Cell Membranes, Diffusion, and Osmosis

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Cell Membranes, Diffusion, and Osmosis
dont have to write

• High to Low

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Cell membranes

• Present in all cells!
• Thin layer of lipid and protein that separates
  cells contents from its environment
• 5 to 10 nm thick
• 10,000 layers thickness of paper

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Phospholipids

• Draw it!

Polar
Nonpolar
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Philic vs Phobic

• Hydrophilic - Polar
• water loving
• Hydrophobic - Nonpolar
• water hating

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Draw in phospholipids
Polar
Nonpolar
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Dido . . . Try this one!
Nonpolar
Is this perfectly accurate? Why?
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What about the real thing?
Polar
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Phospholipid bilayer
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Diffusion

• Particles move from an area of high concentration
  to an area of low concentration (keyword
  equilibrium)

C
B
A
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A
B
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Osmosis

• The diffusion of water!

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Net Flow

• The way which a fluid flows

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Randomness

• Because diffusion depends upon random particle
  movement substances diffuse across membranes
  without requiring energy (good for cells/us)

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Selective Permeability

• Selective Permeability only some things can go
  through (size, shape, polarity, etc.)

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3 Types of Solutions
NaCl
H2O

• 1) Isotonic concentration of 2 solutions is the
  same

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• 2) Hypertonic one solution has a greater
  concentration of solutes

Which way will water flow?
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• 3) Hypotonic One solution has a lower
  concentration of solutes.

Which way will water flow?
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Osmotic Pressure

• Osmotic Pressure Osmosis puts pressure on the
  hypertonic side of a selectively permeable
  membrane
• Can be bad news for cells . . . Why?

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Ready for a lab?