What are the differences between osmosis and diffusion?

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• What are the differences between osmosis and
  diffusion?
• What regulates diffusion and osmosis?
• What is the difference between osmolarity and
  osmolality?
• Iso-osmotic, hyper-osmotic and hypo-osmotic
• Isotonic, hypertonic and hypotonic?
• Be able to do a calculations of solutions (A vs.
  B)
• Molarity, millimolarity, osmolarity,
  milliosmolarity, water movement
• Which solution is Isotonic, hypertonic and
  hypotonic?

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MOLARITY VS MOLALITY

• One mole of a solute (MW) dissolved and made up
  in 1 liter of solvent (1000ml) is a 1M (one molar
  solution)
• One mole of a solute (MW) dissolved in 1 kilogram
  of solvent (1000g) is a 1m (one molal solution)

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MOLARITY/MOLALITY

• 1M One molar
• 1m One molal
• 1M 1000mM (millimoles)
• 1m 1000mm (millimolals)
• Assumed equal in all our examples!!!

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OSMOTIC PRESSURE

• The greater or larger the solute of a solution,
  the greater the osmotic pressure
• Osmotic pressure is measured is measured as
  Osmolarity or Osmolality
• (remember equal for us because everything
  dissolves completely in our solvent (water)

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OSMOTIC PRESSURE UNITS

• 1 Osm 1 osmole
• 1 Osm 1000 mOsm (milliosmoles)
• Same units used for Osmolality and Osmolarity!!!

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OSMOLARITY/OSMOLALITY

• Depends on the ratio of solute to solvent
• The higher the solute the
• higher the osmotic pressure
• BUT
• MAJOR DIFFERENCES BETWEEN
• SALTS AND SUGARS!!

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• SUGARS (glucose, sucrose etc.)
• Do NOT ionize (dissociate) when they
• are dissolved in water!!
• IM glucose ------gt 1Osm
• (placed in H20)

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• SUGARS (glucose, sucrose etc.)
• Do NOT ionize when they
• are dissolved in water!!
• IM glucose ------gt 1Osm
• (placed in H20)
• SALTS (NaCl, CaCl2 etc.) DO ionize or
• dissociate!!
• IM NaCl ------gt 1 Osm Na plus 1 Osm Cl-
• (placed in H20)
• (each exert own osmotic pressure) 2 Osm

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OSMOSIS

• Osmosis is the movement of water (solvent)
  across a semi-permeable membrane from a region of
  high solvent concentration low solute to a
  region of low solvent high solute.

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OSMOSIS

• Water is pulled across a semi-permeable
  membrane to the side that has the highest osmotic
  pressure or is the most
• osmotically active solute

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Effects of Solutions of Varying Tonicity

• Isotonic solutions with the same solute
  concentration to each other
• Hypertonic solution having greater solute
  concentration to the other
• Hypotonic solution having lesser solute
  concentration to the other