Membranes and Passive Transport

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Membranes and Passive Transport

• Chapter 5
• Modules 5.12 -5.16

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The membrane is a fluid mosaic of phospholipids
and proteins
Module 5.12
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Proteins make the membrane a mosaic of function
Enzymes
Signal transduction
Transport
Module 5.13
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Diffusion
Diffusion is the net movement of molecules from a
region of greater concentration to a region of
lower concentration.
Diffusion is the tendency of particles of any
kind to spread out spontaneously to regions where
they are less concentrated.
Module 5.14
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Diffusion through a membrane
Module 5.14
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Concentration Gradient
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50
25
0
0
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The rate of diffusion is dependent on the
concentration gradient, the size of molecule, and
the temperature of the solution.
Temperature is a measure of the amount of energy
in the system increased temperature increases
molecular motion.
Module 5.14
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Osmosis

• Plasma membrane is permeable to water (a
  non-polar molecule)
• Osmosis is the diffusion of water through a
  selectively permeable membrane.
• Selectively permeable means some molecules can
  pass through membrane and others cant (size,
  charge, polar)
• Direction and rate of osmosis determined by the
  solute concentrations on opposite sides of the
  plasma membrane.

Module 5.15
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Solutions

• Solution Solute Solvent
• Concentration Solute/Solution solute
• Terms comparing concentrations
• Hypertonic (hyper higher tonos tension) the
  solution with the higher concentration
• Hypotonic (hypo lower) the solution with the
  lower concentration
• Isotonic (iso equal or same)

Module 5.15
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Osmosis
The movement of water is from the region where
there is more water to where there is less water.
Water moves from the lower concentrated solution
to the higher concentrated solution
Which side of the membrane has the most water
molecules?
Module 5.15
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Water balance between cells and their
surroundings is crucial to organisms
Module 5.16
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Question?
What would happen in a normally functioning
person who consumed a large quantity of hypotonic
fluid?