A cell is a bag of chunky reactive soup

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• A cell is a bag of chunky reactive soup

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• Compartmentalization
• Scaffold of biochemical activities
• Selectively permeable barrier
• Transporting solutes
• Responding to external signals
• Intercellular interaction
• Energy transduction

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• Polar vs non-polar molecules
• Like dissolves in like
• Polar molecules dissolve in polar solvent and
  nonpolar molecules dissolve in nonpolar solvent
• soap

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• Cell membrane is a lipid bilayer
• Lipids in cell membrane are amphiphatic have both
  polar and nonpolar regions
• Cell membrane lipids will form a micelle in
  aqueous solution
• Liposomes are cell membrane lipids that engulf a
  molecule, i.e. DNA

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• Not everything in a cell membrane is a lipid!
• Cell membranes have proteins as well.
• Some proteins are embedded in the cell membrane
  integral proteins. Also known as transmembrane
  proteins.
• While other proteins are located on the outside
  cell surface peripheral proteins
• Lipid anchored proteins outside cell membrane can
  be found inside or outside a cell.

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• Carbohydrates (sugars) can be attached to both
  lipids and proteins in cell membrane.
• Called glycolipid and glycoprotein, respectively.

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• The lipids and proteins in the cell membrane are
  not fixed in position but constantly moving.
• The proteins move laterally within the cell
  membrane lateral diffusion
• While the lipids can move both laterally and
  rotate 360 degrees flip-flop diffusion

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Fluid Mosaic Model

• States that a cell membrane is a lipid bilayer
  with both peripheral and integral proteins.
• The proteins and lipids are moving and fixed in
  position.
• The current theory of cell membranes for the past
  thirty years.

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• The lipids in a membrane are organized into a
  liquid crystalline lattice.
• The lattice becomes a frozen crystalline gel at
  the transition temperature.

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