Cell Membrane

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Cell Membrane

• How does a cell move important chemicals across
  it?

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Cell Membrane

• Allows the cell to maintain homeostasis
• It is semi-permeable
• Cell chooses what enters and leaves the cells
• Structure is made of a lipid bilayer

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The Lipid Bilayer

• Hydrophobic region tails point in
• Hydrophilic region heads point out

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Kinds of Membrane Transport

• Diffusion
• Osmosis
• Facilitated Diffusion
• Active Transport

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Diffusion

• Molecules move from an area of High concentration
  to an area of low concentration
• Examples
• Smoke from fire
• Perfume
• Food coloring in water

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Osmosis

• Water moves from an area of High concentration to
  an area of Low concentration through a
  semi-permeable membrane.
• Osmosis

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Solutions

• Hypertonic the solution the cell is put in
  contains more of a substance than the cell
• So what happens?
• Hypotonic the solution the cell is put in
  contains less of a substance than the cell
• So what happens?
• Isotonic the concentration of the substance
  inside and outside the cell is equal
• So what happens?

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Facilitated Diffusion

• Diffusion that is helped across the membrane
• The membrane had protein channels that open up
  for larger molecules to pass in and out
• The movement of the molecules is still from high
  concentration to low concentration

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Active Transport

• Molecules move from an area of LOW concentration
  to an area of HIGH concentration
• Requires lots of energy
• active transport

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Other kinds of active transport

• Endocytosis a cell engulfs a large particle by
  wrapping itself around and reattaching the
  membrane
• Exocytosis a cell gets rid of a large particle
  by moving it to the membrane and squeezing it
  out.

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