Diffusion and Osmosis

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Diffusion and Osmosis
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Diffusion

• Molecules in solution tend to slowly spread apart
  over time. This is diffusion.

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Diffusion is Concentration Dependant

• Diffusion is the net movement of particles from a
  region of higher to lower concentration down a
  concentration gradient.

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Osmosis

• ALL compounds undergo diffusion.
• Water also diffuses, however, the water diffusion
  is not evident unless it crosses a membrane.
• Osmosis is the diffusion of water across a
  semi-permeable membrane.
• Since cells have membranes, osmosis is important
  to cells

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Membranes and Osmosis

• Tank w/ semi-permeable membrane water may pass,
  solute (particles) cant

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Osmotic Terminology

• Hypertonic
• Hypotonic
• Isotonic

Refer to the solute concentration
Solution solute water
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Animal Cells and Osmotic Pressure
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Plant Cells and Osmotic Pressure

• In plants, hypotonic solutions produce osmotic
  pressure that produces turgor pressure
• Turgor means tight or stiff owing to being very
  full
• Keeps plant upright in hypertonic conditions
  plants wilt

Vacuole fills
Vacuole shrinks
Hypertonic
Hypotonic solution
Hypertonic
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In multicellular organisms, diffusion transports
substances across small distances between the
blood and the interstitial fluid and between the
interstitial fluid and the cells
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The exchange of CO2 between body cells and RBCs
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