The Selectively Permeable Membrane Lab

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• The Selectively Permeable Membrane Lab

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Problem

• What does selectively permeable mean?

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Hypothesis

• If iodine and starch are placed on opposite sides
  of a membrane, then the membrane will be
  selectively permeable by__________________________
  ____

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Procedure

1. Measure 100 mL of iodine solution in a beaker.
2. Put 40 mL starch into a plastic bag which will
   act as a membrane.
3. Tie the bag closed with a string.
4. Place the bag into the beaker of iodine.

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Initial Drawing of Cell
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Homeostasis Maintaining a Balance

• Cells must keep the proper concentration of
  nutrients and water and eliminate wastes.
• The cell membrane is selectively permeable.

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Structure of the Plasma Membrane

• Lipid bilayer two sheets of lipids
  (phospholipids).
• Found around the cell.
• Embedded with proteins and cholesterol molecules.

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Whats a Phospholipid?

• Its a pair of fatty acid chains and a phosphate
  group attached to a glycerol backbone.

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cytoskeleton
cholesterol
carbohydrate chains
membrane protein
outside the cell
interior of cell
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Getting into a cell (or out of it)

• Passive transport some particles are so small
  they can move into or out of a cell with no help
  and no energy need.
• These particle move through diffusion

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Diffusion

• movement of particles from an area of high
  concentration to an area of low concentration.
• Continues until an equilibrium is reached

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Osmosis

• Diffusion of water across a selectively permeable
  membrane.
• Occurs until water is balanced on both sides of
  the membrane.

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Membrane Proteins

• Facilitated diffusion a type of passive
  transport where proteins act as tunnels allowing
  larger particles to diffuse through with no
  energy.
• Active transport energy is needed to move
  particles.
• Carrier proteins change shape to open and close
  passages across the membrane.

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