Diffusion and Osmosis

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Diffusion and Osmosis

• Diffusion Section 6.2
• Osmosis Section 8.1

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Biology 10/29/13
Mrs. Turgeon

• DO NOW
• Get out your cell lab worksheet
• In your notes Describe one difference between an
  animal cell and a plant cell.
• AGENDA
• Finish part F of cell lab as a group
• Take notes on diffusion and osmosis
• REMINDERS
• Science Club today after school, room 312!
• Science Fair judges still needed

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Objective

• SWBAT explain how molecules are transported
  across the cell membrane.

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Diffusion

• The net movement of molecules from an area of
  higher concentration to an area of lower
  concentration.

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Diffusion

• Diffusion results because of the random movement
  of particles.
• Three key factors concentration, temperature,
  pressure affect the rate of diffusion.
• Equilibrium is reached when there is an even
  distribution of solute molecules

(water)
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Osmosis

• The diffusion of water across a selectively
  permeable membrane.

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Osmosis

• In a cell, water always moves to reach an equal
  concentration on both sides of the cell membrane.

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Osmosis

• The direction of osmosis depends on relative
  concentrations of dissolved particles on the two
  sides of the membrane.

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Direction of Osmosis

• Isotonic Solution
• concentration of dissolved particles outside and
  inside the cell are equal.
• there will be no net movement of water.
• water diffuses into and out of the cell at equal
  rates.

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Direction of Osmosis

• Hyptertonic Solution
• concentration of dissolved particles outside the
  cell is higher than in the cytosol.
• water will diffuse out of the cell.

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Direction of Osmosis

• Hypotonic Solution
• concentration of dissolved particles outside the
  cell is lower than in the cytosol.
• water will diffuse in to the cell.

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How Cells deal with Osmosis
Chapter 5

• To remain alive, cells must compensate for the
  water that enters the cell in hypotonic
  environments and leaves the cell in hypertonic
  environments.

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Passive Transport

• Movement of molecules across the cell membrane
• Does NOT require energy
• Examples diffusion and osmosis

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Facilitated Diffusion

• Passive transport of materials across the cell
  membrane using transport proteins.
• Examples
• Carrier Proteins
• Ion Channels

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Facilitated Diffusion
Chapter 5
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Chapter 5
Active Transport

• Movement of particles across the cell membrane
  against the concentration gradient
• (lower concentration ? higher concentration)
• Requires ENERGY!!!
• Example
• Carrier proteins, endocytosis, exocytosis

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Chapter 5
Active Transport

• Endocytosis
• Cells ingest external materials by folding around
  them and forming a pouch.
• Engulfs bacteria, food etc.

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Chapter 5
Active Transport

• Exocytosis
• Excretion of materials from a cell.
• Expels wastes, hormones etc.