Cellular Transport Osmosis and Diffusion

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Cellular TransportOsmosis and Diffusion!

• Ch. 8
• See how it flows!
• Mrs. Andrianopoulos

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Diffusion

• Mixing of two substances by the random motion of
  molecules
• Movement of molecules occurs from high
  concentration to low concentration until the
  molecules of the substance are equally
  distributed.

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REMEMBER

• H, O, P, N etc are all called what?
• Atoms
• Molecules have a tendency to move from areas of
  high concentration to areas of low concentration
• Solvent is water
• Solute is anything dissolved in water
• Solution is a solvent plus a solute

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Things to consider

• If you were in college.
• You were at a party.
• You were trying to find a date to go with to the
  fraternity/sorority party
• You were in a room of the house that was
  predominantly a party of the same sex
• The other room was predominantly the opposite sex
• The tendency is to go to the other room
• To move from a high concentration to an area of
  low concentration
• That is what the molecules do

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DIFFUSION
College Party in same sex rooms
College Party in co-ed rooms
male student
female student
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DIFFUSION
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Dynamic Equilibrium
Once the water and sugar molecules have evenly
mixed and have an equal concentration they have
reached dynamic equilibrium. The atoms are
continuously moving and bouncing off each other,
but the concentration stays the same.
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IMPORTANT DEFINITIONS

• DIFFUSION movement of particles from higher
  concentration to lower concentration
• Dynamic Equilibrium the particles continuously
  move but there is equal concentration on both
  sides of the membrane

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Osmosis

• OSMOSIS diffusion of water (only water!) across
  a selectively permeable membrane
• Notice the word diffusion in the definition
• Osmosis is a specialized type of diffusion
• In a cell, water always tries to reach an equal
  concentration on both sides of the membrane!

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OSMOSIS
The water molecules want to move to create
dynamic equilibrium
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Concentration Gradient

• The unequal distribution of particles
• Remember being in a room in a house were it is
  predominantly the same sex and you need a date
• This actually controls osmosis

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What controls OSMOSIS?

• A concentration gradient (unequal distribution of
  particles on each side of a membrane) p. 202

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During osmosis, only water diffuses across the
selectively permeable membrane.
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OSMOSIS
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Gotta love the Greeks!

• ISOS
• equal
• HYPO
• less
• HYPER
• more

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ISOTONIC SOLUTIONS!

• Concentration of dissolved substances in solution
  is the same as concentration of dissolved
  substances inside the cell.
• Water inside cell is equal to water in solution.
• Cells in isotonic solution do not experience
  osmosis and retain their normal shape.
• EX Immunizations are isotonic solutions so they
  do not damage the cells by gain or loss of water.

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HYPOTONIC SOLUTIONS!

• Concentration of dissolved substances is lower in
  the solution outside the cell than concentration
  inside the cell.
• There is more water outside the cell than inside.
• Therefore, there is more solute inside the cell
  than outside.
• Osmosis occurs and water moves through the cell
  membrane into the cell.

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Hypotonic Solutions

• Hypo means less
• When referring to a hypotonic solution you are
  referring to the amount of SOLUTE outside versus
  inside
• Therefore you have LESS SOLUTE OUTSIDE VERSUS
  INSIDE the cell
• Where does the solute want to move then?
• To the outside of the Cell
• Where does the water want to move?
• To the inside the Cell

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Examples of Hypotonic Solutions

• Grocers spray mist of water over veggies to keep
  them looking crisp
• In animal cells, the pressure inside cell
  increases causing the cells to swell and
  sometimes burst!
• In plant cells, the rigid cell wall prevents
  bursting, but the cells become more firm.
• CUCUMBERS IN THE MIST!

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HYPERTONIC SOLUTIONS!

• Concentration of dissolved substances outside
  cell is higher than concentration inside cell.
• There is more water inside cell than outside.
• Cells in hypertonic solutions experience osmosis
  in which water moves through membrane to outside
  of cell.

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Hypertonic Solutions

• Hyper means more
• When referring to a hypertonic solution you are
  referring to the amount of SOLUTE outside versus
  inside
• Therefore you have MORE SOLUTE OUTSIDE VERSUS
  INSIDE the cell
• Where does the solute want to move then?
• To the Inside of the Cell
• Where does the water want to move?
• To the outside of the Cell

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Examples of a Hypertonic Solution

• In animal cells, the pressure decreases and the
  cells shrivel.
• In plant cells, membrane and cytoplasm shrink
  away from cell wall and plant wilts.
• Dont be so SALTY!

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Passive Transport Mosey on through

• Passive transport is what it sounds like!
• Molecules pass through the membrane by diffusion
  requiring no extra energy.
• The molecules just mosey on through the membrane.
• Ex Some of the molecules that move by passive
  transport are water and lipids

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Passive Transport
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Passive Transport
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Facilitated Diffusion Help them out a bit!

• Remember those transport proteins in the
  phospholipid bilayer? Heres where they fit in!
• Facilitated diffusion passive transport across
  membrane with help of transport proteins.
• Ex Facilitated diffusion is used to move sugars
  and amino acids across membranes.

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Active Transport ENERGY REQUIRED!

• Active transport is the movement of materials
  through a membrane across a concentration
  gradient.
• This requires energy to counteract the movement
  of diffusion from high to low concentrations!

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How does it work?

• Transport protein called carrier protein binds
  with particle that is going to be transported.
• Because of its specific shape, the carrier
  protein can bind to the particle and with some
  energy, it can move through the membrane.
• Once the particle is released, the protein
  returns to its original shape.
• Active transport allows a particle to move into
  or out of a cell--against a concentration
  gradient. (So it works the opposite way of
  diffusion going from low concentration to high
  concentration).

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How carrier proteins work!
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Active Transport
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Active Transport
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Cellular Transport
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What about the big boys?

• ENDOCYTOSIS cells surrounds and takes in
  material from environment by engulfing the
  material! YUMMY!
• EXOCYTOSIS cells expel materials from cell, such
  as waste or indigestible particles. GROSS!
• Both endo and exocytosis are moving large masses
  of material and require energy (ACTIVE TRANSPORT!)

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Endocytosis
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Exocytosis