid of wastes and to
  secrete substances, for example hormones,
  produced by the cell.
• http//www.coolschool.ca/lor/BI12/unit4/U04L05/ex
  ocytosis.html

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Pinocytosis

• This is also called cell drinking.
• This is the uptake of large dissolves molecules.
• The plasma membrane surrounds small/tiny
  particles and encloses them in a vesicle.
• http//student.ccbcmd.edu/gkaiser/biotutorials/eu
  struct/pinocyt.html

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Phagocytosis

• This is the engulfing of large particles or even
  small organisms by pseudopods.
• The cell membrane wraps around the particles and
  encloses them forming a vacuole.
• This is the way that the human white blood cells
  take up bacteria.
• PAC-MAN

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Receptor-Mediated Endocytosis

• This enables cells to take up large amounts of
  very specific substances.
• The extra cellular substances bind to specific on
  the cell membrane and are brought into the cell.
• Example This is the way that body draws the
  cholesterol into the blood.

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• Membrane pumps carry particles or ions across the
  membranes AGAINST the gradient (needs
  energy/ATP).
• The sodium-potassium pump is an example of this

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Sodium - Potassium Pumps

• This is one of the most common active transport
  pumps.
• This is found in the plasma (cell) membrane of
  animal cells.
• This maintains the levels of Sodium (Na) and
  Potassium (K) in and out of the cell
• This protein pump uses the energy in order to
  transport 3 sodium ions out of the cell while
  moving 2 potassium ions into the cell.

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• http//highered.mcgraw-hill.com/sites/0072495855/s
  tudent_view0/chapter2/animation__how_the_sodium_po
  tassium_pump_works.html

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