Chapter 7 and 11 Membrane

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Chapter 7 and 11 Membrane Strunction
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Fluid Mosaic Model

• Fluidity
• P.Membrane (PM) held together by weak hydrophobic
  interactions
• Lateral drifting ability
• Lipids
• Proteins some stable/attached to cytoskeleton
• Temperature Dependent

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Mosaic

• Protein collage gt50 proteins
• Classes
• Integral Proteins
• Transmembrane proteins
• Penetrate hydrophobic core of membrane
• Peripheral
• Loosely bound to surface
• Attached to cyto-skeleton or ECM (Extracellular
  matrix)

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Review What organelles are responsible for
creating membrane proteins?
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Selective Permeability

• General rule like dissolves like
• Non-polar/hydrophobic solutes dissolve in lipid
• Ions and hydrophillic solutes dissolve in water
• Selective Permeability some substances can pass
  more easily than others
• CO2 , hydrocarbons, lipids, and O2 are nonpolar
  (can pass lipid membrane core easily)
• Water, glucose, sugars, charged ions (cannot pass
  lipid core easily) ? so must use hydrophillic
  transport proteins to pass (ex. Aquaporins)
• Small molecules are more permeable than larger
  ones

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Passive Transport

• Mvmt down gradient
• Spontaneous process ?G
• Types of Passive Transport
• Diffusion
• Osmosis
• Facilitated Diffusion

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Diffusion

• Diffusion molecules of any substance moves down
  gradient

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Osmosis

• Osmosis (tonicity dependent)
• Isotonic vs. hypotonic vs. hypertonic conditions
• Water always moves from hypotonic to hypertonic
  side

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Balancing Water Uptake

• Animals cannot tolerate change in tonicity
• Ex. Salt water fish vs. fresh water fish, vice
  versa
• Some Freshwater protists prevent lysing due to
  contractile vacuoles

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Balancing Water Uptake

• Plants Cell walls help maintain water balance
• Turgid Conditions Good!
• Flacid Conditions cause plasmolysis
• (lab 1E review)

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Function of Membrane Proteins

• Ex. Gap Junctions, Tight Junctions, etc.

• substrates bind to protein surface ? sends a
  signal within the cell to start a chemical chain
  reaction or cell response

• protein channels for passive transport
• protein pumps for active transport

• oligosaccharides on proteins or lipids act as
  name tags for cells.

• Catalysis of Chemical Reactions at the Membrane
  Surface

• Maintenance of Cell Shape

End of Slide Show
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Facilitated Diffusion

• diffusion of solutes (ions) with help from
  channel proteins in the plasma membrane

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Active Transport

• Movement against gradient
• Nonspontaneous, ?G, Requires ATP
• Types
• Protein pumps
• Cotransport
• Exocytosis Phagocytosis and Pinocytosis
• Endocytosis
• Receptor Mediated Endocytosis

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Active Transport generates an electrochemical
gradient charge difference (disequilibrium)
between both sides of the membrane
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Protein Pumps

• Ex 1 Sodium-Potassium Pump
• (take notes about the function of Na/K pump from
  the video)
• Sodium-Potassium Pump 3-D overview
• Ex 2 Pumping H ions into lysosome to create
  acidic envt

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Co-transport

• Involves the transport of a substance against a
  concentration gradient powered indirectly by an
  ATP powered pump

ATP
ADP Pi
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Exocytosis

• Fusing of vesicles to the plama membrane, thus
  releasing its contents

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Endocytosis

• The engulfing of substances by pseudopods
  extensions of the plasma membrane
• Three types
• Phagocytosis (cell eating lg. particles
  engulfed)
• Pinocytosis (cell drinking sm. ions and liquids
  engulfed)
• Receptor Mediated Endocytosis (use of surface
  proteins to engulf a specific substrate)

Back to Function of Membrane Proteins
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Signal Transduction

• 3 Stages of Signal Transduction
• Reception A ligand (analogous to a substrate)
  binds to receptor protein. Receptor proteins can
  be on the cell surface, but not always. Receptor
  protein changes shape
• Transduction Amplifies and sends the signal
  through chemical relay
• Cell Response Specific response is triggered

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Examples of Signal Transduction
Why is this hormone-receptor protein not found on
the surface of the plasma membrane?
Steroids and Hormones are types of lipids, which
can pass through phospholipid membranes easily.
Back to Function of Membrane Proteins