Transport Across A Cell Membrane

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Transport Across A Cell Membrane

• pp. 185-9

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Demonstrations
Observations Explanation
Peppermint oil
Iodine alcohol
Cornstarch bag
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Diffusion

• Molecules move from areas of high concentration
  to areas of low concentration

• What is concentration?
• The amount of something (particles) in a given
  solution (volume)

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How does diffusion happen?

• Random movement of molecules
• Does NOT require energy
• Equilibrium occurs when the concentration is the
  same throughout
• Do you think the particles continue to move after
  equilibrium is reached?

EQUILIBRIUM
HIGH CONC
LOW CONC
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Osmosis

• The diffusion of water through a selectively
  permeable membrane
• Which direction?
• Does it require energy?

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Terms comparing concentration across a membrane

• Hypertonic
• Hypotonic
• Isotonic
• Question How do cells compare to their
  environment?

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Animal cells

• Animation of red blood cells
• Shrink swell (sometimes burst) in response to
  their environment
• In the body, our cells are bathed in isotonic
  fluids protected by our skin

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Plant cells bacteria

• Animation of Elodea
• Plant cells have cell walls that prevent them
  from shrinking swelling
• Plant cells also have large central vacuoles that
  store excess water
• Why the rainstorm on veggies at the grocery
  store?
• How does Penicillin work?

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Protists

• Animation of Paramecium
• Pump excess water out of contractile vacuoles

http//programs.northlandcollege.edu/biology/Biolo
gy1111/animations/transport1.html
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Animations

• Passive vs. active transport
• Why does diffusion occur?
• Osmosis
• Molasses demo
• Facilitated diffusion
• Active transport
• Phagocytosis