Cell Membrane

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Cell Membrane
2
Cell Membrane

• Phospholipid bilayer--two layers of phospholipid
  sheets.
• Phospholipids
• polar head --hydrophilic (water loving)
• non-polar--hydrophobic tail
• Like a bubble made of floating buoys.

3
Fluid Mosaic

• The membrane is permeable
• Protein and carbohydrates embedded in membrane
• Proteins act as receptors
• Carbohydrates can be cell identification tag.

4
Traversing the cell membrane

• Pair and share
• What substances must get into or out of the cell?
• Some possible answers carbon compounds (protein,
  carb, lipid), waste, oxygen, CO2, salts,
  minerals, water

5
Diffusion

• Solutes move from high concentration to low
  concentration, until they reach equilibrium.

6
OSMOSIS

• Special type of diffusion
• Water moves toward salt (solute)
• Diffusion of water through a selectively
  permeable membrane.
• What would happen to the water in cells if the
  blood becomes dehydrated (more salty)?

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How substances traverse the membrane
Osmosis
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• ANIMATIONS OF ALL PROCESSES
• Membrane Transport Graphic Organizer

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BULK TRANSPORT

• EXOCYTOSIS/ ENDOCYTOSIS
• COOLEST ANIMATION EVER
• WHAT CELL PARTS DO YOU NOTICE?
• COOL ANIMATION
• http//www.mhhe.com/biosci/genbio/espv2/data/cells
  /003/index.html
• CLICK ON 1.80 EXO/ENDOCYTOSIS

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Tonicity

• These terms are always used in comparison
• Draw a representation of each
• Isotonic solution
• Hypertonic solution
• Hypotonic solution

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Figure 7.14
Lowerconcentrationof solute (sugar)
Higher concentrationof solute
Same concentrationof solute
Sugarmolecule
H2O
Selectivelypermeablemembrane
Osmosis
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Work it Out

• What would happen to a blood cell in
• Blood Plasma?
• Pure water?
• Highly Saline (salty) solution?

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Figure 7.15
Isotonicsolution
Hypertonicsolution
Hypotonicsolution
(a) Animal cell
H2O
H2O
H2O
H2O
Lysed
Normal
Shriveled
Cell wall
H2O
H2O
H2O
H2O
(b) Plant cell
Turgid (normal)
Flaccid
Plasmolyzed
Osmosis
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Work it Out

• What would happen to a blood cell in
• Blood? Stays the same
• Pure water? Swells and bursts (lyse)
• Salt water? Shrinks --water leaves (crenate)

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Watch the Process

• See animations on Memory Stick
• Diffusion
• Osmosis
• Cell Transport