Diffusion

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Diffusion and Osmosis
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Osmosis

• Osmosis is the diffusion of free water
  molecules
• Water moves from high to low concentrations
  across a partially-permeable membrane
• until they are evenly spread out

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Selectively permeable (partially-permeable )

• Cell membranes are selectively permeable
• Some solutes cross the membrane freely, some
  cross with assistance, and others do not cross at
  all.

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Partially-Permeable Membranes

• A partially-permeable membrane will allow
  certain molecules to pass through it, but not
  others.

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Diffusion

• Particles in a liquid or gas spread out
• from areas of high concentrationto areas of
  low concentration
• until the particles are evenly spread out.

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• Diffusion occurs because the particles in gases
  and liquids are moving.

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When two environments are isotonic, the total
molar concentration of dissolved solutes is the
same in both of them.

• 4. Hypotonic Concentrations of dissolved solutes
  are less outside the cell than inside, the
  concentration of water outside is correspondingly
  greater.
• 5. Isotonic When two environments are isotonic,
  the total molar concentration of dissolved
  solutes is the same in both of them.
• 3. Hypertonic Concentrations of dissolved
  solutes are greater outside the cell, the
  concentration of water outside is correspondingly
  lower.

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More free water molecules on this side of membrane
Free water molecules diffuse in this direction
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Equilibrium

• Diffusion continues until all molecules are
  evenly spaced (Once this happens Equilibrium is
  reached)
• Note molecules will still move around but stay
  spread out.

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